AC compressor not engaging

[Grimace]

I have a 1999 Tahoe (dual air) that I was going to recharge the AC, but when I got everything hooked up, the compressor never came on. The clutch does move by hand (a little stiff) and I've checked the relays and fuses associated with the compressor. I'm going to test the clutch tomorrow, but my question is...would the clutch not engage if the freon level is too low? I didn't want to start filling it until the clutch engaged and the compressor was working...any thoughts or other troubleshooting ideas I can try? It's been over 100 for the last few days and we have a few more to go and I'd like to get some cold air blowing through my beast soon. Thanks in advance.

 

[Coveman]

yes the low pressure switch will prevent the ac clutch from engaging. When you put gages on it verify the level of charge, if its empty or nearly empty you should draw a vacuum on the system to see if it has any leaks before adding charge. The hi/lo fill valves are known to leak over time, plan on replacing those as well

 

[exp500]

This might help-

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

 

[Joseph Garcia]

^^^^^x2^^^^^

 

[BattleTank]

Compressor won't engage until it sees a minimum LOW side pressure..typically around 20-30 psi depending on mfr.

Get a good set of a/c gauges and check the pressures before filling. If its zero, look for a leak. Most of the time you can see oil at connections or crimps in the line.
And if it is zero, you will need to vac the system for at least 10 minutes, then let it sit for 5 minutes watching for a leak down. If no leak, proceed with filling with correct amount of freon.

Don't forget, its an EPA violation to vent freon into the atmosphere. If you have a nosy neighbor that is a stickler for reporting people, you don't want to get caught doing this.

 

[Grimace]

Checked compression and it was low, but not zero. Added some freon to bring it up a bit and compressor still doesn't kick in. I'm thinking I need to replace it.

 

[Eman85]

Does the compressor have power and ground when it doesn't "kick in"? No power and ground and no compressor will kick in. If you do have power and ground you might have a bad clutch which a new compressor would come with a clutch.