A/C is acting very strange

[Ray LeTourneau]

I plan on taking it to a dealer but maybe somebody has had the same issue with their A/C. This started a couple months ago and the reason I didn't get it looked at sooner is cause I though the problem went away.

When towing, my A/C does not work. Blows hot air no matter what I try. When not towing, it seems to work normally. First noticed this when moving from Clermont to Wauchula. Towing, no A/C. I checked every fuse I could find related to the a/c unit. No problems. I drove the truck to fuel up while in Wauchula and the a/c worked normally. I thought then that it was just a fluke...

Moved from Wauchula to Port Richey, same as before, no a/c while towing. I pulled into a Home Depot lot and disconnected the trailer pigtail, still no a/c. I raised the hood and the compressor is kicked in and running but the piping coming out of it was HOT! Arrived in Port Richey, parked, pulled the truck out and parked temporarily to set up. Moved the truck afterwards and the a/c was cold as ice. Checked again today, still good. What the heck could be going on???

I'll be talking to a local dealer but if anyone else has ever heard of anything like this I sure would be interested in hearing about it. Thanks!

 

[archbarb]

Probably a long shot, but it sorta sounds like a vacuum line problem!!!!!

Archie

 

[wdk450]

I'm guessing something intermittent associated with the bumps and jolts of towing. Vacuum lines, electrical, or even low freon??

 

[jnbhobe]

Ray; sounds like low freon 134. You could get a kit from wally world or a auto parts store and add some your self, and try that first for under $25.00. other than that maybe a vaceum pump

 

[Manzan]

I agree with Archie. Had a car with intermittent AC then none. Replaced a vacuum hose and all was well. Simple, low cost fix. Had a similar last September coming back from the SW. But this time it was a module that was not switching when it was supposed to. This was on my 2003 Suburban. Cost more than the vacuum hose but a whole lot less than a new AC.

 

[brianharrison]

I am not familiar with the Duramax set up but diesels don't pull manifold vacuum - not sure if much is driven off vacuum. I may be off base; but that's my thoughts.

Sorry, can't help at all with the problem.

Brian

 

[Speedy]

Ray,

From the things I have read on this issue (and I've had it happen to me twice) there are two things to try first before recharging. First is with the truck running and AC on pull the fuse for the AC and wait ten seconds then reinstall. Seems that the air control doors get out of calibration and cause air from the heater core to enter the cabin. Then all of a sudden they close when you turn the truck off. Second I would look into changing out the low pressure sensor on the AC system; there are a number TSB's regarding this sensor so that would be my next part to swap out.

I'll take a look at my AllData guide and see if they show where this sensor is. I haven't needed to dive into this fix yet since it's on 20 above right now.

 

[danemayer]

I don't know much on this subject, but I think the heat has to get exchanged somewhere - probably near where the water and transmission cooling also takes place. Have you checked your transmission temp while towing? Maybe you've got restricted airflow, or something else that's running hot, affecting the heat exchange.

 

[Willym]

I did a Google search and found something (not quite your symptoms, but similar) here.

http://townhall-talk.edmunds.com/direct/view/.f0f87de

Look down the thread to see an item on a 3500 AC problem, and a possible recall.

 

[jimtoo]

Ray,

I pretty much agree with Speedy. I also have an 04 like yours,,once on a while, very rare, mine will not cool, or maybe cool on the passenger side and heat on the driver side. Our units are all electric control. DO NOT try to add or recharge freon, nothing is wrong, it is not low. If it cools the freon is level is good. It is a program error with the control board and most likely not a fix unless you replace the A/C control. Next time it happens try removing the A/C fuse or restarting. The link Willym posted is a good link to look at, check post #341.

Jim M

 

[Ray LeTourneau]

Thanks for all the replies so far. I don't feel it's anything to do with low freon because when it works, it works great. I don't know about vacuum on the diesel but in the past, the system has done a few strange things like just shut down. It's the system that has separate driver passenger temp controls and generally I keep both sides set to 68 and on auto.
Speedy, I'll keep an eye out for your info on the location of that sensor. Is there a specific fuse for the a/c? I seem to remember seeing multiple fuses. Both in the cab and under the hood. I'll try tomorrow to figure out which is the main fuse and try that reset you mentioned to recalibrate.

I don't think it's related to any bouncing cause the thing rides better towing than when empty. Thanks again for all the help.

 

[Ray LeTourneau]

I don't know much on this subject, but I think the heat has to get exchanged somewhere - probably near where the water and transmission cooling also takes place. Have you checked your transmission temp while towing? Maybe you've got restricted airflow, or something else that's running hot, affecting the heat exchange.

Trans temp when towing is fine. Usually around 175. Coolant temp is normal as well assuming the factory gauges are correct. Voltage is a tad above 14. What ever happened to the days of carburetors and distributors? Vacuum advance and timing and dwell? I used to be able to rebuild a Holly 4 barrel in an hour or so.

 

[westxsrt10]

I know you are a real DIY- handy man. I'm surprised you don't have a manifold gauge set. First check your charge before adding 'Freon'. You will need the gauges and a thermometer. Temps/ pressure charts can be found online for your truck. Check the low and high side differantials at high idle. 900 rpm. (eg. 30psi low side, 180psi high side with low ambiant outside temp.)Its normal under high load for the AC to stop cooling via electrical in newer cars.

http://compare.ebay.com/like/360400452316?_lwgsi=y&ltyp=AllFixedPriceItemTypes&var=sbarYou may need adapters for the GM connections.Ray.... a Factory Service repair manual CD is a gold mine of information, I've downloaded them online for free sometimes.
A engine code reader (for diesels) for your under dash OBDII port may pinpoint the problem.

 

[Speedy]

What ever happened to the days of carburetors and distributors? Vacuum advance and timing and dwell? I used to be able to rebuild a Holly 4 barrel in an hour or so.

Ray,

Those days when away the day you bought a diesel (Duramax). The day I switched from carbs to fuel injection on my race car was a great day indeed. Same goes for the distributor; coil packs are the way to go.

 

[brianharrison]

Ray,
The day I switched from carbs to fuel injection on my race car was a great day indeed. Same goes for the distributor; coil packs are the way to go.

mmmmmm - race car - but that's another thread for another day; or on another forum.....

Take care,
Brian

 

[Ray LeTourneau]

A bit of an update. We took a ride to a Chev dealer today. Since we were both in the truck, Lin said her side was blowing cold. Mine was blowing Hot. I never did check her side before. The dealer said there are as many as 6 actuators that may need to be replaced and they have to determine which one (ones) are bad. Some are easy to access and others not so easy. After leaving the dealer the a/c was working normally. At least I know I'm not going nuts. They'll be checking into the smoking at idle problem too. They don't think the injectors are bad but related to needing a cleaning process they can do. We'll see what happens.

 

[Jcullipher]

Possible intermittent problem with blender actuator, the motor that sends heat or cool to individual sides of the vehicle. I know from experience that this can happen on gm vehicles with a/c systems like this, not a cheap or easy fix, one for a dealer. Hopefully, I am wrong and it is indeed something easy to repair.

 

[boatto5er]

Possible intermittent problem with blender actuator, the motor that sends heat or cool to individual sides of the vehicle. I know from experience that this can happen on gm vehicles with a/c systems like this, not a cheap or easy fix, one for a dealer. Hopefully, I am wrong and it is indeed something easy to repair.

Had a similar issue with our 08 Ford. We got heater in the summer sometimes instead of A/C! Dealer replaced the acuator (under warranty).

Shout out to Jimmy and Becky in DeWitt! I grew up in Pine Bluff, still have family there. Been through your neck of the woods many times.

 

[Bob&Patty]

Ray, 2 things could be wrong. 1 of the temp door actuators is probably bad. Its probably the one on top of the HVAC case under the upper dash pad on the right side. I replaced alot of them. A good tech can relace one in about 45 minutes. 2, if the cycling switch starts going bad, you will get an intermitent A/C compressor "no run" condition. BTW, there is NO VACUMN involved in a GM truck HVAC system. Its all electronic.

 

[Ray LeTourneau]

Ray, 2 things could be wrong. 1 of the temp door actuators is probably bad. Its probably the one on top of the HVAC case under the upper dash pad on the right side. I replaced alot of them. A good tech can relace one in about 45 minutes. 2, if the cycling switch starts going bad, you will get an intermitent A/C compressor "no run" condition. BTW, there is NO VACUMN involved in a GM truck HVAC system. Its all electronic.

Thanks Bob, the truck is at the dealer now. Hopefully their diagnosis is an honest one. I'd hate to pay for more than I actually need. The "Assistant" SM said there were several actuators and it could be one or more at fault. When she said more it made me feel there was the potential for them to charge me for more work that they actually do. All I can hope is that they are an honest service center.
Regarding the injector situation, she didn't feel there was any problem with them. Waiting for their call this afternoon.