92 Q45 A/C Pressure Switch not kickin' Compressor?

[rrack]

K...about two years ago I completely reworked the A/C system because of some leaks...new drier o-rings, compressor, expansion valve, etc...everything has been fine until yesterday...Well, except for the darn cooling fan up front. That darn thing never really worked right. I sorta think it's the pressure switch for it that needs replaceing. This may be the time to take care of that too.

Anyway, I noticed that it just hasn't been cooling all that great when at idle...could have something to do with this Texas heat and not enough air moving up front with that fan not working. Anyway, I grabbed the gauges and a dusty can of R-12 from the vault. I couldn't get the gauges to work right...someone borrowed the fittings. I went ahead and used a small straight line and used the eye on the drier. It slowly took the entire can and the eye looked good. Appeared to be cooling great. Well, half way home today the compressor stopped pumping. Just hot air blowing. Once I got home I started tinkering and jumped the pressure switch on the drier and it will spin the compressor and cool fine. I'm not sure how this particular switch works. Will it shut down if over charged? I'm thinking it may just be clogged up? From what I'm seeing from the old drier, I can't simply swap out switches without evacuating the system of the R-12 gold. What to do? For the moment, I've got the pressure switch jumped for the short ride to and from work hoping I don't blow something up.

Any tips would be great.

Thanks much.Robert

[maxnix]

Good to see you back, RRack.

Get some gauges. I bet you've overcharged. Sight glass isn't nearly sensitive enough.
Modified by maxnix at 8:39 AM 8/17/2006

[Q451990]

The switch is actually a Dual Pressure Switch - so it will cause the system to drop out if the pressure is either too high, or too low. I agree with Brian, gauges are your next step...

Heath

[rrack]

...great to be back...you guys are always around to help me out.

It's been a long time since working on cars then alone A/C systems. I'm pretty sure you're right that I over charged it. I didn't know that the pressure switch worked for both low and high pressure. I'll get those fittings for the gauges and do some more tinkering.

As far as that front fan, is that another pressure switch attached to a line just above the drier? I hadn't looked at it yet. Does it have a needle valve so I can swap it out without evacuating? I figured that I might as well get that fan going while I'm at it. I know that when I had worked on it a couple years ago, the main fuse was blown for the fan because it was full of leaves. It worked for a little while after replacing the fuse. I've already tested the fan motor and it's all good.

thanks much...

Robert

[rrack]

Well, that was apparently it...overcharged. As far at the condensor fan, I'm not sure what I was thinking about another pressure switch. It must be the radiator temp sensor that's bad. That's will have to be looked at tomorrow.

[rrack]

k...Everything seems to be cooling fairly well even under this Texas triple digit heat. However, I still can't get that fan working. I jumped accross the second pressure switch and still nothing. Now I'm trying to track down the thermoswitch on the radiator. Where is it on a 92 Q? I can't find exactly where it should be in the manual...I'm gonna try jumping accross that n see what happens...
Modified by rrack at 2:38 PM 8/24/2006

[rrack]

Well, i think i found it...lower left side down by the lower hose...i jumped accross the plug and got the fan spinning. Cools everything down much better! both A/C and engine temp...I'm guessing one of two things, either the thermoswitch is bad or it's full of gunk being at the bottom of the radiator. I'll pull it out later when the thing cools down. I'll either find a replacement or maybe just leave the jumper. It all depends on how much the switch is...

[maxnix]

I bet the relay is cheaper than a burned out motor.

[OwnerCS]

Bringing back this thread. Any tips for jumpering the switch?

Is it just making a connection across the pins?

[Q451990]

Yes. Check out page HA-88 in the 1994 FSM for the pinouts.

If you're just trying to get the compressor to turn on, I would jump out the actual compressor relay for charging or testing. That eliminates all of the other "checkpoints" in the system.

Heath