A/C problem when towing

UnderDawg · June 11, 2003

Three weeks ago I purchased a used 2001 GMC extended cab Z71 w/5.3L with 18,000 miles. Yesterday I was towing an unloaded single axle trailer. About ½ an hour into the trip, the A/C started blowing warm air. I had the cruise set on 70MPH with the engine RPM's right around 2,000. This was a very level road with the engine only downshifting once or twice to compensate a hill. I turned the A/C off and about 20 minutes later I turned it back on and it was cold again. On the way back, the trailer was loaded with a motorcycle and it did the same thing. Only it waited about 40 minutes to blow warm air. This trip was only a 65 mile trip and the driving time was about 1 hr and 15 mins. What could be the problem? Should I expect this when towing? The trailer can't weigh more than 500 pounds with a tongue weight of about 80 pounds (unloaded). I haven't noticed anything with the A/C before. But I have never traveled that far without a trailer, yet. Thank you in advance.

bassdog · June 11, 2003

Take it to the dealer and have it checked, you should still have some factroy warranty I would guess.

seadoons · June 11, 2003

No driving style should affect weather or not the A/C works. I pull a 20' boat and my A/C has no problem. Take it in and get it fixed. A 500 lb trailor is nothing - you can reach 500 lbs by just having 4 or 5 people in the cab.

greyghost03 · June 11, 2003

About a month ago I towed a 16' double axle trailer loaded to the gills with a tree that was cut down in my back yard. Had no problems with the AC. If the truck only has 18K miles, it's still under factory warranty ..........take it back and make the dealer fix it- sounds like something is wrong!

Good luck

SilveradoWV · June 11, 2003

I definately dont think its the weight that is effecting the AC because there isnt any weight actually. The trailer loaded shouldnt effect the AC. But if it only does it when pulling a trailer, the only thing I can think of is that your trailer being plugged in is doing something to the electrical system in your truck. That sounds impossible but there is no way just layin a trailer on the hitch makes your AC hot! That only leaves pluggin the trailer in to youre truck as the only other thing you do differently. Then again it could just be starting to run out of that refrigerant stuff, I think you can get a gauge at an auto parts store and check it. But if you still have some warranty left, let the dealer check it!

NOMNTX · June 11, 2003

Sounds like maybe a radiator fan clutch if its going bad it will not create enough head pressure for the ac.

The extra drag might be enough to pull it down.

Just my 2 cents

sjspor · June 11, 2003

Okay, so what would cause the AC to blow warm.. Forget about the trailer...for the most part.

1) low pressure cut out, if you system is low on R134-a, the low side pressure will be to low, and cut out, but it will come back as the soon as the switch closes again. This will show up as the compressor cycling on and off alot...

2)high pressure cut out, the hide side pressure gets to high, what could cause this is an overcharge, but again it would be more cyclic, not run for a while, and die for a while. A dirty condensor would be more suspect, is the coil clear and free of debris. Also, is there an after market tranny cooler in front of it??? This could be the trailer factor! Ah ha!

3)Moisture in the systems... IF there is moisture in the systems.. it may slowly freeze at the expansion valve, blocking the flow of liquid into the evaporator, this has to melt before the system will work again..

Just my 8.7 cents...Check the condensor and for an add on tranny cooler...

UnderDawg · June 11, 2003

***UPDATE***

I called my dealership and explained what happened. The service manager told me that it sounds as if the condensor froze up. I ran the A/C on recurculating air and he explained that once it reaches the temp. I like to turn in to outside air.

Does this aound right?

seadoons · June 11, 2003

I drive a lot of long trips. I drove a 6 hour trip from houston to Arkansas, and it was 90+ degrees outside. I had the A/C unit on re-circulating air the entire time, and there were no problems. No where in the manual does it say that you can't leave it on recirculating air all of the time. There is something wrong with your A/C.

sjspor · June 11, 2003

Underdawg... Just read your post, sounds like the dealer meant to say the Evaporator. And Yes it can freeze on recirc, but... It would have to be real cold inside the truck, and pretty cool outside to do this. Just like a window AC in your bedroom turned to artic death overnight, the coil will freeze.. as the low side pressure drops, the Freon will boil at a lower temp until the low pressure cuts out.

Shaners · June 11, 2003

There is a sensor somewhere in the truck that will shut off the AC when the engine is under extreme loads (like passing). I don't know if it is connected to the Throttle Position Sensor, or the Tach, or who knows what, but it could be faulty and could cause the A/C to shut down.

There is no-way that you were pulling a load heavy enough to cause a "normal" A/C override.

Torp · June 13, 2003

Dawg,

Same problem with my new 2003, 13k miles on it. I was not towing either. I have an appointment today at 2:00 pm with the service guy. I will let you know what they say. I checked the coil & evaporator on my truck, there was no external icing or anything. Not to mention is almost 100 degrees outside when it stopped working. I'm guessing some electronic gizmo that will stun the world needs a little tweaking. Chevy needs to put a usb cable on the truck so we can plug it in, get online and have the dadgum thing tested online.

Torp · June 16, 2003

Got my a/c serviced on Friday. Turns out my a/c problem was the compressor cycling switch on top of the engine. They are bad on all 2003 GM V-8 engines. The service manager told me that they are high fault items on GM trucks period.

MarkD · June 16, 2003

I had a similar problem on my Camaro. There was a $20 sensor telling the AC controller that the system was frozen up. So it would run the compressor for a while, then turn it off to "de-frost" the HVAC system.