hockey88fan

I've got a '92 pickup 3vze that the a/c has never worked for me, had the truck for 2 years. When I push the a/c button on the dash nothing happens. Any hints on where to start the troubleshoot? Thanks!

Bigal74848

Need a little more info. When you engage the a/c button does the light come on? Depending on what you have for a pressure sensor you may be able to jump it to see if the A/C compressor comes on ( two wire). I would begin by making sure that when the a/c button is engaged it lights up then move to the engine compartment and check to make sure the fuse isn't blown. More then likely you are low on R12/134. Please provide a little more info. tks
Bigal

Co_94_PU

iTrader: (-1)

FSM Ac sections, and troubleshooting

Start with the sight gauge, it won't activate unless it has "magic goo". Then the switch. And the AC clutch and compressor

All that aside, the first thing I'd really check is that it had a belt thats usually the first thing to go.

hockey88fan

When I engage the button the light doesn't come on.

The belt is fine.

Thanks

Co_94_PU

iTrader: (-1)

Assuming you blower works on the heat setting.

You'll want to check the the AC fuse power at both sides?
Then the switch. It just pulls out, no idea why the book says to take out the glovebox Worst FSM page ever! The test listed doesn't verify the switch, or the schematic is wrong, it tests the LED but doesn't tell you it's doing so which means you could plug the DMM up wrong and get a false reading.

With the switch removed. Press the button in and..

Test for continuity (Diode mode on your DMM) between #1(Power in) and #3(Power out) this verifies the switch is good, next test the LED #1(power) and #2(LED Ground).

So assuming the switch works, the LED is sort of irrelvant but handy. The next item inline is the pressure switch, then the AC amplifier. Going to skip both of those and test the AC compressor clutch recieves power.

Locate the Single wire plug going to the AC compressor in the engine compartment, it's a single wire plug and probably grey. With the engine running and the AC on you should have power on this wire.

Hopefully you have power here which means the electronic clutch is bad. 'cause I don't wanna explain the rest. If you don't have power here check the sight gauge and make sure you have refrigerant, and report back, you can save some time by removing the glove box to get at the AC amplifier and run those continuity and voltage tests.

hockey88fan

Excellent! Thanks for detailed write up and the time it took you to do so, I appreciate that!!

wyoming9

iTrader: (1)

The very first thing you do is pull a vacuum and see if you can!!

Then see how long it holds!

I am surprised at you people no star for you!

It does no good to chase other problems till you know the system does not have massive leaks.

It has not worked for over two years and who knows how long before that.

It is quite a different thing if it just quit coming home from the quicky mart

oldblue

first step check for available voltage at the switch. if not, start looking for where it gets voltage, i.e. fuse. if it is getting voltage, press the switch and see if voltage is now coming in and going out. report back. you more than likely are also low or out of refrigerant, but you may have an electrical issue as well.

Co_94_PU

iTrader: (-1)

Ow guys really?

He already knows there is some electrical issue the light doesn't come on, no way for it not to come on unless it's a bad LED or not getting power down stream of the fuse. (AC circuit)

Vacuum on a charged system = bad idea. I see where you are coming from but you want to check the sight gauge first, only tool needed there is maybe a flashlight. I reckon you could poke at the service valve also, but it's frowned upon
Here is the proper way from the manual.

highonpottery

iTrader: (1)

I could be wrong but doesn't the AC button light up when the compressor kicks on, and the compressor will only go on if the sensor inside sees enough refrigerant in the system, thus telling it its safe to run?

wyoming9

iTrader: (1)

To pull a vacuum you need to have your manifold gauges on I guess you could do it some other way.

I see people dump so much money chasing other problems to find out the Evap coil is full of holes

In any case it is a moot point

It is the way I would start on any AC system that has not been used in years old habits .

nuff said

Co_94_PU

iTrader: (-1)

I Think I've read that also, but it's not the case. If you look at the A/C system diagrams and explainations, note the light and the amplifier recieve power thru the same wire. The amplifier is effectivly the computer/logic-control it reads various signals, ignition pulses pressure sensor ect, and either activates the compressor clutch or doesn't based on the various inputs.

so no light = no power no ground or a bad light. Pretty sure my systems not pressurized, has no belt, and my light works as expected.

Don't forget you have to turn the fan on to atleast low to have power at the A/C fuse. I think I forgot to mention that before.

HF Will sell you a set of A/C manifold gauges and vacuum pump, for about what I'd expect to pay to have the system pressure tested and recharged. But then again I'm an old fart and usually way off on modern price expectations