Automotive A/C experts inside please.

Billydroveit

Billydroveit

Club Member
2002 GMC Sierra 2500HD My AC has been degrading in performance. I don't drive it too much anymore so i've been a little slow to notice. It has 50 pounds solid on the low side while running, but the temp coming out of the vents is a joke. My guess till i get my thermo in there is about 60 to 65 at idle and maybe 55 while driving. The blend door is functioning. It seems the compressor is sensitive to shutting down while driving, specially away from a light. System has never been serviced. Could the filter be plugged? Any ideas?

Thank in advance.
 
whats the High side pressure? we HAVE to know this


if you dont have a manifold gauge set, I can hook up tomorrow or this weekend, I live in Taylor, work in melvindale
 
dave89iroc said:
whats the High side pressure? we HAVE to know this


if you dont have a manifold gauge set, I can hook up tomorrow or this weekend, I live in Taylor, work in melvindale
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Ya i figured hi side would help, but i don't have a manifold set. I'm leaving for vaca sunday. I can supply 12 of your favorite for some help, if that works? I'm at Northline and Tele.
 
1BADAIR said:
before you visit dave take a garden hose and wash the radiator and condensor out from the engine side towards the grille
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I've done that a few times when i wash the truck and once with a power washer when i bought the truck. It belonged to a construction company forman and was driven from site to site. It's a 2WD truck, and never sees any mud or off roading. Thanks for the suggestion though, most people overlook that.

It worked good last summer, but not as good as the summer befor. This winter it sat without being driven till basically the holiday weekend last month. I figured it was leaking but the low side pressure being high throws me to think the filter is plugged or something else is going on. I can do AC system work, but i've never had to diagnose much other than a pressure switch or bad clutch.

Dave, let me know when you have time. I'm around all day.
 
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On a day like today 50 psi low side and 50 to 60 degree outlet temp is about right. High side pressure is needed. If the clutch cycles off a lot the system may be low
 
Plugged orifice tube would cause a lower than normal low side pressure. High side reading is needed as said before. Cabin air filter clean?
 
Billydroveit said:
2002 GMC Sierra 2500HD My AC has been degrading in performance. I don't drive it too much anymore so i've been a little slow to notice. It has 50 pounds solid on the low side while running, but the temp coming out of the vents is a joke. My guess till i get my thermo in there is about 60 to 65 at idle and maybe 55 while driving. The blend door is functioning. It seems the compressor is sensitive to shutting down while driving, specially away from a light. System has never been serviced. Could the filter be plugged? Any ideas?

Thank in advance.
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Those systems tend to leak a bit of refrig over time so your probably just low on charge, does the compressor cycle on and off excessivly? If so just get a can or two from autozone. Also take a look at your fan clutch and make sure it is locking when the a/c is on that will make a huge difference and high pressures if there isnt any airflow across the condensor as well. Good luck and get that fixed! its too damn hot right now lol
 
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I would say those outlet temps are about right for the first 15 minutes, but after that they should start to drop. I wish I could monitor pressures while driving to see if its cycling because the pressure is too hi, or low. Sitting in the driveway bringing rpm up the low side stays at 50. If it was low on freon, wouldn't the low side pressure drop off in higher rpm's and cycle the compressor off because of low pressure?
 
Ok, found out my gauge is 10lbs off. Turns out the system was low and it was cycling off the low pressure switch. I added about 6oz. The vent temps were bouncing between 65 and 75 when i put my thermometer in. Now i get between 40 and 51 while cruising at 40mph. and the low side pressure at idle is 50-55 psi with an ambient of 93*, which should be fine.

2012-06-29_17-36-55_37.jpg


+1 to all who helped.
 
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