808-3VZE

My 1994 V6 pickup i cant find that round relay for the ac compressor. The other day i noticed that my ac compressor clutch was not coming on when i hit the ac switch the light would come on but no power to the ac clutch so i go direct 12volts to the compressor and it turns on! So i decided to hook up a toggle switch with a inline fuse to engage the clutch direct to 12volts to get it to work so i hope you guys can help me out to find that relay!

millball

Are you sure that your system has enough refrigerant charge?? There are low pressure protections that may prevent compressor operation.

808-3VZE

yup checked it has the right amount of freon in it

wyoming9

iTrader: (1)

Did you also check if the pressure switch is working ??

So with all the safeties bypassed does your system blow cold air??

A copy of the EWD for your truck will help you trouble shoot things

As the compressor clutch is controlled by the AC amplifier after the assorted other conditions are met

808-3VZE

yes it blows cold. Where is pressure switch you talking about?

Jray215

Arw you looking for the location of the relay??? I have a 1992 and have had the same problems. The relay is behind the glove box. Im actually working on mine today.

scope103

That relay is only present on 4wd automatics (which is what 808- says he has). An extra temperature sensor in the water bypass cuts off the A/C when the ECT is too high.

Before I tore my dash apart looking for the relay on a fluke, I'd disconnect the temp sensor to see if that clears up the problem.

808-3VZE

I looked behind the glovebox and found the relay for the blower motor i was not able to find the other relay i was talking about. Hope you get yours fixed!!!

808-3VZE

My truck is a 5spd V6 so only the 4wd automatics have that round relay im talking about? The temp sensor you talking about is it the one for the gauge on the dashboard?

scope103

Sorry, I thought I saw "auto," You don't have the relay. The temp sensor is in addition to the ECT sensor and the gauge sensor (and you don't have that either).

808-3VZE

Thats good to know. Thank you. I'm wondering if a rat or a mouse has bitten one if the wires? I have it hooked up to a toggle switch so I good with that but if I can fix it like how it was I'm down for that also

scope103

That my be the worst resolution you could pick. The compressor isn't designed to run continuously. The Thermal Expansion valve allows refrigerant into the Cooling unit (Evaporator) "as needed" based on temperature. So the compressor cycles on and off based on the pressure behind the expansion valve.

Here's the basic circuit: http://web.archive.org/web/201102052.../2aircondi.pdf
Probably easiest is to make sure the "amplifier" is getting power when the switch is on. Then I'd try checking the pressure switch: http://web.archive.org/web/201102052...19pressure.pdf The pressure switch should be closed with engine-off, and when you force the compressor to run and bring up the pressure it should shut off.

808-3VZE

I shut the compressor off every 3 or 4 minutes. I don't let it run continuously i know it might freeze over! Thanks for the diagram I'll check those things