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View Full Version : A/C Troubleshooting


LanceW
07-23-2003, 15:20
Air Conditioner pooped out on me last night- I had been hearing some belt squeal recently and was getting ready to change the belts and tensioner, but everything was working until it stopped. No more squeal when I hit the a/c button, no cold air from the vents, no sign of a burning belt.

I haven't even looked under the hood yet, truck is out at the barn and it was raining cats and dogs when I got there. Fuse is ok.

Any suggestions on what to look for? Hoping for a hint that prevents having to take it to the shop.

Thanks in advance for your help. As hard as it was raining, may never get the truck out of that mudhole anyway.
HowieE
07-23-2003, 16:32
Lets look under the hood first. If the belt is still in place and tight try turning on the AC and see if the clutch comes in. If the clutch comes in and stays in you have gas in the system. Rev the engine up to about 1500 rpm and touch the larger pipe coming into the compressor. This pipe should be cold to the touch. If it is warm or hot you have a bad suction valve in the compressor. Do not touch the smaller pipe unless you want a good burn.
If the cluch did not come in you may be low on gas. If it went low on gas that quickly, working one day and not the next, I would look for a large leak.
patrick m.
07-23-2003, 17:46
Howie E nailed it, the only thing i can add, is if the system has not lost its refrigerant, check the low pressure switch on the accumulator.
charliepeterson
07-23-2003, 21:55
One more thing to look at. You can grab the A/C clutch with your hand and turn it. With no juice in the system the clutch turns easily. While turning try to pay attention to any hard spots. If it seems like the clutch gets a little harder to turn than other spots the compressor is toast, the pistons inside are worn out.
Too many people add refigerant without adding any oil first.
One last thing is if the clutch turns hard you have lots of refrigerant behind it and the low pressure switch on the filter/drier is usually the culprit. Unfortuneately I bet you lost the charge through a leak somewhere. Look for the oil stains!
LanceW
07-24-2003, 06:07
Many thanks, gentlemen- we'll start there.
catmandoo
07-24-2003, 07:15
this should have the serpentine belt if so and you say it was squealing before it quit. that should help narrow it down either the comp locked up and took out the clutch or maybe the pressure switch at the drier you can pull off the harness and jump across it and the comp should kick in.
David Brady
07-24-2003, 09:14
I've had to do two things on mine recently at about 145K, the pressure switch was sticking on the side of the dryer. The guy at the AC shop said to tap it if you couldn't see any reason why things weren't working. I didn't get to, they just replaced mine. I also replaced the idler pulley on my serpentine belt system, the bearing was starting to squeal. I hope this helps, those AC shops are busy this time of year.
StephenA
07-29-2003, 07:48
My belt also began squealing lately, and I replaced the tensioner (idler pully) and put on a cheap carquest serpentine belt, & it stopped squealing. The belt remained a bit out of range on the markings on the tensioner, so I ordered a new belt from Goodyear thru Pick Pro Parts at Yahoo (part# 4061010 for $18.57 vs. $41 from Goodyear Service Center and $67 from GM Dealer!!), which hasn't arrived yet, but should put things in range on the gauge.
The belt was jumping and making quite a lot of chatter noise before I put the carquest belt on along with the new tensioner, which did not seem to have a noticably stronger spring than the old one. Now it's quiet, but when the clutch is engaged, the belt vibrates up to 3/4" on each side of the A/C clutch pulley. I thought I'd rotate the clutch by hand and look for hard spots as Charlie suggested, to see if the pistons were starting to wear out... should this be done with the belt removed?
LanceW
07-29-2003, 08:32
believe it will spin for you as long as the clutch is disengaged.

When I finally got back to the truck on Friday, it was a CND (could not duplicate)... everything engaged and the a/c temp was great. Low-pressure switch turns out to only be 3 years old w/ 35k miles, so I suspect moisture from the lousy weather and a lot of sitting lately. Was actually happy to hear the belt squealing.

thanks again
LanceW
07-29-2003, 08:32
believe it will spin for you as long as the clutch is disengaged.

When I finally got back to the truck on Friday, it was a CND (could not duplicate)... everything engaged and the a/c temp was great. Low-pressure switch turns out to only be 3 years old w/ 35k miles, so I suspect moisture from the lousy weather and a lot of sitting lately. Was actually happy to hear the belt squealing.

thanks again
StephenA
07-29-2003, 10:01
It's been a record 100 to 107 degrees here in Colorado this month, so I glady put up with the squealing until the new belt & tensioner fixed it... I don't know if I even needed the tensioner.
Does your compressor rotate with any hard spots? I think these things draw about 8hp, so they are obviously doing some work, but I don't know if my belt vibrations are normal or an indication of a pump on the way out...
charliepeterson
07-29-2003, 21:51
With this new type of freeon the charge amount is critical. More is not better. I do alot of a/C work at home and at work so I never seem to find time for my truck. Last year my Evaporator was freezing up (frosted lines to the dryer tank). Two thing will cause this, low charge and air in the system. This spring I finally pulled the charge to fix it or see what was going on. Two small leaks and only a half charge. I pulled a long vacuum and put in a weighed charge and it's been running good all summer.
StephenA
07-30-2003, 19:37
Charlie - since you do a lot of A/C- can I ask you if it's normal for the belt to vibrate 1/2 to 3/4 inches on either side of the clutch when it's engaged? Thanks, Stephen
charliepeterson
07-30-2003, 19:59
No, I would say it's not normal to flex 3/4 inch. Yes, this compressor does draw power and the belt must be in good shape. When the clutch kicks out if the belt still flexes, even 1/4 inch, look real good at the tensioner and/or belt condition.
One more place to look at and everyone should look at this when ever your under the truck is the Torsion Damper at the crankshaft. If you ever see any kind of cracks or seperation pull this part off ASAP. This damper helps to keep the belt going in a straight line as well as keeping the Crank and Block from grenading themselves.
In the Member's Section here you will find a very good article on this story line. I believe this to be a 100,000 mile replaceable item.
catmandoo
07-30-2003, 20:35
charlies right belt flex should be at a minimum i recently went thru this on my gas suburban put in timing chain and water pump for trip to CA belt looked like it was do so went to o'reillys for new belt well about 400 miles later i finally turned on the a/c it lasted for about 5 minutes then heard little tinging noise and bad vibrsation kinda thought it was the road at first then nothing and i mean nothing no p/s idiot lites on temp climbin. pulled over and the belt popped off and in the process took 2 fan nuts loose that was the vibration anyway got to nearest town with gm dealer and got belt and nuts and when i went to put belt on i had to have the tensioner clear to the end of it's adjustment and it did'nt want to go on did more checking and it was right belt finally got it on and no more problems seems o'reillys gave me a belt just 1/2 inch too long.so watch what you get.
StephenA
08-02-2003, 21:32
New development: New goodyear belt runs smooth!

(I posted this as a new topic for those who need a belt.)

Recently, I installed a new Carquest serpentine belt and tensioner on my 6.5LTD only to find the tensioner gauge out of range and the belt vibrating almost an inch on either side of the A/C clutch when engaged. Before this, the old belt looked new, but jumped around the A/C compressor like a banshee under load. Upon spinning the compressor by hand, it rotated smoothly with out any hard spots.
Then I ordered a Goodyear belt (part# 4061010 -OEM for GM's $67.00 stock belt) for $18 from Pic Pro Parts at Yahoo and installed it and the tensioner gauge showed perfect alignment, and the belt ran smooth as silk with or without the A/C on. Lifetime warranty on belt from Goodyear, too! Now, it's the only belt for me.

Thanks, Stephen