Air Conditioning and heater troubles

[fatboy0186]

For quite some time now, the A/C has not worked on my '91 XLT. I had allmos everything replaced, except the clutch and compressor. When I cut the A/C on, it just blows hot air and the clutch does not appear to engage.

Also, even when I switch the heat/vent off, hot air still comes out of the vents. What is up with this? I had the heater core replaced a while ago, could this have been installed wrong? Thanks for any help.

 

[unpredictable1]

my 93 Eddie Bauer had a similar problem, it would just blow hot air.

had a rebuilt compressor done, clutch assembly was still good, (you could see it engage) and also i was converted to the new A/C setup...R32? er sumthin.

but anyways a rebuilt compressor sounds like it'll do the job for ya, but you may need that clutch assembly, if it don't come with your rebuilt compressor.

as for the air always coming through the vents even when you turn it off, not sure what that is, probably a faulty switch in your dash heater/ A/C controls.

hope this helps...

leo

 

[Robb]

You may want to put a voltmeter on the clutch wire and see if you are getting 12v to the clutch. If you are, the clutch is shot. THis will help narrow down what the problem my be.

It would be very hard to install a heater core wrong. That shouldn't be a problem.

Robb

BTW: Where are you in Richmond?

 

[fatboy0186]

I'm in the Bon Air area, not acctally in Richmond, but right on the edge. I tried to measure the voltage, but I couldn;t get a reading. It may have been beacuase I couldn;t get my test leads to touch the wires. I also may have done this wrong. I turned on the power and turned on the A/C. Then I unplugged the plug that connects to the compressor and tried to put one test lead in each of the holes in the plug. Is this right?

 

[TDG]

Yup thats the right way of doing it, if you get no voltage to it and you have a good charge in the AC system you might have a faulty pressure switch which is that "thing" with the wires coming out of it on top of the accumulator canister which is on the passenger side of the engine compartment near the blower motor to the left of the AC/heater box. If you do get voltage to the compressor clutch but it still won't cycle you either have a bad clutch (can be tested buy connecting directly to the battery) or the pressure switch might be weak and unable to pass the current needed to cycle the clutch even though you have voltage at the leads. The latter happend to me and made for a very interesting night of troubleshooting.

 

[fatboy0186]

Alright, I just got a new clutch cycling switch. Are there any precautions I should take before its install, such as high pressure? Thanks

 

[TDG]

It should be as easy as unscrewing the old one screwing on the new one, there is a tire valve stem style valve underneath the pressure switch that should shut off when you unscrew it. I would wear eye protection in the unlikely event that it doesn't shut off or isn't there. You should hear a light hissing sound as you unscrew the old one and screw on the new one which is the valve closing and opening. Good luck.

 

[fatboy0186]

I just put the new switch in, but it still doesn;t work. I tried to measure the voltage at the compressor, but I got no reading. What else could be wrong? I'm going to check the wires now to make sure I have current running through them. Thanks for your help with the switch, I think mine was broken anyways, and it's good to have the new one on there.

 

[fatboy0186]

Ok, I just checked the continuity on the two wires that run from the pressure switch to the compressor. I got a connection on the black wire with the yellow stripe, but I could not get a connection on the solid black wire. I am guessing that the solid black wire is ground, but I should still be able to get a connection on the wire. Is this wire not working anymore? And do the two wires at the compressor connect directly to the pressure swtich?

 

[TDG]

Ok, the solid black wire on the clutch plug is tied to ground so you won't get any voltage off of it but you should get a good connection if you measure to ground.

The black/yellow ties back to the WOT cutoff relay which cutoffs the AC when you floor it.

From the WOT cutoff relay it goes to the cycling switch be means of the dark green/orange wire.

The purple wire is the feed into the cycling switch from the panel switch and should have voltage on it when the ignition is on and the AC switch is pushed in with the orange light on.

I would pull the plug off of the switch and test at the purple wire for voltage with the ignition on and the AC switch on at the panel, make sure the orange light is coming on.

If you have voltage there then check for a closed circuit (continuity) across the cycling/pressure switch, if the circuit isn't closed then switch might be faulty or there isn't enough pressure in the AC system to close it. It normally closes at around 45 psi.

 

[fatboy0186]

I just checked all the wires. I have 11.8 volts at the purple wire, and have continuity on all the wires. I checked for a closed circuit on the pressure switch, but it was open. I had the A/C system filled with freon and had a bunch oh stuff replaced a year or two ago, so I guess that I have a leak somewhere in the system. Any places I should check before I take it to the A/C guy? Thanks for your help guys, it has helped me to narrow down the problem.

 

[fatboy0186]

Oh, how tight should the pressure switch be? I only tightened it up a little with a wrench.

 

[TDG]

Thats about all it should take to tighten it down any more than a little bit will crack the plastic base.

Just to be sure you could get a pressure gauge for AC systems and check to see how much pressure is on the low side.