A/C Blowing Hot Air

tk_427

Original poster
Member
Mar 13, 2012
12
Omaha
Hello,
turned on the A/C today and the system would only blow hot air. I checked all fuses and they are all good. Opened up the hood and rolled down the windows, turned the a/c on and I can here a click and there is a drop in the engine idle. I jumped the low pressure switch and the I can hear the compressor running. None of the a/c lines are cold when a/c is on. I'm looking for some ideas that I might have not tried before I bite the bullet and take to a shop.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Jumping the low pressure switch, when you have a leak and the refrigerant has left the plumbing, is a very risky thing if you do it for more than a few seconds. Compressors hate to run dry. I strongly recommend getting it into a shop before trying another risky thing without knowing the downside.
 

tk_427

Original poster
Member
Mar 13, 2012
12
Omaha
I only jumped the switch for 3-4 seconds to see if the compressor came on, I am aware of the risks that come with bypassing the switch, but thanks for reminding me again. Funny thing is, when the switch is plugged in, I can hear the system turn on in the engine compartment when I push the a/c button. I thought that the a/c system wouldn't turn on at all if there wasn't enough of a charge of r134a? I guess that is why I am questioning other options that I might not have thought of to try before turning in over to a shop. Also, I did replace the fan clutch when I bought the vehicle. It was used and had about 50k on it when the fan clutch went out. I now have 140k. Could that be bad again?
 

MichEnvoyGuy

Member
Dec 3, 2011
523
Really, you need a set of gauges and the experience with automotive HVAC to truly diagnose it from this point.

It can get expensive by diagnosing the wrong way. I dont think jumping the low pressure switch for a few seconds damaged anything BUT if the compressor runs dry you can end up with not only a seized compressor (and yes, they are quite fickle), but a system full of compressor shrapnel which will only add to the repair bill.

Best bet: Get it to a qualified and experienced (reputable helps too) place to diagnose the A/C system.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
tk_427 said:
I only jumped the switch for 3-4 seconds to see if the compressor came on, I am aware of the risks that come with bypassing the switch,
Sorry if that came across the wrong way, but we have seen posts from members who think their low pressure switch has failed, and that jumping it is a proper fix. :redface: Now we know you're not THAT sort of goof, we know you won't do any more damage. A low pressure situation shouldn't even cycle on for a second, IIRC, but the best thing to do next is check pressures. Buy gauges if you want to be a bit more self-sufficient, but evacuating and recharging a system takes a lot more than gauges alone to do well, as you know. The fan clutch could be totally dead and the AC system should at least start up and get the receiver/drier chilly. It may not get rid of adequate heat to get the cabin cooled down at idle on a hot day, but the fan clutch isn't as vital a part of the system as you might think. At 140K, I bet you just have a leak.
 

tk_427

Original poster
Member
Mar 13, 2012
12
Omaha
Thank you for the info guys! I'm glad that I have now officially been labled "not that kind of goof" :smile: I have been a member of the Trailvoy forum for as long as I can remember and that as helped me save a lot of $$$ on repairs that I have been able to do myself. Now that I am a member of this forum, I hope my string of luck can continue! I will take it to an A/C shop and see what they can do for me. I will post with more info once I have the results.
 

tk_427

Original poster
Member
Mar 13, 2012
12
Omaha
I stumbled upon one of your posts that had the move to GMTNation or die text on it! :rotfl: I figured I better move or else. Glad I read that post, glad I am here, and hopefully I don't have to shell out too much to have cold A/C this summer. I do have to say, that anytime I have had a problem with the vehicle, your answers on the TV thread have always been the most help. I'm glad that I can always do something myself. I love my TB and as long as I can keep it running, I'm going to keep it.
 

tk_427

Original poster
Member
Mar 13, 2012
12
Omaha
**UPDATE**

I hooked up the gauges today and freon (R134a) is low. for now, I'm recharging and going to watch it to see how fast it leaks, because if it is low, it has a leak somewhere. Hopefully it won't leak very fast. Next issue. I have cold air blowing out on the passenger side, and not cold air blowing on the drivers side. Going to have to take it to a pro to do a proper test...nuts!
 

cody_s

Member
Dec 6, 2011
625
Atlanta, GA
tk_427 said:
**UPDATE**

I hooked up the gauges today and freon (R134a) is low. for now, I'm recharging and going to watch it to see how fast it leaks, because if it is low, it has a leak somewhere. Hopefully it won't leak very fast. Next issue. I have cold air blowing out on the passenger side, and not cold air blowing on the drivers side. Going to have to take it to a pro to do a proper test...nuts!

Best of luck to you, mines the other way around, drivers side blows cold air, and my passenger side blows hot air. I guess I'll have it looked at sometime soon. With the weather getting warm and all, it's going to be hell for anybody riding shotgun.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
I used to say that any passenger to driver's side imbalance was caused by temp actuators, but a few members have reported that incorrect AC charge could also cause an imbalance, as different parts of the AC evaporator have air flowing through them to the two sides. A manual HVAC control can't compensate for a temp gradient across the evaporator.

But mostly it's the actuators. Pull the dash trim and observe them try to operate.

allactuators-orig.jpg
 

tk_427

Original poster
Member
Mar 13, 2012
12
Omaha
Roadie, your correct, about the air imbalance due to a low charge. Once I had the a/c charged to the proper amount, I started to get cold air out of both driver and passenger side vents. My TB has held its charge for 4 days now. We have been driving around all weekend and it has been in the upper 70's lower 80's the past 3 days. I hooked up the pressure gauge up to the a/c system a few minutes ago, and it was at the same reading as it was when I charged it. I am still keeping an eye on it and once I have a little extra $$ to take to an a/c shop (re-roofing the house and knee surgery in the next month) I will have a full test done to see if there is a leak somewhere. Thanks for all of the help and I will keep everyone posted.
 

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