LBZ: A/c only works when it rains out help?????

[Nhill22189]

2007 2500hd LBZ 150k. I've been having problems with the ac compressor not engaging and running the system. I've put a lot of time in searching for the problem I've check pressure levels vacuumed the system out and recharged found no leaks. Checked all pressure switches fuses relays and ect. I've finally realized that the past 3 times it's rained the system works perfectly all the time until the truck sits and drys out. If anyone has had this problem and could point me in the right direction to maybe fix the problem it would be much appreciated.

Thanks.

 

[Bustedknuckles]

It might be over charged and the water across the condenser is dropping the pressure enough that it kicks on. Get some gauges on it and see what the high side pressure is.
Edit: i need to learn to read lol. Man idk, you got a weird issue for sure! It has to be a sensor of some sort. Maybe the cabin temp sensor or something? Got a scan tool that can read BCM info?

 

[WVRigrat05]

Mine was ass backwards but, Mine only worked if it was 100% dry out. Any fog or drizzle anything it quit working. Mine turned out to be the ambient air temp sensor (the one on the pass side front of the truck. They couldn't even figure it out with a tech 2, I stubbled across it repainting my bumper.

 

[Nhill22189]

I know the problem is weird. It took me weeks to figure out that it only worked when it rains outside and also it worked once when I when threw a car wash but stopped working after a little cruise and it dried up. The system is charge properly and you can jump the system and all works perfect. I've changed out switches. Which ambient sensor? In front of the radiotor? My truck shows the temp on the mirror and it always within 2 degrees. Changing yours helped you?

 

[WVRigrat05]

There is two sensors on the LLY, one is the outside temp for the mirror (the one behind the grill) and there is another one (ambient air temp) on the pass side of the rad. Support behind the bumper. My LMM has both behind the grille, I'm assuming with LBZ being a obs its still behind the bumper but I'm not sure one those. It fixed mine but mine only worked when dry not wet. Its a 30 dollar sensor.

 

[WVRigrat05]

I was thinking, find that sensor, spray it with water, if it starts working, change it, if not, go to the next sensor. Something is out of it map and the water is cooling it in a sense.

 

[Nhill22189]

So the other air temp sensor is on the passengers side behind bumper? How do I get to it?

 

[WVRigrat05]

Pull the grill and pass side park light. I'd just spray some water around the pass side park light and behind the pass side of the front bumper first. Save taking it all apart

 

[Nhill22189]

Okay so my ac stopped working after the rain stopped. I sprayed water around that area and nothing happened. I took some things off and found the sensor I touched it an then the compressor came of and went off couldn't make it happen again..... Is the other sensor the same the one in front of the grill? Could I swap them with each other to see if that works?

 

[Awenta]

Drench that sensor. It seems that's the problem if it worked when you touched it. Check the wiring too it. I don't know if jumping it will cause the sensor to bottom out or max out.

Or just change it out, verifying the wiring isn't damaged. Probably the cheapest part of the a/c system.

If they have the same part# on them then you can swap them.

Sent from my SM-N910V using Tapatalk

 

[Nhill22189]

Just tried soaking the sensor and got nothing. I'm going to wait till tomorrow and check the wiring futher. Are there anyways to check to see if the sensor is working properly? Or should I just replace it? Using a volt meter what should I be reading for volts when I see if power is being sent to it?

 

[WVRigrat05]

Not 100% sure on the voltage, I think they are 5 volt references but do not know for sure.

 

[Nhill22189]

What is the second sensor for? Does it allows the hvac system to recognize the temp and decided whether or not the compressor enages?

 

[Nhill22189]

I've been doing some research and a lot of forums are saying that the second sensor behind the passenger marker light is for the temp to be displayed on the hvac module. Mine is a manual set temp the sliding type mines not the automatic type. Does this make and difference?