Mrfarb’s 2009 M1151a1 build thread

[mrfarb]

Figured I’d start a thread about my 1151a1 to keep all my junk in one place, easier to find anyway. First thread involved installing glow plugs:

Glow plug day for my 1151a1 rev

Yeah, I thought I’ll go out this morning and change the glow plugs out, shouldn’t be too difficult. No. Just no on the right side. I feel like this is what happens when you keep adding more and more features but don’t reengineer the simple basic maintenance items. Pretty much seems like I have...

www.steelsoldiers.com

Today, it’s time to recharge the a/c to test it. When I got the truck the a/c was non op - turned out the hose that connects front and rear evaporators had was laying on the exhaust and had a hole in it. Replaced that hose and the a/c dryer at the back.
Full admission, I’m not an a/c tech, but I’m handy and harbor freight is close by. I have an a/c tech to call though, which helps. So far so good! Hope there aren’t any other leaks. Going to keep vacuuming it for about 45 minutes.

 

[mrfarb]

First issue - condenser fans on right rear aren’t coming on, left rear are working.
Thought someone might be able to explain this - factory a/c front and rear. Just charging it, left rear cond fans run normal, right rear are not running - looked at wiring diagram and both are powered from the same relay. Has this happened before? Had to replace right rear fan assy, tested 437b and no power:

Edit - I have .24 volts at each 437b and 437c, so I’m guessing the relay isn’t good, but still not sure how I get power to left rear cond fans and not right rear.

 

[Mogman]

If both sets of fans are powered by the same relay and you have power to one but not the other than you must have a wiring issue.

 

[Mogman]

If you can post the schematic you are using so we can all see the same thing.

 

[mrfarb]

This is from an older thread:

 

[Mogman]

The power for the left side cond fans gets its power from the rear evap, not the rear cond relay, follow 416A

 

[Mogman]

Do you have a schematic of the rear evap?
The first thing I would do is see if there is power at 720A at the rear evap, should be hot all the time.

 

[mrfarb]

Of course, I see that now. No other schematics that I can find, but if the rear evap powers the left fans which are working, there must be a 437 wire at the front evap. I notice it’s missing from this schematic.

 

[Mogman]

No 437 comes from the cond relay, follow the numbers, 436 controls the relay coming from the low pressure switch.

 

[mrfarb]

I see, I need to pay better attention - time to give it a rest until tomorrow. Now that you say that I see - I need to confirm power is coming in to the relay at 445a and move backward from there. Thanks for the help.

 

[Mogman]

The power for the rear evap. and left cond. come from the other 30A breaker in the battery box,,, wire #720A, nothing to do with any of the 445(X) circuit at all.

 

[mrfarb]

The power for the rear evap. and left cond. come from the other 30A breaker in the battery box,,, wire #720A, nothing to do with any of the 445(X) circuit at all.

OK, bit of confusion on my part or yours - rear evap works perfectly, left cond fans work. It’s the right side condenser fan set that is inoperative.

 

[thoner7]

Ugh. I have to go through this for mine too, and I have no idea where to start. Please let us know what you find as you go through it.

This is from an older thread:

Please link the other thread if you don’t mind.

 

[mrfarb]

Ugh. I have to go through this for mine too, and I have no idea where to start. Please let us know what you find as you go through it.

Please link the other thread if you don’t mind.

Sure thing, when it’s fixed I’ll update, here’s the thread I got the diagram from:

OEM Air Conditioning Troubleshooting

With summer rolling around it’s time to get the A/C working. This is an 1152 ECV truck. Is there a TM that outlines the full circuitry and troubleshooting steps? So far I know the heater works, hi low fan works (albeit inversed, low is hi and hi is low). The only feedback I get from A/C...

www.steelsoldiers.com

 

[Mogman]

OK, bit of confusion on my part or yours - rear evap works perfectly, left cond fans work. It’s the right side condenser fan set that is inoperative.

AH, OK I am the one confused, nothing unusual about that

 

[Mogman]

So you need to check 415A at the relay and the feed 445A, if you have 24V at both of those then ether the relay is bad or the relay ground is bad.

 

[mrfarb]

Success! With Mogmans help learning how to read wiring diagrams, both condenser fan sets operate properly. So I finished charging the a/c! My next post tonight I’m going to give a step by step diagnosis and repair of my auction purchased m1151a1 a/c.

For fun here’s the temp reading from the registers when I was adding the last of the r134a - it since settled to about 58 degrees Fahrenheit.

 

[mrfarb]

Initial assessment- no Freon in the system, no activity from any component. All components present and connected properly
Step 1- attempted to vacuum system, system would not hold vacuum
Step 2 - assessment of system by adding Freon and looking for any leaks. Large hole located in hose connecting front and rear evaporators (located on right dash and center inside)
Step 3 - replace damaged hose and receiver/dryer (dryer contains dessicant to keep moisture out of system)
Step 4 - vacuum system for 45 minutes, then add r134a Freon- fault - right rear condenser fans inoperable, all other components functioning. Low voltage at wire 437b and 437c. No power from relay at 437a
Step 5 - using the above referenced wiring diagram, power noted at wire 445a to relay, traced the fault to the connector at the relay wire 445a. Removed connection and cleaned/repositioned connector - right rear fans activated
Step 6 - completed charging the system to 3lbs 8oz, approximately 4.6 12 oz cans of r134a

I purchased a gauge set, compressor powered a/c vacuum, and r134a at harbor freight to do this job as I’m not normally doing this kind of work.

 

[thoner7]

Thank you for this. It’ll be a few months before I can get to this but I need to go through the same process. I’m curious, can all those wires and relays be checked before adding any of the gas or vacuum? I’d probably let an auto shop do that part.

 

[mrfarb]

Thank you for this. It’ll be a few months before I can get to this but I need to go through the same process. I’m curious, can all those wires and relays be checked before adding any of the gas or vacuum? I’d probably let an auto shop do that part.

I see suggestions about shorting across relays, but honestly I think charging it to increase system pressures is the best way to test everything. Maybe get your auto shop to attempt to charge it - they will let you know if you have issues. If you have a good compressor at home the vacuum tool was only $15, that would at least tell you if you have a leak but you really need a gauge set too. A gauge set was $65 with 2 cans of r134a. May be cheaper than the shop charge for telling you it’s broken… not going to lie, there was a lot of personal satisfaction seeing all of it come to life myself.