Hot AC on 01 Suburban

[93SHOcarguy]

I have plenty of freeon according to the gauges. We have checked with dye and find no leaks but when I turn on the AC all I get is hot air in the front and the back. I have checked all fuses that seem to be related to HVAC in the truck and all are good. Compressor does not seem to be kicking in at all. Where do I start?

I had a 95 Chevy truck that did the same thing and we replaced the low pressure switch to resolve the issue.

[leprams]

you have 2 issues first a/c clutch does it engage?and also check the blend door motors do the move the flap in the heater box

[Cusser]

Originally Posted by 93SHOcarguy

I have plenty of freeon according to the gauges. We have checked with dye and find no leaks.

Famous last words (you don't even have "freon" in a 2001, you have R134a).

Post both high and low pressures at 2000 rpm.

And jump with 12 volts positive (for just 2 seconds) the compressor "hot" lead and post whether it engages.

And while that compressor is unplugged, read its ohms resisitence and post.

[procaddytech]

In the underhood fuse block check the 10A A/C fuse and the 10A IGN E fuse. If either is blown, replace it and if it blows right away, there is a dead short somwhere. If the A/C fuse is blown, and does not blow until the A/C is operated for a while the compressor cluth coil is most likely shorting. If they are good try tapping on the A/C compressor clutch relay, or put your finger on it and feel if it is clicking while someone turns the A/C on and off. The PCM needs to see a request from the control head to ground the relay. The request goes through the A/C high pressure switch in the back of the compressor that must be closed to get to the PCM. There is also another high pressure switch in the discharge hose assembly that must be open. Then, of course there is the low pressure switch that must be closed. Schem: http://i36.photobucket.com/albums/e5...SuburbanAC.gif

[j cAT]

Originally Posted by 93SHOcarguy

I have plenty of freeon according to the gauges. We have checked with dye and find no leaks but when I turn on the AC all I get is hot air in the front and the back. I have checked all fuses that seem to be related to HVAC in the truck and all are good. Compressor does not seem to be kicking in at all. Where do I start?

I had a 95 Chevy truck that did the same thing and we replaced the low pressure switch to resolve the issue.

you must post the operating pressures low and high side...with the low pressure side above 5psi area the low pressure cutout switch should be closed..jump out this switch and see if it gets the compressor clutch to engage.. post back what you found.


with the guages connected and the compressor does not engage you cannot say it is fully charged ! with the compressor pumping then you can get the high /low pressures with the air temp environment to determine the refrigerent charge of the system...as well as any other component operating issues..

all you can be sure of is at this point you have pressure in the system ...this could be just a few ounces...

[Gustheiceman]

I had something similar earlier this year, turned out to be me being a "plonker= jerk" not realising that if the outside temperature is lower than 9 degrees the compressor will not kick in. If this is not the case, then maybe the sensor which measures the outside temp' could be faulty.
Gus in the UK

[j cAT]

Originally Posted by Gustheiceman

I had something similar earlier this year, turned out to be me being a "plonker= jerk" not realising that if the outside temperature is lower than 9 degrees the compressor will not kick in. If this is not the case, then maybe the sensor which measures the outside temp' could be faulty.
Gus in the UK

you must be talking 9 degrees C ...

if this were 9deg f I'm thinking more heat ...

at 9 deg c or about 45 deg f the compressor will short cycle in a hot engine compartment, at idle..