playsdixie

One month before I take my 85 vette to the U>P> of Michigan, where use of air is unlikely, it takes a crap down here....always worked great, ice cold....today it went hot....had the freon checked, fully charged...before I try to read that section in my fsm, anybody have any quick trouble shooting checks??? guessing it may be a pressure switch, maybe a fuse, not a expert on a/c...just know clutch is not engaging....and it's already hot down here..(which explains why i'm going to the u.p.....more deer than cars up there...thanks for any input.

Cliff Harris

It could be a bad low pressure switch. You can unplug the connector and bridge across the connector contacts. If the compressor clutch engages (the engine does not have to be running but the ignition must be on and A/C selected on the HVAC control panel) then that's your problem. There is a Schrader valve behind the low pressure switch so you can just unscrew it and screw on a new one. This is the low pressure switch:

Lloyd Smale

don't get to excited. There will probably still be snow up here! Mine was acting up last summer and I charged it and it was working when I put it away but im not holding my breath that it still is and if not im not worrying about it this year.

playsdixie

thanks cliff, I'll give it a try....

Hopefully the snow will be gone when I get there, my wife's not a yooper and I was hoping to introduce her slowly to the boon docks.....

HlhnEast

Well I can tell ya that driving during the summer in NEFL sucks without a/c but after sweating all day long, the 20 min ride home aint no different. Hell my company truck doesnt have a/c either. One day I will get my car fixed and the company truck will never, by owner policy, have a/c. The trucks were ordered new with out it!

I feel for ya! Take yer butt up to some cooler temps and enjoy the summer! Have a safe trip.

8a8mfh

How was it determined that it was fully charged if the compressor is not engaging? Thats impossible.
If someone took a static reading the pressure might show ok but still be low.

playsdixie

a buddy runs local pro modified shop....he had set of guages...that's what he told me...not up on a/c...guess i'm going to be....

playsdixie

I bought a big 4x4 to tow it, and as a back up incase I can't get out before the snow...or get there before it's gone....

playsdixie

just did cliff's test...clutches did not engage when the low pressure switch was jumped....off to find a new one...

playsdixie

realized my brain fart before I left the house....clutch did not engage when jumped..so switch is probably good....will have to look else where...just read the two sections in the fsm, not much troubleshooting help....verified vacuum ok......fuse ok..... any other easy check?...may have to take it to a a/c guy...

antfarmer2

I would turn the air on high and add some freon as it get up the compressor will start kicking on once the line is beer can cold your good to go.......take the fill valve off put a bit of spit in there and look for bubbles if some repace the schrader valve it can be done without loosing freon or get a new good fitting cap

Robert Perkins

Did you check for voltage at the low pressure switch. If you have voltage then check voltage at the A/C compressor clutch, if you have voltage the clutch may be bad. If no voltage at clutch check wiring.

playsdixie

this sounds like a good idea...am I looking for 12 volts?....

VikingTrad3r

dixie check this thread. looks like 12v is what you want. Cliff has some comments in this thread that shoudl help.

https://www.corvetteforum.com/forums...ot-engage.html

playsdixie

got 12 v at the low pressure switch....there's a two wire plug on top the compressor..it's got tape on it....should I read 12v there or if one lead is hot, could I ground the other to see if the clutch engages?.....getting pretty technical for me.....had to get a liberal arts degree....

playsdixie

ok...12v at the low pressure switch, 12v at the compressor, vacuum is ok...clutch still doesn't engage.....any tips on my next step would be appreciated.....aside from taking it to a a/c guy....which will be coming I think....if I run 12 v from battery to compressor terminal and a good ground to the other, should the compressor come on?....does it matter which one is ground or 12 v???

8a8mfh

I'd run 12 volts straight to the compressor clutch. It's an electromagnet, pretty sure polarity doesn't matter but not sure.

Or test it with an ohm meter, resistance should be something. If it's infinate the clutch is electrically open.

playsdixie

I'll give it a shot in the morning....I sure appreciate the advice....I've restored this car from nothing, yet I still feel like I don't know crap about a c4, factory manual notwithstanding.....it's been an adventure....

Robert Perkins

With 12 volts at the conector for the clutch I think only one wire on a 1985. You should here the clutch engage the car does not even need to be running. Recap connect 12 volts from the battery to the one wire on the A/C compressor clutch you should here a click when it engages. If not the clutch is bad. You can also take a volt/ohmn meter and read the clutch resistance should be around 3 ohms the best I can remember.

playsdixie

it is a two wire plug on top of the compressor....