[Windfall]

I have a 93 with AC. I had a leak in the system I repaired it and then once I it was able to charge the system it holds the charge fine it runs well at first producing cold air. And after the engine warms up a little bit the AC kicks off. I thought it might be the relay I verified the relay is working but the PCM is cutting the ground off to that relay which stops it from working and I have no idea why the PCM is making that decision. Anything you can do to help me out as much appreciated

 

[dirtbag]

I believe over charge or under charge will cut the relay. Next step is to track down the pressure switch and see how its reacting.

 

[2001GTS]

Are you sure the pcm is cutting it off or does it just start blowing hot?

If it’s pcm then it’s as dirt bag suggested.
However there is a vac mod which helps, basically'install a check valve in one of the vac lines fixes a flapper door issue

 

[Windfall]

I believe over charge or under charge will cut the relay. Next step is to track down the pressure switch and see how its reacting.

I have one pressure sensor and it's a low pressure sensor. before the engine gets up and going the circuit is closed and after it does a cut off the circuit is still closed. If there's more sensors that I can't find in my diagram I would appreciate that That's probably where it's coming from.

 

[Windfall]

Are you sure the pcm is cutting it off or does it just start blowing hot?

If it’s pcm then it’s as dirt bag suggested.
However there is a vac mod which helps, basically'install a check valve in one of the vac lines fixes a flapper door issue

I have power all the way up to the control relay but the blue orange wire that runs to the PCM isn't supplying a ground. So it appears to me that the PCM is kicking off the AC for whatever reason.

 

[85vett]

If the AC compressor is turning off and staying off, but only after the vehicle is running and has gotten hot, my gut is telling me it's most likely overcharged. Do you have proper AC gauges or did you do it with an Autozone type can with a gauge built into the can? If so, what are the static (at ambient temp) pressures Hi/Low and what is the ambient temp? What are the pressures Hi/Low when the car is cold and the compressor is active. When you filled it (sounds like vacuum was pulled from what you said) how many ounces did you put into the system?

What 2001GTS is talking about is when the AC is working fine and you go to a situation to where the engine is not in a vacuum state (under acceleration) the AC will temp cut off until vacuum is restored.

 

[Windfall]

If the AC compressor is turning off and staying off, but only after the vehicle is running and has gotten hot, my gut is telling me it's most likely overcharged. Do you have proper AC gauges or did you do it with an Autozone type can with a gauge built into the can? If so, what are the static (at ambient temp) pressures Hi/Low and what is the ambient temp? What are the pressures Hi/Low when the car is cold and the compressor is active. When you filled it (sounds like vacuum was pulled from what you said) how many ounces did you put into the system?

What 2001GTS is talking about is when the AC is working fine and you go to a situation to where the engine is not in a vacuum state (under acceleration) the AC will temp cut off until vacuum is restored.

If the only problem is that that it was overcharged that would be great. I don't have proper adapters for my gauges I've ordered them. If the system is overcharged how would the PCM know to cut off the power to the a/c clutch relay?

I did purge the system once and ran it with a half charge of 10oz it was still acting the same.

Thanks for putting in the time to help me out

 

[85vett]

The system will turn off if the pressure is to high or is to low. Generally when it's too low it will cycle on and off though so you may have something else going on too. I've never done work on the Viper AC system but have worked on dozen's of other cars. You generally have pressure switches that will tell the computer if things are to high or low. If they are triggered the system shuts off to protect itself. It's possible its one of those. Sounds like you've found the sensor though already. It's possible it's bad as well.

The heat aspect is what makes me think charging issue. Freon pressure goes up with heat so if it was borderline at the start it will be to high and thing will shut down. But when you say you ran it with only 10oz in the system and it still did that, that starts to make me think I'm wrong as it wouldn't do that at that low of a charge. Worst case it should cycle.

Looking at the schematics, maybe check on the AC thermostat. Item 10 here. I'm not familiar with them so can't advise on how they interact with the system but if it makes adjustments based off temp readings it could be faulty and causing things to shut down.

 

[Windfall]

The system will turn off if the pressure is to high or is to low. Generally when it's too low it will cycle on and off though so you may have something else going on too. I've never done work on the Viper AC system but have worked on dozen's of other cars. You generally have pressure switches that will tell the computer if things are to high or low. If they are triggered the system shuts off to protect itself. It's possible its one of those. Sounds like you've found the sensor though already. It's possible it's bad as well.

The heat aspect is what makes me think charging issue. Freon pressure goes up with heat so if it was borderline at the start it will be to high and thing will shut down. But when you say you ran it with only 10oz in the system and it still did that, that starts to make me think I'm wrong as it wouldn't do that at that low of a charge. Worst case it should cycle.

Looking at the schematics, maybe check on the AC thermostat. Item 10 here. I'm not familiar with them so can't advise on how they interact with the system but if it makes adjustments based off temp readings it could be faulty and causing things to shut down.

View attachment 153191

That makes sense. I have to look pretty hard in my shop manual and see if I can find that control temperature sensor. I haven't been able to find it yet

 

[HughJass]

Disconnect the low pressure switch connector and install a jumper wire between sockets on the connector. Start the vehicle and request max ac. Does the ac continuous run now?

 

[99RT10&GTS]

^^^This^^^

 

[Windfall]

Disconnect the low pressure switch connector and install a jumper wire between sockets on the connector. Start the vehicle and request max ac. Does the ac continuous run now?

Problem resolved!
It was the coolant temperature sensor!
There's two coolant temperature sensors One of them for your gauge and one of them for the computer. One for my gauge was working just fine. But I did notice every time I started the car all the fans would turn on even when the car was cold. And so when the car would warm up a little bit it would go into an overheat mode and the PCM would cut off any exterior auxiliary components like the AC. I was probably running super rich too in that safety probably like a limp mode. But I replaced that temperature sensor on the water pump and it fixed all the problems.

Unfortunately we did lose a man sock it 13 mm you will be missed he is MIA.⚰

 

[GTS Dean]

Stay strong - all is not lost. At least you still have Sergeant 10mm.