Air conditioning

[thoner7]

Is there a diagnostic chart in a TM for the ECV style AC system? Specifically the rear AC units like in the 1165 or 1151?

The rear unit doesn’t work at all, and the fan for the front unit blows air but not cold air.

Lastly, do these units use common enough parts where any old auto shop could recharge it? Or potentially fix whatever is wrong if it’s above my head?

 

[justinn]

There is a drawing floating around here(it might be for the 1114) that shows the layout for the system. It's actually very straightforward as there are only a few wires that run to that box. My rear blower failed and I am currently in the process of replacing it. Most of the blowers that I found are big rig replacements, but they should work perfectly fine and as best as I can tell, I will need to make an "adapter plate" out of ABS plastic to get it to work. I bought 2 different squirrel fan setups to see if I can shoehorn the larger one in there(it's quieter). You will see that some of the squirrel fans are actually "3 speed". Don't put too much thought into that as you can just choose which speed you want and wire it as such. Or you can just eliminate the resistor setup altogether.

If you follow the plug from the rear box up to the front, you can inspect the wiring along the way. Mine was fine, but there were some places that it would have rubbed through in another couple of years.

Does your compressor engage when you flip the switch? Is the system fully charged? Have you checked all of your grounds?

Justin

 

[MarkM]

What is this "air conditioning" you speak of ?

Lol

Mark

 

[Autonomy_Lost]

FYI, my front unit wasnt blowing cold air. Turned out the AC was fine, but the valve for the heater core was stuck in the open position so it was running heat and AC at the same time. Easy fix.

And yes, anyone with standard equipment should be able to diagnose and recharge the AC.

 

[thoner7]

I have not really looked at any of it. And my knowledge of AC systems is about zero. I was searching for the TM first. But, the box in the back seat, there’s one black hose connected, and another opaque hose that is missing a hose clamp and should be connected to an elbow. And the fan didn’t come on.

 

[justinn]

FYI, my front unit wasnt blowing cold air. Turned out the AC was fine, but the valve for the heater core was stuck in the open position so it was running heat and AC at the same time. Easy fix.

And yes, anyone with standard equipment should be able to diagnose and recharge the AC.

ah yes... easy to bypass the mixing valve. I just popped mine up and reset it into the holder again in the forward position(IIRC) that kept it closed. The engine alone generates enough heat for most of our winters here in central Texas. Worst case scenario, I pop it back in the other position if it gets below freezing. Those switching valves seem to be prone to failure anyway....

Justin

 

[justinn]

I have not really looked at any of it. And my knowledge of AC systems is about zero. I was searching for the TM first. But, the box in the back seat, there’s one black hose connected, and another opaque hose that is missing a hose clamp and should be connected to an elbow. And the fan didn’t come on.

The white/opaque hose you speak of, should just be the drain. Probably need to break out 'ye ol' test light and make sure you are getting power back there. my rear blower had lost some fins on the fan. Although it would kick on, it vibrated to high heaven and eventually shook the ground wire right off of the blower motor.

These systems are pretty simple as far as A/C systems go.

Justin

 

[Autonomy_Lost]

ah yes... easy to bypass the mixing valve. I just popped mine up and reset it into the holder again in the forward position(IIRC) that kept it closed. The engine alone generates enough heat for most of our winters here in central Texas. Worst case scenario, I pop it back in the other position if it gets below freezing. Those switching valves seem to be prone to failure anyway....

Justin

I opted to install the manual "cable type" valve from an m998 that I can control it from the cab manually.

In a pinch, you can use a 1/2 pex ball valve.

 

[Retiredwarhorses]

The rear evaporator only runs if the compressor is running, same goes for the condenser fans…your AC needs to be evacuated and properly charged. The front unit is an evaporator/heater unit like any other automobile, the rear is A/C only.
Troubleshooting cannot commence till the required 3.8lbs of r134a is installed

 

[Autonomy_Lost]

Do yourself a favor and invest $200 in a vacuum pump and set of AC gauges. Watch 20 minutes of youtube and you will have the tools and skills to troubleshoot this issue and anytime you have AC trouble with other vehicles in the future. Honestly its not that complicated.

 

[Retiredwarhorses]

Do yourself a favor and invest $200 in a vacuum pump and set of AC gauges. Watch 20 minutes of youtube and you will have the tools and skills to troubleshoot this issue and anytime you have AC trouble with other vehicles in the future. Honestly its not that complicated.

sure, that’s great for just recharging a system and everything behaves as it should, unfortunately thats not the case on so many of these torn apart USMC truck, I spend hours on the phone with AC shops instructing them on nuances of this system,

 

[Autonomy_Lost]

sure, that’s great for just recharging a system and everything behaves as it should, unfortunately thats not the case on so many of these torn apart USMC truck, I spend hours on the phone with AC shops instructing them on nuances of this system,

Sure, it can get complicated. But in my experience many problems come down to leaks. If you can get good at finding and repairing leaks, and then properly recharging, its a good foundation for fixing many issues.

 

[HoveringHMMWV]

The rear evaporator only runs if the compressor is running, same goes for the condenser fans…your AC needs to be evacuated and properly charged. The front unit is an evaporator/heater unit like any other automobile, the rear is A/C only.
Troubleshooting cannot commence till the required 3.8lbs of r134a is installed

Excellent and well timed info as the rear a/c on my M1151A1 has started cycling on/off at somewhat irregular intervals. The rear evaporator fan has started cycling on/off at short intervals (20 - 30 secs) with the compressor (confirmed visually) along with the left rear condenser (audibly along with a jump in the voltage gauge). I had read that a bad start box could be the problem but had a NOS matching spare that did not solve the problem when swapped out. Now off to find an a/c service shop to confirm. Seems to be blowing very cold when operating so I may have over serviced earlier.

 

[justinn]

Excellent and well timed info as the rear a/c on my M1151A1 has started cycling on/off at somewhat irregular intervals. The rear evaporator fan has started cycling on/off at short intervals (20 - 30 secs) with the compressor (confirmed visually) along with the left rear condenser (audibly along with a jump in the voltage gauge). I had read that a bad start box could be the problem but had a NOS matching spare that did not solve the problem when swapped out. Now off to find an a/c service shop to confirm. Seems to be blowing very cold when operating so I may have over serviced earlier.

Out of curiosity, does this happen with the Fan switch in both High and Low positions?

Justin

 

[HoveringHMMWV]

Out of curiosity, does this happen with the Fan switch in both High and Low positions?

Justin

Yes. The fan position does not make a difference.

 

[justinn]

Yes. The fan position does not make a difference.

Do you have a set of gauges that you can record a brief video when it's happening?

RWH is on point. It sounds like the pressure switch is tripping the compressor/fan. Overfilled can produce similar symptoms to underfilled, so like autonomy pointed out, a set of gauges can at least point you in the right direction. Even a cheap set is better than no set at all. They are good to have in your tool box anyway

Justin

 

[thoner7]

If I remove the rear head unit from the backseat, just temporarily, do I risk ruining anything? As far as I can tell it’s two hoses and the power.

 

[Autonomy_Lost]

Well technically you are supposed to recover any remaining refrigerant before disconnecting any hoses.

 

[justinn]

And if it's already evacuated, then no, no risk. Careful with the drain line as the plastic it connects to can be rather brittle.