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Old 06-25-2002, 02:11 AM   #1
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1984 31' Excella
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Yukon AC cuts out towing....

I am experiencing the cutting out of the AC on my Yukon 2 dr 4x4 when towing.

I recently purchased a 1984 31' Excella in perfect shape...On the first outing, I traveled about 20 miles and the AC of the Yukon stopped functioning. So, I called the local mechanic and returned to home for a looksee at the AC.

He found nothing wrong with the unit, so we disconnected the trailer plug, and battery of the Yukon to reset the computer, and then plugged everything back up, and it all worked and I restarted my trip...and about 22 miles into the drive, the AC light once again began flashing on the dash. I preformed the previous proceedure on the roadside and resumed the trip and 20 miles down the road it did it again....this is VERY annoying.

The Yukon has 3.42 gears, a large aftermarket tranny cooler mounted in front of the AC condensor, and it has the heavy duty radiator, a new 350 motor and rebuild on the tranny...and is running at about 190 on the temp guage, and yet, if I push it over 2500 rpms, the AC cuts out after about 20 miles. If I run under 2500 rpms, then the AC does not cut out.

The question is, does anyone have a reasonable explanation why the AC will not stay operating if the tow vehicle is operating at over 2500 rpms??? even if the motor coolant temp is under 210, and the tranny temp is not high enough to foam it up and blow it out the overflow???

Someone suggested that there might be a situation where the trailer is hunting ground in the wiring of the truck, because if I turn the Univolt switch to the battery off and run under 2500 rpms then I can go and tow with the AC on.

If anyone has suggestions, I would be most grateful...thanks!
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Old 06-25-2002, 06:15 AM   #2
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A/C problem

Welcome to the forum~
I agree with you that, this has gotta be the nuttiest problem I've ever heard of.
Trying to remember where I heard or read of something like this before. I'll give you what I can recall. It had something to do with a jumper wire in the glovebox and, this poof the computer into behaving..it too early in the morning for me..lol
Just curious, at what speed are you towing the trailer?(normal range should be 50 to 55mph) I know this sounds slow but, you have a lot of dynamics going down the road plus, at the slower speeds you don't shake up things in the A/S quite so much. like flexing, etc.
Keep us all informed on what your outcome is..
ciao
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Old 06-25-2002, 11:01 AM   #3
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Wow, that is a goofy and big time annoying problem.
If you haven't already, check in the owners manual and see what else shares the circuit breaker with the AC. We had a '95 Grand Cherokee that we used for a tow vehicle for a couple of years. When we first got it, the AC would blow a fuse once in a while and quit but only when towing. Without the trailer it worked fine. The dealer tried several times to find the problems with no luck. Turns out the back-up lights for the trailer were wired incorrectly The back up light circuit in the Jeep shared a fuse with the AC. Any time we put the Jeep in reverse, with the AC on and the trailer connected, it would blow a fuse.

Good luck,
Lee
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Old 06-26-2002, 07:51 AM   #4
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When the A/C quits working does the fan shut down? or is it still blowing but not getting any cold air? Have you turned the system off and continued driving and restart the A/C after a few minutes does the A/C restart? Does this ever happen with out the trailer?

You could have several different issues causing the problem, and may need to have an A/C service person connect gages to the vehicle and tow the trailer down the road until this happens.
Possible problems are 1. Evaporator core freeze up from high RPM operation. 2. Defective high pressure shut down switch. 3. It sounds as if the A/C is controlled by the engine controller and if this is the case any of the sensors in the A/C system which are defective could be causing the problem.
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Old 06-26-2002, 09:34 AM   #5
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AC Cutout

I had a kind of similar situation on my old S-10 when towing my Scamp 5th-wheel. In my case, it happened only at higher altitudes, never here in central Texas. I had it happen in New Mexico, Colorado, and at higher altitudes in Big Bend.

In the S-10, the vacuum would apparently get so low when pulling hard at high altitudes that the flapper doors that direct the airflow would all close off with a thump. I wouldn't have air from any vent in the truck, yet the AC compressor was still working. Once in the closed-off mode, it would tend to stay that way till a signifigant downhill came along.

When I would get a good downhill, the vacuum would come up enough that the flappers would pop open with a thump. Then, the succeeding uphill would close them again.

I just learned to live with it.
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Old 07-04-2002, 03:16 AM   #6
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Thanks to all for your replies.
I think the most likely is what Apple 1 said.
The fan does not shut down...the compressor does, and therefore there is only vent temp air.The AC light symbol on the panel goes into a flashing mode and the battery cable has to be removed from the battery and the trailer unplugged to reset the computer for the compressor to come back on.
It has to be
1)core freeze up from high RPM operation, but I hardly think 3000 is high RPMS..although I have had it quit on me at high altitudes before (Durango Colo)as Pahaska mentioned...
2)Defective high pressure shut down switch or,
3)Engine controller sensors for the AC.
There is no vaccuum flapping of doors or anything like that.
Perhaps the hints given will get me on the way to finding the solution.
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Old 07-08-2002, 09:27 PM   #7
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Is your Yukon capable of towing a 31 footer? My 99 Tahoe handles my 24ft TradeWind okay but I would not want to push it that far.

What does your owners manual say?

Take Care
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Old 07-08-2002, 10:08 PM   #8
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I am aware tha GM has limits set in the computer to stop certain things from exceeding a manufacturers threshold. Case in point I have a frend who's mom has a suburban. It runs stong up to 99 miles per hour, and at 99.9 miles per hour the engine shuts down until speed drops below 98MPH. I did not experience this but I would not lend him one of my cars! So this could be a factory program setting. You may want to check with some of the guys that do modified chips to see if this is one of the limits that GM set. Most of the chips adress horsepower and timing advance, but with the new intergrated engine management who knows? In many computers this chip is replaceable. If you replace the factory chip be sure the new one will not void your warranty.
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Old 07-09-2002, 03:10 AM   #9
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The towing capacity of my 1992 Yukon 4x4 with 3.42 gears and 350 motor is 7100 lbs.
According to Airstream's factory website, the 1984 Excella 31 trailer I have is dry weight at 5650 lbs....and it is certified wet weight on grain elevator scales at approx 6300 lbs. I don't see any problems towing the trailer except that I can't take Raton Pass on I-25 at 70 mph like I could if I had it behind a Power Stroke Diesel.
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Old 07-09-2002, 08:38 PM   #10
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This is the opposite street side view.
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Old 07-27-2002, 12:01 PM   #11
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Problem Solved!!!

Problem with the AC is solved.
It quit the other day while in a huge hurry due to being late for a concert. I was driving about 90 down some backroads in West Texas and the AC quits..no time to stop and reset it by removing the battery cable so I press on and make the gig on time.
I take the Yukon to the mechanic the next morning telling him it is doing it now...he had not been able to diagnose it up to this point.
The problem...a cycling switch that was in the process of going bad. Was over heating and not letting the compressor work long enough....and when under stress of higher RPMs and so forth would just load limit out and kill the AC.
New switch was $107.95 total bill installed and AC now produces 32 degree air from vents in the high, recirculate position which is wonderful considering yesterday was 102 in Lubbock, TX when I towed my Airstream back from Bluegrass Camp at South Plains College in Levelland, TX. And I had no problems at all generating 2800 rpms and 65 mph with no overheating despite the severe clear and 102 outside.
Thanks for all your suggestions....they did help.
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