Troubleshooting A/C problem -- dead ends

I have a 2000 Chrysler Town and Country and I'm trying to troubleshoot my air conditioning, but I'm running into some dead ends.

First off, I get only warm air out of the vents. I checked the compressor to see if it was running, and it was not. The clutch was not engaging at all to turn the compressor. So I thought I had a bad clutch or pulley bearing, but I wanted to first check to see if voltage was getting to the clutch. I checked the connector that plugs into the coil and there was no voltage. So, I went to the relay panel (Power Distribution Center) and unplugged the relay to begin troubleshooting it.

However, before I got into that, I wanted to see if the clutch was working, so I jumpered the relay socket |B| to |D| (see diagram link below) to send power the clutch (engine running, of course). The clutch engaged and the inner ring started turning the compressor. Everything looked good from the outside of the compressor, but I wasn't getting any cold air throught the vents.

This is the part I wasn't sure about. Assuming the compressor and the other parts of the cooling system are good, should I be getting cold air by jumpering it, or does the relay need to be plugged in for the whole system to work?

Aside from that, I still had the problem of voltage not getting to the compressor clutch. So, I started taking voltage measurements on the relay socket and also measurements on the relay contacts with it plugged in. Here's what I got (see diagram for matching letters):

Diagram Link: http://home.comcast.net/~pjsantavicca/index.html (http://home.comcast.net/%7Epjsantavicca/index.html)

Voltage Readings of relay socket (engine running):

|A| to ground: 0.04V
|B| to ground: 0.01V
|C| to ground: 14.0V
|D| to ground: 14.1V
|A| to |C|: 13.5V
|B| to |D|: 14.1V
|A| to (+) on batt: -13.5V
|C| to (+) on batt: -0.01V

Relay plugged into socket (engine running):

|A| to ground: 14.0V
|C| to ground: 14.0V
|A| to |C|: 0.01V


I tested the relay on it's own and it works fine. It just does not seem activate when when it's supposed to, when plugged in. I also tested the voltage on the socket when switching on and off the a/c. I got no differences. I did this with something I knew worked, like the high beam headlights, and I got the expected voltage changes.

The number one cause of no cool air from the A/C is a low refrigerant charge. If it is low, the pressure switch will not allow the system to turn on as a measure to keep the compressor from eating itself. Low charge = no lubrication. The fact you jumpered power to the clutch means you bypassed the pressure switch. The fact you still got hot air is a red flag for a low charge. Hopefully you haven't damaged the compressor. Suggest you have a shop check the charge and reservice. Since you appear to be a hard core DIYer, consider dumping a can of R134 in it, FOLOWING DIRECTIONS TO THE LETTER. This system can kill you. I recommend the first option.

Once the system is recharged, you'll have to find the leak in the system. You or a shop can in inject a die in the system and use a blacklight to inspect for the leak.

Thanks for the reply, RIP. Yeah, I kinda got ahead of myself. I will check the pressures tomorrow. The only reason I didn't is that, before checking it out myself, I had two different shops take a look at it and they said nothing about it being low, and for some reason I assumed that they would have told me if it was. They said that the clutch was not working (which to me it looks like it is). At the time, I asked if they could just replace the clutch, but they said they would only replace the whole compressor and charge me $1000-1600 to fix it.

So, I'll check to see if the pressure is abnormal and report back what I find.

Thanks again.

If you want to talk to some real knowledgeable A/C folks, have a look at A/C forum (http://www.autoacforum.com/). It's *somewhat* of a promotional site, as the forum owner sells A/C equipment, but it appears to be very above board.

There's a lot of discussion about self-charging, the #1 being to not *just* charge from a can, but have a manifold gauge set at the bare minimum to check the pressures. Also warns against just buying any 'ol can of R134A at the auto parts store, as apparently many have some "sealers" in them that you have to be careful about, as they often do a lot more harm than good. You're not saving any money by doing it yourself if you spend $10 on a can of R134A that wipes out $700 worth of A/C equipment.

At the time, I asked if they could just replace the clutch, but they said they would only replace the whole compressor and charge me $1000-1600 to fix it.

While this remark could feasibly come from an extremely conscientious person, it would only come after a significant explanation of the "why" behind it IMO. Otherwise, the shop is just lazy and doesn't want to properly diagnoise the problem IMO. Nothing worse than parts monkeys who go on easter egg hunts when it's not their money. I'd find another shop. A/C work *is* expensive, but from your description, they didn't spend much time diagnosing the problem, so I have little faith that they would be very meticulous about cleaning out the lines,etc. even if they *did* replace the compressor. Dirty lines will trash a brand new compressor in no time flat.

Well I checked the pressure and both the low and high side were under 10 psi. So, it looks like that's my main problem. I'm going to do a bunch more research, then recharge the system and see if the pressure switch will turn on the compressor.

Thanks for the tips and the link to that forum, webbch. I checked it out a little and it looks like there's a lot of good info there.

Glad you found the information useful.

I've always drawn the line at doing my own A/C work: That's one thing I've never felt confident in messing with. However, armed with that A/C forum and the associated store, I think I'll be taking my first steps into A/C repair in the next year or two. It will definitely be a learning process.

Since the pressures are that low I would head straight to a reputable A/C shop. Contaminants (moisture, etc) could easily have been drawn in and could easily decrease the life of the system components. The only way to get rid of any contaminants is to draw a vacuum (suck everything out) on the system before servicing. Unless you want to spend big bucks on that type of equipment it's not feasable for the average DIYer.

You need to spread the word far and wide about the two "shops" that originally looked at your A/C. If ever there was a case of fraudulant
"mechanics" this is it. They either never checked the pressures or checked them, disregarded them, and did their best to rip you off with a completely unnecessary compressor change. Please do everyone in your area a favor and file a complaint with the BBB. In fact, you might want to contact your State's Attorney General office. They are usually a state's consumer affairs advocate.

After I saw that the pressure was low, I decided to add some 134a to the system just to see if the pressure switch would engage the clutch and turn the compressor. It did, but the high and low pressures were the same, so it looks like my compressor might be dead, aside from the leak. Anyone know of a sure way to tell if the compressor is dead? I read somewhere else that if the high and low pressures are equal after adding refrigerant, the compressor is most likely dead, but I wanted to be absolutely certain.

RIP, thanks for the advice, but I'm gonna do some further troubleshooting. I actually do have a vacuum pump, and I think I can fix it myself. I will definitely report the shops because I proved that what they said was incorrect.

I have an 07 Chrysler Town and Country and have always used the same ac shop . I replaced the compressor and spent $900 then 2 yrs later I replaced it again . Now I'm having problems , started with the ac only blowing if I hit the glove box a few times . Then it stopped blowing on all levels except low , then less than low . So I pulled the blower motor and tested it on the battery and it worked great . On the blower motor theres a small box with gears in it, the box was making a funny sound when we hooked the blower motor back up , so we opened the idk what to call it, and oiled the gears till they would spin . So I then replaced the resistor and when I did the air worked for maybe 2 or 3 weeks . Now I'm back to square 1 with no air and noticed the rear air blows but not very cold . I'm also having loud sounds coming from my alternator clutch pulley. Thought I could just replace the pulley but now my van can be driven maybe 6 miles and then my battery light comes on and the battery is new . So idk where to start with the ac or should I replace the alternator or can I just replace the clutch pully . Now I did take the alternator off the van and drive it to O'REILLY to be tested and they tested it 3 times all showing good .