M1152 A/C blowing hot

[Hmmv4me]

I have been working on this one for a while with little luck so figured I would jump in and post here. Pardon my ignorance, I am not great with A/C but I can usually get by.

My M1152 front A/C unit blows warm to hot. No rear A/C installed. It will cool down a bit when I first start up but as soon as I take a drive, it's gone. Ambient temp today was 99. Low side is at 50psi, high side is at 315psi (at idle). Both fans on the condenser are running. compressor is running. I thought it was the hot water valve but I clamped it off and no change.

Any thoughts?

 

[Pstyckiewicz]

This one might be a random fix. I just took my truck for a drive…..been fixing and painting it for some time. Went down the street and the cab filled with exhaust/smoke. Well upon further inspection I found that the vent/pipe that crosses over the engine was gone/ never there since I got it. So warm air circulating around the engine was now making its way into the vent and into my cab. A little duct tap solved that for now. In your case you could start to move and warm air could get forced into an open vent/hole.

 

[Hmmv4me]

This one might be a random fix. I just took my truck for a drive…..been fixing and painting it for some time. Went down the street and the cab filled with exhaust/smoke. Well upon further inspection I found that the vent/pipe that crosses over the engine was gone/ never there since I got it. So warm air circulating around the engine was now making its way into the vent and into my cab. A little duct tap solved that for now. In your case you could start to move and warm air could get forced into an open vent/hole.

Interesting thought. I know the crossover hose is missing. I'll see if plugging the hole solves the issue. Thanks.

 

[Retiredwarhorses]

50/315 is not correct…look at an ambient OAT to see what the LOW/HIGH should be.

 

[Mogman]

I have been working on this one for a while with little luck so figured I would jump in and post here. Pardon my ignorance, I am not great with A/C but I can usually get by.

My M1152 front A/C unit blows warm to hot. No rear A/C installed. It will cool down a bit when I first start up but as soon as I take a drive, it's gone. Ambient temp today was 99. Low side is at 50psi, high side is at 315psi (at idle). Both fans on the condenser are running. compressor is running. I thought it was the hot water valve but I clamped it off and no change.

Any thoughts?

Sorry, I see you addressed the water valve, are you sure you had it blocked?

 

[Hmmv4me]

50/315 is not correct…look at an ambient OAT to see what the LOW/HIGH should be.

It's probobaly over charged. I was just trying different pressures to see if it would make a difference. Started with 1.8lbs.

 

[Hmmv4me]

Sorry, I see you addressed the water valve, are you sure you had it blocked?

I have a clamp on the hose.

 

[Mogman]

It's probobaly over charged. I was just trying different pressures to see if it would make a difference. Started with 1.8lbs.

According to the chart I looked at for 134A those numbers would be about right for 100F but IIRC that would be with an engine speed of 1800-2000RPM not at idle.

 

[Hmmv4me]

According to the chart I looked at for 134A those numbers would be about right for 100F but IIRC that would be with an engine speed of 1800-2000RPM not at idle.

It actually drops at higher RPM's.

 

[Mogman]

Just for giggles touch the heater core (carefully) it is accessible on the left side of the evap between the evap and the tunnel and make sure it is not hot.
It should be making some cold air, the numbers are not that far off.
What are the numbers at around 1800 rpm?

 

[Hmmv4me]

Just for giggles touch the heater core (carefully) it is accessible on the left side of the evap between the evap and the tunnel and make sure it is not hot.
It should be making some cold air, the numbers are not that far off.
What are the numbers at around 1800 rpm?

So, I guess I just thought I had the hose clamped off. It was still letting some coolant through. changed my clamp and blocked off the missing crossover tube and it is now blowing cold. Self inflicted I suppose. Thanks.

 

[Pstyckiewicz]

Are you going to change the electric hot water valve? Or just clamp it off when it’s hot out. Kinda got the same problem with the hot water still heating up my heater core while the A/C is on.

Read somewhere that these valves don’t work that great and hot water still gets through. I contemplated putting an old mechanical style in and installing it on somewhere on the A/C data plate. Or getting a A/c On/off/ heat on switch and putting it where the A/c on off switch currently is and changing out the valve to somthing that would open only the toggle switch is on the heat on mode.