A/c Not working 96 GQ

[The Turdinator]

Cant get my A/C working, dose anyone know how to test the relay in engine bay or know of other problems? Thanks

[YNOT]

Your A/C may have a leak and lost its gas. The low pressure cut out switch will not allow the compressor to cut in if it is out of gas. A quick test for this is to bridge the 2 wires going to the cut out switch, if the compressor cuts in it's out of gas.

Tony

[The Turdinator]

thanks tony, would that even cut out the blue light on the ac button. as u push the button and it dosent even light up or change the revs in the motor

[YNOT]

The revs only change when the compressor cuts in and puts load on the engine.

The light in the switch not working could be either no power getting to it or a blown bulb. Have you checked all the fuses?

Tony

[Yendor]

For the A/C to work the interior fan must be on, if the light in the A/C button doesn't light up when on (with interior fan on) then you either have a blown bulb in the switch or a blown fuse.

If the fuses are ok, then as Tony has said try bypassing the low pressure switch, if you then hear a clunk (A/C compressor cutting in) and the engine RPM increase, this indicates that your A/C system is low or out of gas.

[The Turdinator]

cheers thanks guys

[canuck]

The coil for the AC clutch can go too, so if the other points don't turn out the cause, then check there. You should be able to see if you are low on gas through the slight glass.

[BigMav]

Ok I recently fixed my a/c so will try and give you some tips for one of my first posts. Firstly you will need a test light or a multimeter. Check things in this order.

1. Is there power at both sides of the fuse on the drivers kick panel?

2. From the fuse the next place to check for power is at the switch, don't worry about the light mine has never worked its just a bulb. Check there is power on one side and then check the other side when you push the button. All good so far?

3. Next place is the thermostat, you need to unscrew about 6 screws on your glovebox and you will easily see the thermostat mounted on the plastic box with two wires coming off it. Check here, this is actually a switch too so you might have to tweak the knob if you only have power on one side. If you only have power on one side then this is faulty. To confirm it is the thermostat there is a small capillary tube which goes into the evaporator. You really can't miss it.

4. Next stop, under the black panel next to your battery there is an a/c relay which should be labeled as such. you should have power at this relay too and if you are keen you can test the relay with a couple of pieces of wire and checking with a multimeter. Ask if you're not sure how.

5. Then you have your low pressure switch to test for power at, which has already been mentioned.

6. From there the last place is the connector at your A/C compressor.

That pretty much somes up the aircon power circuit so hope it helps. Before you do any of that take one of the caps of and depress the valve quickly to see if there is any pressure in the system. Oh and checking the sight glass won't help until you get the compressor running. Hopefully at least some of that is helpful.

Cheers
Jon

[Bigrig]

Ok I recently fixed my a/c so will try and give you some tips for one of my first posts. Firstly you will need a test light or a multimeter. Check things in this order.

1. Is there power at both sides of the fuse on the drivers kick panel?

2. From the fuse the next place to check for power is at the switch, don't worry about the light mine has never worked its just a bulb. Check there is power on one side and then check the other side when you push the button. All good so far?

3. Next place is the thermostat, you need to unscrew about 6 screws on your glovebox and you will easily see the thermostat mounted on the plastic box with two wires coming off it. Check here, this is actually a switch too so you might have to tweak the knob if you only have power on one side. If you only have power on one side then this is faulty. To confirm it is the thermostat there is a small capillary tube which goes into the evaporator. You really can't miss it.

4. Next stop, under the black panel next to your battery there is an a/c relay which should be labeled as such. you should have power at this relay too and if you are keen you can test the relay with a couple of pieces of wire and checking with a multimeter. Ask if you're not sure how.

5. Then you have your low pressure switch to test for power at, which has already been mentioned.

6. From there the last place is the connector at your A/C compressor.

That pretty much somes up the aircon power circuit so hope it helps. Before you do any of that take one of the caps of and depress the valve quickly to see if there is any pressure in the system. Oh and checking the sight glass won't help until you get the compressor running. Hopefully at least some of that is helpful.

Cheers
Jon

Outstanding post - many thanks ... going to have a hunt tomorrow as mine is working on and off when it wants (literally) - no pattern to it, just some days it fires up, some it doesn't (and has just been pressure tested and new gas installed).

Fingers crossed.

[MudRunnerTD]

Ok I recently fixed my a/c so will try and give you some tips for one of my first posts. Firstly you will need a test light or a multimeter. Check things in this order.

1. Is there power at both sides of the fuse on the drivers kick panel?

2. From the fuse the next place to check for power is at the switch, don't worry about the light mine has never worked its just a bulb. Check there is power on one side and then check the other side when you push the button. All good so far?

3. Next place is the thermostat, you need to unscrew about 6 screws on your glovebox and you will easily see the thermostat mounted on the plastic box with two wires coming off it. Check here, this is actually a switch too so you might have to tweak the knob if you only have power on one side. If you only have power on one side then this is faulty. To confirm it is the thermostat there is a small capillary tube which goes into the evaporator. You really can't miss it.

4. Next stop, under the black panel next to your battery there is an a/c relay which should be labeled as such. you should have power at this relay too and if you are keen you can test the relay with a couple of pieces of wire and checking with a multimeter. Ask if you're not sure how.

5. Then you have your low pressure switch to test for power at, which has already been mentioned.

6. From there the last place is the connector at your A/C compressor.

That pretty much somes up the aircon power circuit so hope it helps. Before you do any of that take one of the caps of and depress the valve quickly to see if there is any pressure in the system. Oh and checking the sight glass won't help until you get the compressor running. Hopefully at least some of that is helpful.

Cheers
Jon

Excellent post Jon, well done mate. All good info. For problem solving and ease i'd be doing check number 5 first though. get that out ofthe way as its the easiest out of all the check and the most likely problem. If that works then work through the list provided by Jon.

my 2c

FYI, the low pressure switch is mounted to the top of the dryer and on a TD42 that is mounted behind the right hand headlight. Its a control circuit and Positive only. Check for continuity and then power up. 3 minute job.