10 kw generator mep 803a

[kloppk]

What year is your gen?

It's a 1994 and came with the quad winding fuse mod already installed in it.

A MOV only reacts to spikes of milli second duration, not at all to steady state voltages,

I respecfully have to disagree. MOV's conduct in the presence of both voltage transients and steady state voltages.

...so the best thing it would do is over heat and catch fire.

I believe you may have misunderstood where the MOV would be in the circuit. By having the MOV installed "after" the 3 amp fuse it would simply cause the fuse to pop and long before the MOV ever started to heat up. Once the fuse pops the quad voltage is removed from the MOV and the regulator.
I'd be using a MOV rated at ~250V which is well above the typical 90 v on the quad windings.

 

[m-35tom]

It's a 1994 and came with the quad winding fuse mod already installed in it.


I respecfully have to disagree. MOV's conduct in the presence of both voltage transients and steady state voltages.


I believe you may have misunderstood where the MOV would be in the circuit. By having the MOV installed "after" the 3 amp fuse it would simply cause the fuse to pop and long before the MOV ever started to heat up. Once the fuse pops the quad voltage is removed from the MOV and the regulator.
I'd be using a MOV rated at ~250V which is well above the typical 90 v on the quad windings.

Yes everything you say is right, but just putting a load on the circuit to reduce the voltage is not the best solution, MOVs are not used for things like this, and how do we really know that a 3 amp load is not going to eventually cause some issues? Also you now have a variable load on the circuit used for voltage sensing, so the reg may not hold a set voltage well. Gen sets that are relatively new compared to yours do not have the fuse, apparently some other mod to the reg has been made.

 

[kloppk]

In looking at the fuse mod in my genset it appears to be done exactly per TB 11-6115-741-24 chapter 5.2.
According to the TB all MEP-802,812,803 & 813's get the fuse mod during the Tier 1 & 2 resets which explains why newer gensets would not have have the fuse mod yet.

Adding the MOV across the 7 & 8 will draw less than 0.0005 A (not 3 amps) which is insignificant to the load the regulator draws from quad windings.

 

[zarathustra]

This is in response to a posting a few posts ago...

I went to the shop and checked the voltage regulator circuit board on my ~2000 mep 803a unit. The board number is 19583 H. The 2009 board that you have is also a 19583, but I wonder about the detail designation of 'H'. What is the detail letter on your board? If you have a letter later than H then I'd be really, really interested in knowing what the number on the two MOSFET transistors is, as well as the diode number that is between pins 5 and 6. The diode will likely be 1n504 or 1n506.

I found the fuse modification a little confusing....

One version shown on this site is a 3 amp slow blow 250 vac setup. I can't find any referenced manual or service bulletin associated with the version here on steelsoldiers, but the form it was on along with the green voltage regulator looked official - sorta...

The second version in the TB 6115-741-24 calls out for a 3 amp slow blow fuse rated at 600 vac. That is a much larger (physically) fuse than the 250 vac version. It calls for the same 600 vac rated fuse on the 802a - at least the 816a and possibly beyond that.
It, also uses the green voltage regulator in its visuals.

I'm going to opt for the 250 VAC smaller version of this modification. If I am wrong in choosing that all it should mean is that I will possibly have a blown fuse for no apparent reason. If that becomes a problem then I'll switch to the 600 vac rating

 

[bullwhacker]

HHHEEEELLLLPPPPP...

Sorry for long delay; work took me away all this time.
Recap I have a MEP 803a TQG.
Every time I turn the Master Switch from the off position the CB1 breaker trips.
I replaced the master switch with the "newer" one and the CB1 still trips.
I can turn it to the preheat and the CB1 breaker doesn't trip and I can turn the panel lights on and off while the master switch is off.
I "hot wired" to start and run the generator.
The Hz meter works, I have 120v at the power plugs on the out side of the panel, charging circuit works and juice is going to the batteries and are charging..
NO test lights on the panel.
I even disconnected both fuel pumps and float sensor; nothing changes.
Something after the CB1 is causing it to trip.
What circuit are after this DC Circuit?
What leads go to each of those circuits?
Everything is in white colored wire.
I do see the voltage meter flicker up to read a voltage then dies as soon as the CB1 breaker trips.
Is there a circuit that is common to power the meters and or a relay?
I am considering carefully of hooking my meter to the ac output lugs and applying 24v to the contactor switch for a few second to see if the contactor energizes and I have ac voltage at the output lugs.
I know the gen head is okay given even hot wiring to start and run the generator it is getting flashed.
Anyone have this problem and what was done to fix it?

 

[zarathustra]

It would seem that if there is a short it would be on one of the pins 1,3,5,7 on S1. Since the glow plugs won't trip the breaker, then pin 1 is likely OK. So, if you disconnect pins 3,5,7 on S1 and turn s1 on you can see if CB1 trips. If it doesn't, then connect pins 3,5,7 one at a time and see which pin causes the breaker to trip.

However, since you said that as soon as you turn the switch on it trips, I'd suspect the short is on either pin 3 or 5 -- if I had to pick the most likely pin between 3 and 5 I'd choose pin 5 as the culprit. Now, that is without seeing the unit..

Once you isolate which pin it is on S1 you can further trace it down to the specific component.

I've fouind that things are mis-wired more often that one might think, so check each wire number on S1 against the schematic to make sure that only the wires specified for that pin on the switch are connected to it. Any superfluous wires connected to the switch should be disconnected and re connected to whatever component they belong to...

Note -- I wouldn't "hot wire" around a circuit breaker that trips -- it is tripping for a reason -- and a circuit breaker is there to prevent fires.

 

[bullwhacker]

Thanks for the info; I will try it this weekend and give an update.
I haven't hot wired around the CB1.
I just setup a switch and fused wiring to energize the fuel pump and stop solenoid and use the crank switch to turn it over to fire it up; then flip it back to normal.
Everything is dead on the panel except the Hz meter, power plugs on the outside they work fine. The master switch is left in the off position.

It would seem that if there is a short it would be on one of the pins 1,3,5,7 on S1. Since the glow plugs won't trip the breaker, then pin 1 is likely OK. So, if you disconnect pins 3,5,7 on S1 and turn s1 on you can see if CB1 trips. If it doesn't, then connect pins 3,5,7 one at a time and see which pin causes the breaker to trip.

However, since you said that as soon as you turn the switch on it trips, I'd suspect the short is on either pin 3 or 5 -- if I had to pick the most likely pin between 3 and 5 I'd choose pin 5 as the culprit. Now, that is without seeing the unit..

Once you isolate which pin it is on S1 you can further trace it down to the specific component.

I've fouind that things are mis-wired more often that one might think, so check each wire number on S1 against the schematic to make sure that only the wires specified for that pin on the switch are connected to it. Any superfluous wires connected to the switch should be disconnected and re connected to whatever component they belong to...

Note -- I wouldn't "hot wire" around a circuit breaker that trips -- it is tripping for a reason -- and a circuit breaker is there to prevent fires.

 

[bullwhacker]

After a delay work caused I was able to check and try your suggestion.
I found number #3 to cause CB1 to trip.
I left it disconnected and I could hear the fuel pump now run with switch in the first 12 o'clock position.
Pump stopped at the second position and when I turned it to start I could hear the start relay in the relay bank in front of me click and I saw it move; but no cranking.
Panel also was still dead except for the panel lights..
I moved the number 5 to the number 3 switch connection to test and now both pumps at either switch position runs.
I pulled the start relay from the bank and turned the switch again to the start position; I could hear another relay click some where??
Also the engine fuel pump run/stop solenoid didn't energize either.
Out came my switch and button box with leads.
I hooked to a 24v hot from the starter solinoid; hooked u to the run/stop solenoid ; push button with 24v white lead for the pull; switch to red lead for the hold and another push button to starter crank lead on the solenoid.
Flipped the switch for the red hold lead and momentary push the button for the white pull lead. Solenoid snapped back and held; hit the crank button with the maintenance switch in the normal position and generator fired up.
As mentioned panel still dead except the Hz meter and panel lights.
I also have 120v at the external convenience plugs. and test panel malfunction panels is dead also.
I am looking at the schematic and figuring things out or I think so; any helpful suggestions??

 

[zarathustra]

First, re-connect everyting to its original position on the switch except leave pin 3 disconnected. Since when you have the switch in the first position that includes the auxillary fuel pump you hear a pump working - that is the E1 pump, the auxillary fuel pump. When you move to the next position, that fuel pump should stop -- which it does correctly.

Now, I looked at the schematic and I see that pin 3 has several items connected to it which includes the E2 pump (the internal fuel pump) and a diode shunting it, I'd suspect either the pump or more likely the diode. That would be easy to check by re-connecting pin 3 to the switch and removing the K12 relay. Don't try to start it in that position, just turn the master switch to the third position and see if the breaker pops. If the breaker DOES NOT pop then there is a short in either the wiring to the main pump, the main pump or the diode. I ALWAYS suspect diodes first. Note that when you do this test the main (internal) fuel pump will NOT try to come on -- that is "normal" since relay K12 was removed for the test.

The way to check a diode is to disconnect one side of the diode and connect an ohmmeter across it. Then test it again with the meter leads swapped across the diode. One direction should read low resistance whilst the other side should read a high resistance. If the diode is shorted then it should read low resistance in both directions.

A second way to check the diode would be to re-install relay K12 and disconnect one side of the CR5 diode. Either side of the diode would be Ok to disconnect. Then turn the switch to the third position. If the breaker DOES NOT pop then the diode is bad, if it does pop then the diode is good and should be re-connected. Don't try to start it with the diode disconnected - the diode is in there for a reason..

It is probably a 1N504 diode -- that is a common diode and is what they use (mostly) in these units.

Look at the schematic --- page 276 of the 803a manual ( You'll have to enlarge it to around 1200% in order to see the drawing) -- make sure that the diode is connected properly -- there is a diagram on the diode and the arrow should be pointing AWAY from ground, and towards the voltage source (from K12) that powers the pump.

There are other components in that circuit, but the pump and the diode would be the first things I'd check.

Note that the warning lights get their power from pin 3, so it is 'normal' for them not to work when the circuit breaker is popped.

 

[bullwhacker]

Thanks much for the information.
I will check your suggestion next weekend.
I forgot to mention I did pull the plugs at both fuel pumps and float sensor on main tank and the CB1 still popped.
This sounds stupid but where is that other relay I could hear clicking ( somewhere in the generators bowels ) when I pulled the start relay out?
Also where physically is that diode(s) located?
Jeez I've never encountered so many rusted little bolts in my life to have to remove panel(s) just to get to something - Thank God for my Ryobi 3rill impact driver and liquid wrench.
I am also curious why everything is wired with WHITE WIRE and mini leters and number to ID them? Color coding would have been allot better or was it about it "falling in enemy hands" kinda thing?

First, re-connect everyting to its original position on the switch except leave pin 3 disconnected. Since when you have the switch in the first position that includes the auxillary fuel pump you hear a pump working - that is the E1 pump, the auxillary fuel pump. When you move to the next position, that fuel pump should stop -- which it does correctly.

Now, I looked at the schematic and I see that pin 3 has several items connected to it which includes the E2 pump (the internal fuel pump) and a diode shunting it, I'd suspect either the pump or more likely the diode. That would be easy to check by re-connecting pin 3 to the switch and removing the K12 relay. Don't try to start it in that position, just turn the master switch to the third position and see if the breaker pops. If the breaker DOES NOT pop then there is a short in either the wiring to the main pump, the main pump or the diode. I ALWAYS suspect diodes first. Note that when you do this test the main (internal) fuel pump will NOT try to come on -- that is "normal" since relay K12 was removed for the test.

The way to check a diode is to disconnect one side of the diode and connect an ohmmeter across it. Then test it again with the meter leads swapped across the diode. One direction should read low resistance whilst the other side should read a high resistance. If the diode is shorted then it should read low resistance in both directions.

It is probably a 1N504 diode -- that is a common diode and is what they use (mostly) in these units.

Look at the schematic --- page 276 of the 803a manual ( You'll have to enlarge it to around 1200% in order to see the drawing) -- make sure that the diode is connected properly -- there is a diagram on the diode and the arrow should be pointing AWAY from ground, and towards the voltage source (from K12) that powers the pump.

There are other components in that circuit, but the pump and the diode would be the first things I'd check.

Note that the warning lights get their power from pin 3, so it is 'normal' for them not to work when the circuit breaker is popped.

 

[bullwhacker]

zarathustra again many thanks for your help.
I've looked at the manual again and the CR5 diode you mentioned; is it on the resistor diode board shown in the manual inside of the control box?
Also which is the K12 relay? Is there a "K12" on it or by the socket in the relay bank show in one of my previous pictures?
Also looking at the schematic and item L5 the solenoid for engine run and shutdown the lead "C" ground on the diagram line from gram is written CR!; is that a diode?
From reading the manual it kinda states on the diagram "CR" is a diode. I ask because there is no diode symbol and if it is a diode which way is it supposed to face? Towards the solenoid so 24v can get to it to fire it to initiate the pull?
I figured from you directions if I couldn't figure out where the "K12" relay is; I'd pull one side of the CR5 diode you mentioned and see what happens.
I've done "some" work on "civilian" generators; but I have never seen so many "safety" interlocks on a generator until I started to work on "military" generator. Is this to keep the generator from being destroyed by "accident" through ignorance or carelessness?
Again many thanks for your help and directions.....

 

[TurboJoe]

I also have to wonder if the 'input power' (3 + 4) and the 'quad' (8 + 7) are not misunderstood. In a 3 phase gen with an unbalanced load like this could be in single phase, it is very hard to have a voltage regulator since the load could be high on the windings you use for referance voltage so the reg would send the field more voltage. If that winding comes up to correct voltage, other windings with less load will be too high. To avoid this you have a seperate winding with no load, like the 'quad' winding, and take your ref voltage from it. Then you have the input power to run the reg from some other coil, it would not matter which. Apparently, however, the diodes that fail are in the quad circuit, I do not really understand why yet, I would think the reg would get it's DC voltages from the input power.

I was trying to bench test the AVR from a unit that had the control wiring catch on fire. I did the old light bulb test, and used a variac to change the voltage input to the quad terminals (7,8, ) and ran constant 120v to the power terminals.

I was able to see the AVR vary the field current with the changes in input voltage to the quad, except it seemed backawards to what I'm used to. If I turned the voltage up, the bulb got brighter. This makes no sense as every generator I've worked on would want to lower the field current when the voltage rose, and increase the field current when it dropped. I also tried varying the power (labeled sense circuit on the AVR) and that didn't have an effect on the field. Perhaps they both need to move to test efficiently? I really may just scrap this AVR all together and use a commercial unit off my shelf, and just hook it up to the quad winding and the field winding.

 

[zarathustra]

The relay K12 is the second from the left --

If you open the control panel you'll see a string of 6 relays. The K12 relay is the second from the left. Be sure the unit is turned OFF before removing the relay and that it is OFF when replacing the relay..

Diodes will all be CR, followed by a number which identifies it in the schematic. Usually the diode will have a stripe on one side identifying the polarity of the diode. It should have a diagram that has an arrow pointing to a line on it as well.

CR5 is the diode that is shunted across the E2 pump.

 

[zarathustra]

I would be surprised if one could substitute a different voltage regulator successfully.

The quad winding supplies the AC that powers the regulator -- that's all it does, and it uses a permanent magnet for excitation. Think of it as a "fourth" phase/winding -- hence the name "QUAD". Its only use is for regulator power. That AC is rectified within the voltage regulator box and powers the Mosfets and the chip et al in the regulator. The DC output of the regulator is to the F1,2 exiter stator which is converted to AC in the exciter rotor which is further rectified back to DC by the rotating diodes in the rotor to excite the AC generator. The AC from phase 3 is sampled and inputs to the regulator on the SENSE terminals. Since the Quad winding has a permanent magnet, none of the changes in the excitation voltage will have any effect on it's AC output.

It may seem convoluted and odd, but that is the only way to do it if one wants a brushless generator.

Since this particular regulator is designed to work with this particular ONAN exciter, rotor and stator I'd think that any other regulator would be a mismatch and may either not work at all, or be unstable, or perhaps work opposite from what one might expect..

The voltage regulator can be repaired -- you'd have to drill out the rivets and from there you are on your own since I don't know of any schematic of the regulator, and whilst I'm sure there is one, it is probably proprietary and not available to the general public. I started to draw one, but lost interest in the project. In the regulator I repaired I found one shorted MOSFET and one shorted diode. I replaced both MOSFETS 'cause I didn't want to have to get into the regualtor a second time.

I've drawn up a set of block diagrams in power point detailing the pins and in some cases, wire numbers for the AC interrupt, the voltage selection switch, and the regulator inputs. In the next few weeks I'll be posting them on the web --I've just got to get some free time... I did these mostly for myself since I was fighting a thorny problem which turned out to be a miswired stator wire on the voltage selection switch.

I'd recommend that anyone that is having trouble with power generation begin by FIRST verifying that all the wires on the selection switch are in their proper place. Also I'd recommend that anyone starting one of these TQG's for the first time have the voltage selection switch in the 3 phase position. Many of the "opportunities for error" have been eliminated by the switch being in the 3 phase position. Once that one has determined that the generator is working properly in 3 phase he can select one of the other two positions and work through them...

 

[bullwhacker]

The relay K12 is the second from the left --

If you open the control panel you'll see a string of 6 relays. The K12 relay is the second from the left. Be sure the unit is turned OFF before removing the relay and that it is OFF when replacing the relay..

Diodes will all be CR, followed by a number which identifies it in the schematic. Usually the diode will have a stripe on one side identifying the polarity of the diode. It should have a diagram that has an arrow pointing to a line on it as well.

CR5 is the diode that is shunted across the E2 pump.

Hey Thanks again.
Jeez I spent an hour unscrewing ALLOT of rusted small bolts with rusted nuts on the backside of bulkheads and in places I've never dreamed I'd have to jam my hand.
I also pulled the panel in the back where the fuel pump is at the tank.
Think I did finally find and you confirmed the K12 relay was the one I mentioned was moving when the master switch was turned to start position.
I did the tests you mentioned except for the CR5; have not found it yet?
The CB1 always popped with the relay either installed or taken out. I did find a diode on a terminal strip behind the malfunction panel in another compartment behind the control box compartment.
You can see the location of the diode in the picture. I did pull the diode thinking it might be the CR5 and CB1 still popped. I tested the diode both leads and appears to be good.
NOW the fuel pumps are not running; tested leads no voltage and tested pumps - they work.

http://i58.tinypic.com/e63e9u.jpg
Picture taken of control box and compartment behind it. The terminal strip has a diode on it; Is it the CR5?

http://i57.tinypic.com/2hnb0r5.jpg

http://i59.tinypic.com/zlw6d.jpg
Picture of control box from the top showing the relays and the one you mentioned "K12" is the second one from the left.
Upper left corner is that infamous CB1 breaker and the Fuse which is okay. Bottom middle yo can see the edge of the new master switch that was installed.

I looked at the # 3 circuit again and saw it also went to the exciter on the alt. I disconnected that just to see and turned the master switch to r/p no CB1 popping - yaa; Tried to start when turned to the start position; motor just grunted and CB1 popped???
Now it sill pops with he exciter disconnected and no more action when trying to start, just the relay in the rear compartment - silver one metal case; so I reconnected the exciter wire..
If that diode wasn't CR5 I still will have to find it and if it was then I am thinking either some one hooked something to direct ground and a dead short and an "accidental" short some where from worn what ever?

P.S. My phone takes great pictures; no it isn't an iphone...

 

[zarathustra]

Well, you just eliminated about a third of that circuit as being the problem. At this point leave CR5 alone since it isn't causing the "pop" of the breaker.

What you might do next is to swap the K12 relay with the one next to it (to the right not left) just to make sure that the relay itself isn't bad somehow. The relay to swap with is the one to the right of K12, NOT the one to the left. The one on the left is the starter/field flash switch and that is unique - there is only one of them in the unit.

The other five relays are identical.

The "stuff" in the back of the unit in your picture consists of the AC contactor which is the square thing that has the heavy wires on it and the voltage selection switch. That diode is not CR5. None of that "stuff" back there will be your problem -- it is all best left alone at this point since it is the high voltage section and it isn't going to work until the "pop" problem is solved.

I'm out of town right now; about 200 miles away from the schematic that I use, so I can come up with another idea or two on Monday....

z

 

[TurboJoe]

I would be surprised if one could substitute a different voltage regulator successfully.

The quad winding supplies the AC that powers the regulator -- that's all it does, and it uses a permanent magnet for excitation. Think of it as a "fourth" phase/winding -- hence the name "QUAD". Its only use is for regulator power. That AC is rectified within the voltage regulator box and powers the Mosfets and the chip et al in the regulator. The DC output of the regulator is to the F1,2 exiter stator which is converted to AC in the exciter rotor which is further rectified back to DC by the rotating diodes in the rotor to excite the AC generator. The AC from phase 3 is sampled and inputs to the regulator on the SENSE terminals. Since the Quad winding has a permanent magnet, none of the changes in the excitation voltage will have any effect on it's AC output.

It may seem convoluted and odd, but that is the only way to do it if one wants a brushless generator.

Since this particular regulator is designed to work with this particular ONAN exciter, rotor and stator I'd think that any other regulator would be a mismatch and may either not work at all, or be unstable, or perhaps work opposite from what one might expect..

The voltage regulator can be repaired -- you'd have to drill out the rivets and from there you are on your own since I don't know of any schematic of the regulator, and whilst I'm sure there is one, it is probably proprietary and not available to the general public. I started to draw one, but lost interest in the project. In the regulator I repaired I found one shorted MOSFET and one shorted diode. I replaced both MOSFETS 'cause I didn't want to have to get into the regualtor a second time.

I've drawn up a set of block diagrams in power point detailing the pins and in some cases, wire numbers for the AC interrupt, the voltage selection switch, and the regulator inputs. In the next few weeks I'll be posting them on the web --I've just got to get some free time... I did these mostly for myself since I was fighting a thorny problem which turned out to be a miswired stator wire on the voltage selection switch.

I'd recommend that anyone that is having trouble with power generation begin by FIRST verifying that all the wires on the selection switch are in their proper place. Also I'd recommend that anyone starting one of these TQG's for the first time have the voltage selection switch in the 3 phase position. Many of the "opportunities for error" have been eliminated by the switch being in the 3 phase position. Once that one has determined that the generator is working properly in 3 phase he can select one of the other two positions and work through them...

My thought was to abandon the quad winding and use 4 wire standard auto voltage regulator.. I have them in 5,8,10,20amp current capacities for the field. It would not be as robust as the current design but I'd imagine it would work just fine. I think the regulator I have works as it does make a field and modulate the field. I'll try that first then take measurements and then decide if I can use an off the shelf AVR.

 

[bullwhacker]

Well, you just eliminated about a third of that circuit as being the problem. At this point leave CR5 alone since it isn't causing the "pop" of the breaker.

What you might do next is to swap the K12 relay with the one next to it (to the right not left) just to make sure that the relay itself isn't bad somehow. The relay to swap with is the one to the right of K12, NOT the one to the left. The one on the left is the starter/field flash switch and that is unique - there is only one of them in the unit.

The other five relays are identical.

The "stuff" in the back of the unit in your picture consists of the AC contactor which is the square thing that has the heavy wires on it and the voltage selection switch. That diode is not CR5. None of that "stuff" back there will be your problem -- it is all best left alone at this point since it is the high voltage section and it isn't going to work until the "pop" problem is solved.

I'm out of town right now; about 200 miles away from the schematic that I use, so I can come up with another idea or two on Monday....

z

No problem your help has been tremendous.
I was aware that compartment is the high voltage section; but I needed to find out what kind of relay was clicking back there when I turned the master switch to start; is it the disconnect starter relay?
I looked for this terminal strip in the diagram and couldn't find it as the others you can see in the control box.
That #3 lead coming off of the switch goes to a terminal strip and on the side opposite of it two wires are attached.
I did a test when I turned the switch to the preheat and got 24v on the big leads and again no CB1 popping.
I was going to label where that diode I mentioned on the terminal is and what for; as any other diodes found.
The battery charging alt. I forgot to mention is on the output side two leads thin wires are there and two other terminals right near it is not used?

 

[TurboJoe]

The two relays in the back are the glow plugs, and the starter relay. When you turn the key to start the clicking you hear would be the starter relay.

 

[zarathustra]

Back to the 803a...
With K12 back in place, remove K19--That would be the second from the right relay, and see if CB1 pops.
If not then the problem is in the float switch circuitry and we can isolate it further.
If the breaker still pops, replace K19 and disconnect the connector going into the warning light unit A2. It is a white-ish connector that goes into the back of the unit
If the breaker still pops, replace the connector on A2 and disconnect the wires on the meters one at a time as follows:

Step A ----- Pin I of M7 (Oil press gauge) wire number 137J
Step B ----- PIN I OF M6 (temperature gauge), wire number 137H and 137J
step C ----- Pin I of M5 (fuel level gauge), wire number 137F and 137H
Now, when disconnecting these wires, do all the tests one at a time and note the results.
So, do step A and test, then re-connect Pin I of M7 and do step B
Reconnect pin I of M6 and and do step C
Reconnect pin I of M5
Now, if you note if any extra wires are on Pin I of those three meters OR that the wire numbers that are on pin I of those meters is anything other than what is above. Also note that those wires should be on pin I and not any other pin on the (respective) meter
Let's see if any of the above tests do anything....

None of the above tests will tell us which component is bad, but one of those tests should narrow it down to only a few possibilities