Mechanics and Wannabe Mechanics, I need your help.

[Bigscrb15]

I have a 2002 Chevy truck with 6.0L gas engine. Lately the a/c won't blow cold while idling and I can feel the compressor kicking on and off. While I am driving around or just sitting there pressing the gas at hold it around 1500rpm the a/c blows ice cold. Is this just the clutch or the entire compressor? It is not easy to get to the compressor but I think I can replace it if thats the problem. Will the pulley and clutch be 1 unit like my old Isuzu Trooper was? How hard is it to replace? thanks for the help.

[gery350]

if the rpm is set too low the computer will turn off the compressor to remove the load. if you idle up a little and notice the compressor not cycling the the rpm is too low.
if this were the case though the computer would raise it via the idle air control motor(unless of course the IAC motor is bad. is the check engine light on?

if it continues to cycle at a higher rpm then your freon level is too low.

its not a problem with the compressor, its a problem with the ac clutch kicking  on/off.

[Bigscrb15]

It does idle pretty low(500-750rpm) is this normal? is there an easy way to idle it up? This is my first fuel injected truck that had something go wrong, I have always worked on carbs.

[apkkfx400]

It sounds like the a/c system has a low freon charge.  The a/c is cooling when you bring up the rpm's because the high and low pressures are raising above where the low cycle pressure switch is cutting off the compressor.  This is a guess-a/c gauges need to be hooked up to diagnose properly though.

Mark

[bluesman]

OOOOOOO    OOOOOOOOOOO I KNOW THIS ONE!!!!!!
DID ANY ONE CHECK BUL OR PI??? CALL ME ILL TELL YOU HOW TO FIX IT
  561 966 0006   SCOTT

[apkkfx400]

As far as your idling concern-if your rpm's fluctuate erraticly at idle, you need to clean out your throttle body-you will not only correct the erratic idle but also maybe correct a sticky throttle body/accelerator pedal!

[gery350]

It sounds like the a/c system has a low freon charge.  The a/c is cooling when you bring up the rpm's because the high and low pressures are raising above where the low cycle pressure switch is cutting off the compressor.  This is a guess-a/c gauges need to be hooked up to diagnose properly though.

Mark

not to contradict but when you raise the rpm the lowside goes lower and the high side goes higher. the more rpm the compressor turns the more suction it creates(low side drops) and the more pressure it puts out(high side goes up)

the compressor is basicy a pump the faster it turns the more it sucks and the more it puts out. hence if it were low in freon it would cycle quicker at ahigher rpm because the low side would be lower.

[Bigscrb15]

so should I goto Autozone and get one of those recharging kits or should I try to idle it higher than 500-750rpm?

[gery350]

careful witht hte charging kits.
if you overcharge the system you can kiss your compressor goodbye.
i.e- the compressor is designed to work from lets say 200-250psi(output/ighside) if its full and you put a strain on the compressor by overcharging it you will fry the compressor.

so be careful with charging the system without monitoring the pressure.

i would try the rpm increase. that wont hurt anything. if it doesnt do the trick, just turn it down again.

but thats just my opinion.

[bluesman]

do you have a throttle cable on your truck?? or is it fly by wire??

[Bigscrb15]

careful witht hte charging kits.
if you overcharge the system you can kiss your compressor goodbye.
i.e- the compressor is designed to work from lets say 200-250psi(output/ighside) if its full and you put a strain on the compressor by overcharging it you will fry the compressor.

so be careful with charging the system without monitoring the pressure.

i would try the rpm increase. that wont hurt anything. if it doesnt do the trick, just turn it down again.

but thats just my opinion.

is there a screw on the throttle body to adjust it?

[apkkfx400]

It sounds like the a/c system has a low freon charge.  The a/c is cooling when you bring up the rpm's because the high and low pressures are raising above where the low cycle pressure switch is cutting off the compressor.  This is a guess-a/c gauges need to be hooked up to diagnose properly though.

Mark

not to contradict but when you raise the rpm the lowside goes lower and the high side goes higher. the more rpm the compressor turns the more suction it creates(low side drops) and the more pressure it puts out(high side goes up)

the compressor is basicy a pump the faster it turns the more it sucks and the more it puts out. hence if it were low in freon it would cycle quicker at ahigher rpm because the low side would be lower.

Ok-the pressures change-but the a/c compressor usually does engage for a longer period of time and doesn't cycle as rapidly as it does at idle.

Mark

[gery350]

have someone inside hit the gas pedal so you can see where the throttle rest on the throttle body. it should rest up against a screw. the only problem is the screw  may be behind a metal plug. you can try bending the tab that res against the screw(slightly and carefully) or remove the metal cap to adjust. it should be a torx head screw. just be careful dont hit it to hard.

[Bigscrb15]

alrighty, ill give that a shot. thanks for the help everyone. now I think about it when I am at idle, the trucks starts shaking every now and then because it idles so low, I have just never fixed it. if this doesnt work I will try to recharge it, thanks for the heads up on overcharging it, ill let yall know if it works tonight.

[bluesman]

ok this is the fix from the gm enginers
document id 1527156
with etc    < electronic throttle control>
  

 throttle body cokeing
do not bend or try to adjust anything!!!!
pull off intake hose while car off open throttle plate
and spray cleaner into and wipe clean with clean rag
you will see and feel a ridge where the plate hits the side of bore
clean off all debris.put back together and start truck and let ide
it will hickup and spit and sputter and finally will smooth out
check eng light may come on but after you cycle key cple times will go off
may say reduced power for cple min but will clear up also



there is a reprogram that we do also here at the dealer
but this will work fine also if you need the document ill try to email it to you???
simple fix  

[Bigscrb15]

I adjusted that screw that gery said and there was no tab in the way. It was very easy to do and seems to have solved the problem. It did not cycle at all for the couple minutes I let it run and blew cold air constantly. I didn't tighten it much but the truck just seems to run smoother now.