A/C Compressor not engaging

[dangerous]

The A/C is not working - checked the compressor and it is not engaging. I cannot figure out how to troubleshoot. I bought 2 books and they talk of fuses or fusible links, but do not tell me where they are, how many there are and how to fix or troubleshoot.

It is a 99 Suburban 1500 with Dual air.

Appreciate any help.

[ewh442]

does it have freon in it? there is a switch on the side of the drier wiyh two wires, if you jump across the wire terminals it should enage. those switches are known to be bad, sometimes you can tap on it and the compressor will engage.

[dangerous]

Excellent - will try in the morning - wife has the burb.

[dangerous]

OK - new info. I bypassed the top switch on the accumulator and it allowed power to go to the compressor. The compressor stayed on and after I attempted to charge, LO was 25 and Hi 5.

I tried to bypass the lower switch on the accumulator aqnd ultimately realized that the upper switch must be the low pressure realy cutoff sawitch, because when the fren level (2.5 cans) finally got to LO45 and HI 180, I noticed that then switches (now NOT bypassed) where cycling the compressor off when the LO went below 25(?). Then tthe system would start building up pressure again and once it got higher, it would allow the compressor to come back on. Somewhere in this timeframe, I also turned on the read air, which seemed to cool fairly well. The front was baarely cool.

A note - when I was bypassing the upper relay switch, the line was freezing up at a simple connection fitting about 6" behnd the radiator, towards the firewall and on the passenger side. Once we got the 45/180 readings, and the switches were on their own, no freezing up ocurred.

At that point we figured that there must be some small leak somewhere, as we had 2.5 cans in, teh rear A/C was ok and teh front was semi cool. I figured that if it kept a charge for a few days, that later in the week, I would replace the accumulator and recharge.

BUT - when we disconnected the quick connect fittings from teh guages, BOTH schrader valves stayed open - I could not get them to shut. Maybe that is my leak! ?????

So today I plan on getting 2 new schrader valves and recharging. If it holds a few days, then I will replace the accumulator and recharge.

[ewh442]

good. i hate those valves, they always hang open. i should know this but is that a new or old body style? if it is the old vortec those compressors are known to leak where they are pressed together, around the seams. if you run your finger under it it'll be oily. they sometimes leak around the hub also.

[dangerous]

thanks - I replaced the 2 valves on top the compressor - now awaiting time to check it out later in week - will keep you posted