A/C stopped working, no power to Compressor

[jdjonesdr]

I recently replaced my alternator with a new OEM part. I went from 12V to 14 volts charging. Nothing to do with my new problem however other than I was experiencing low voltage.

Any way, I usually start my 94 full-size Blazer every few days to avoid draining the battery.

A few days ago when I started it, I noticed the A/C compressor stopped cycling after about 10 minutes. The A/C up to then was fine.

Everything else was functioning fine up to that point. We checked the gas and no problem there.

I checked the plug on compressor switch on the accumulator and they were fine - One is regular voltage and one is ground.

I unplugged the connector on the compressor and there is no 12 V there. No problem with the A/C fuse either.

What is between the accumulator switch and the compressor plug?

 

[movietvet]

Pressures? You keep saying no problem but do not supply pressure readings. How do you know pressure is good, like you said?

 

[jd33173]

Since you are saying you dont have voltage at the compressor clutch plug, its possible that the compressor switch at the accumulator might be turning the compressor off - which it does if you dont have enough freon in the system. if you dont have voltage at the compressor clutch, jump the compressor switch plug (TEMPORARILY) and see if the compressor kicks on. If it does, problem is either a bad compressor switch or you dont have enough gas in the system and the switch is cutting out to prevent your compressor from grenading over time. you may have a small refrigerant leak (my fave) that is causing the problem - look for dirty grease at the various hoses & connections to continue the investigation. if your compressor does not kick on after jumping the switch, you can try applying 12 v directly to the compressor plug and see if it kicks on that way - if it does not, you may have a bad compressor clutch coil.

 

[jdjonesdr]

Pressures? You keep saying no problem but do not supply pressure readings. How do you know pressure is good, like you said?

My a/c guy came over to check it.

BTW, love your truck.

 

[jdjonesdr]

Since you are saying you dont have voltage at the compressor clutch plug, its possible that the compressor switch at the accumulator might be turning the compressor off - which it does if you dont have enough freon in the system. if you dont have voltage at the compressor clutch, jump the compressor switch plug (TEMPORARILY) and see if the compressor kicks on. If it does, problem is either a bad compressor switch or you dont have enough gas in the system and the switch is cutting out to prevent your compressor from grenading over time. you may have a small refrigerant leak (my fave) that is causing the problem - look for dirty grease at the various hoses & connections to continue the investigation. if your compressor does not kick on after jumping the switch, you can try applying 12 v directly to the compressor plug and see if it kicks on that way - if it does not, you may have a bad compressor clutch coil.

My A/C guy feels it's probably the compressor relay in the cabin. Everything has checked out fine except for the lack of voltage at the compressor plug.

Everything is almost new. Accumulator, hoses, condensor, High pressure switch, compressor, etc, etc.

That voltage comes from the relay, so we're going to dig into the dash today.

I think that relay is behind the glove box or the center hole where the equalizer lives. I have a manual but it's not clear where.

 

[xXxPARAGONxXx]

Pretty sure AC relay will be underhood fusebox.

 

[jdjonesdr]

Pretty sure AC relay will be underhood fusebox.

Thanks! Mine is a '94 so no underhood fusebox

 

[PlayingWithTBI]

Mine is a '94 so no underhood fusebox

Look on the firewall next to the power distribution block. You may have 2 relays, 1 for the fuel pump and 1 for the A/C compressor.

 

[jdjonesdr]

Look on the firewall next to the power distribution block. You may have 2 relays, 1 for the fuel pump and 1 for the A/C compressor.

Hoo boy, we pulled that cover before and didn't even think about the relay that was in there. LOL. Wouldn't that be a kicker?

 

[movietvet]

Yes, I recently worked on a 94 K1500, over the summer, and his A/C relay was under that cover in the box. His problem turned out to be the female connectors were loose and not making good contact with the relay. I had a new relay just in case, I keep a couple popular relays in my tool box, but when I twisted the relay, while plugged in, the compressor kicked on and cooled. I pulled the box and pulled the connectors from the bottom and tensioned and reinstalled and plugged in relay and problem was solved. No new relay needed.

In the case I came across, and possibly yours, just replacing relays would not fix it. It is best to always do at least the basics of diagnosis/inspections before shooting the parts cannon at the problem. Unless of course you are a thousandaire, like me.