New to forum, new m1008 owner, GEN 1 issue.

[weaponoffreedom]

I have read up on @Warthog very informative and GOOD info rich "CUCV Helpful" thread.

I have a no voltage brown exciter wire issue on GEN 1, and am tracking it down. The consensus is that if the bulb is burnt out, the GEN1 will not work. Seems silly why it would be that way, but it is what it is. Trying to plan my method of attack on this situation.

Is the instrument cluster connector connected or locate on the rear of the cluster circuit board?

Is the "firewall half connector" located behind the fuse box, or made into the rear of the fuse box?

I am not to terrible great at searching on this forum yet, any help would be appreciated. Thanks.

 

[weaponoffreedom]

I have read up on @Warthog very informative and GOOD info rich "CUCV Helpful" thread.

I have a no voltage brown exciter wire issue on GEN 1, and am tracking it down. The consensus is that if the bulb is burnt out, the GEN1 will not work. Seems silly why it would be that way, but it is what it is. Trying to plan my method of attack on this situation.

Is the instrument cluster connector connected or locate on the rear of the cluster circuit board?

Is the "firewall half connector" located behind the fuse box, or made into the rear of the fuse box?

I am not to terrible great at searching on this forum yet, any help would be appreciated. Thanks.

Also, would there be harm in just running a fused, and ingnition switched 12v supply to the alternator and bypass all that BS?

 

[vanaisa]

sorry, can not find this topic, where was talks about external alternator exiter.

 

[weaponoffreedom]

Any info would be great

 

[Barrman]

Welcome to the fun.

Yes the instrument connector in in the back of the gauge cluster. Treat it with respect and be very nice to it. The little copper tabs bend and break very easily. That by itself could be your problem source.

Yes the firewall plug is at the rear of the fuse panel. GM put some kind of black goo in there during assembly. It can ooze around and cause connectivity issues. Cleaning that plug is a very good idea.

I would suggest pulling the firewall plug apart before the gauge cluster. Use an Ohm meter to check connectivity between the plug and the exciter wire on the alternator. No connectivity, follow the brown wire until you find a break. Connectivity, check the plug pins and if they are good, dive under the dash.

 

[weaponoffreedom]

Welcome to the fun.

Yes the instrument connector in in the back of the gauge cluster. Treat it with respect and be very nice to it. The little copper tabs bend and break very easily. That by itself could be your problem source.

Yes the firewall plug is at the rear of the fuse panel. GM put some kind of black goo in there during assembly. It can ooze around and cause connectivity issues. Cleaning that plug is a very good idea.

I would suggest pulling the firewall plug apart before the gauge cluster. Use an Ohm meter to check connectivity between the plug and the exciter wire on the alternator. No connectivity, follow the brown wire until you find a break. Connectivity, check the plug pins and if they are good, dive under the dash.

Thanks, that seems like the simplest thing to start with. I did remove the bulb for the GEN1 today, and it has resistance, the "pod with tabs" that is sat in was not very clean......so cleaned it= continuity across the bulb now through the tabs.....still no light on GEN1, so at least that is out if the way.

Thanks again.

 

[weaponoffreedom]

Update.

Cleaned the firewall plug and ruled out supply to plug and plug to alternator.

Reconnected plug and battery..........got 7 volts at the exciter wire!

Why only 7.........?

 

[Barrman]

Is your resistor bypassed in the glow plug system? Was the 7 volts taken with the engine off and the plugs glowing?
Together you would have at most 10 volts with the engine off and the plugs glowing.

Since the only thing you did was the firewall plug and the alternator plug check. It seems checking the voltage at the diamond shaped engine harness buss next to the hydroboost should be your next step. Power for the 12 volt side of the truck comes from the starter motor and goes by red wire to the engine harness buss. Power then goes from the buss to the firewall plug. See if the passenger side and driver side studs are the same voltage.

 

[weaponoffreedom]

Is your resistor bypassed in the glow plug system? Was the 7 volts taken with the engine off and the plugs glowing?
Together you would have at most 10 volts with the engine off and the plugs glowing.

Since the only thing you did was the firewall plug and the alternator plug check. It seems checking the voltage at the diamond shaped engine harness buss next to the hydroboost should be your next step. Power for the 12 volt side of the truck comes from the starter motor and goes by red wire to the engine harness buss. Power then goes from the buss to the firewall plug. See if the passenger side and driver side studs are the same voltage.

Yes resistor is bypassed. 12 volt dedicated from battery to glow plug relay
Engine off, ignition on, wait light out (assuming glow was off at that point), 7 volts was read at brown wire 2 (wire connector) to alternator
12volts at diamond 12v buss, straight from battery, dedicated wire from battery with 30 amp fuse.

driver and passenger studs of the alternators? while running?

thanks

 

[Barrman]

OK. So you are now getting some voltage to the exciter wire but definitely not all that could be getting there. Since you went from 0 to 7 volts by just moving the 2 plugs. Can you unplug them both again and do an Ohm check on that brown wire from end to end? It still could just be a frayed wire that you accidentally moved into partial contact for a strand or three.

My thinking is the trouble is under the hood and until that is proven false by more checks there is no reason to pull the gauge cluster.

Keep in mind that once the exciter wire is figured out. There could still be an alternator internal issue that might be part of the problem.

 

[weaponoffreedom]

OK. So you are now getting some voltage to the exciter wire but definitely not all that could be getting there. Since you went from 0 to 7 volts by just moving the 2 plugs. Can you unplug them both again and do an Ohm check on that brown wire from end to end? It still could just be a frayed wire that you accidentally moved into partial contact for a strand or three.

My thinking is the trouble is under the hood and until that is proven false by more checks there is no reason to pull the gauge cluster.

Keep in mind that once the exciter wire is figured out. There could still be an alternator internal issue that might be part of the problem.

Thanks.

Copy on the "still might be the alternator thing"

Just trying to rule out as much as I can.

I did ordersome brand new bulbs. 194/168s Pulling a few bulbs, found one bad and the "bulb carrier clips" to be highly tarnished also.

I really need to get to the cluster connector, but would be difficult without pulling dash.

We will see. I will keep update, and again, thanks for your help and guidance.

 

[weaponoffreedom]

So, figured something out. I am not an electrical engineer so bear with me.

I found the issue to be that the bulb holders and bulbs had some corrosion on them. Depending on the "clocking" of the bulb holder in the socket, I obtained 12volts to the exiter wire, and the bulb would illuminate.

So for me, the issue was 2 things:

Firewall plug was nasty
corrosion issue on the bulb holder\bulb\circuit.

Still have not started the truck to see if it will charge front battery, but at least I am not getting 12 to the GEN1 and the light is coming on.

Thanks all for your help, both past and present!

 

[weaponoffreedom]

Also, Gen1 light is now on when the engine is running, so the saga continues. I suppose that means there is a fault with the alternator directly?

 

[Barrman]

Put a volt meter on the front battery with it running and see what voltage you get. Then go from there.

 

[weaponoffreedom]

Put a volt meter on the front battery with it running and see what voltage you get. Then go from there.

Identical to battery voltage 12.45 or so.....steady.

I was not expecting the alternator to not be putting out juice AND the exciter issue. Par for the course I guess.

I did not mention in the previous psot that the windsheild wiper sprayer magically started to work. I suppose that was due to cleaning the firewall plug.....an added bonus.

 

[Tow4]

Also, Gen1 light is now on when the engine is running, so the saga continues. I suppose that means there is a fault with the alternator directly?

If the light is on, the regulator should turn on with the engine running. Do this test to see if the alternator works: Alternator test on the vehicle.

 

[weaponoffreedom]

If the light is on, the regulator should turn on with the engine running. Do this test to see if the alternator works: Alternator test on the vehicle.

Also, just cleaned off all the grounds, and checked=1 ohm to battery......

When the exciter wire is hooked to the alternator, voltage drops from 12.5 to 2, is this normal operation? Red wire still has 12......

 

[weaponoffreedom]

So another update.......thanks all for your guidance and time.

After looking at all the data brought forward to me........I went back out in the building....I had left it running for a bit just to get it warmed up. Anyway, the GEN1 light was still on.....just out of "just because" hit hit the accelerator pedal.......AND THE LIGHT WENT OFF!......I stopped and thought "well surely that had no good effect" (like maybe the bulb burnt out).......got my DVM and went to the GEN1, and BOOM, 14.68v.....went to the back battery,......29.1 volts!......front battery 14.54 volts!

The guy I bought it from said that he had some trouble with the alternators, but had "fixed" it. Of course, going into this, I did not understand that this was a known common issue.

Really without the knowledge from this site I and many would be lost!

Anyway, it ran for a bout 15 min.....key off.....restart.....and boom, the lights go out and everything appears to be normal.

I wonder if the first alternator ha not been working for a decade, and something was just "stuck" and engine rpms fixed it?

I did do quite a bit of wiggle test on the harness prior to with no result, at the beginning of this process. It seems the direct effect of raising RPMs for a moment made everything right.

Any thoughts on this craziness?

 

[deank]

That is how they work, always have. I do not know why. Worked the very same way when I drove them on active duty in the 80s.

 

[weaponoffreedom]

That is how they work, always have. I do not know why. Worked the very same way when I drove them on active duty in the 80s.

mind elaborating on this.??