The AC on my Wifes 1993 940 A/C stopped working. I hooked up my AC gauges to the low side, but haven't found where to hook up the high side gauge. It isn't entirely necessary for me to connect the high side, but I would like to if there is a 'port'. Is there a high pressure AC test port?

Anyway, it was a little low, but I topped it off (a few lbs above ambient temp.). I have no voltage getting to the AC compressor. I had pulled the grill (while looking for the high side port) and saw what seems to be a high pressure cut-out, a low speed condensor fan, and a high speed condensor fan switchs. I also found the low pressure switch right near the low side gauge port.

After jumping 12volts to the compressor, I found that the system works fine. The low pressure switch cuts in around 20lbs and out around 40lbs (from where it 'clicks', I haven't used a multimeter on it yet though). The Condensor fan comes on and off also (I can't remember the pressures). I have checked the 30 amp fuse and it is fine. I have played with the switch on the dash, but haven't pulled it out to check it yet. I did 'jump' the low pressure switch (shorted the connection) just to see if it was a bad switch, but the compressor didn't come on, so I don't think that the low pressure switch is bad.

So, my questions are:
1) Can I hook up my high side gauge? (and where?)
2) Is there a 'common' problem with these cars? (bad switch, or relay)?
3) Does anyone have a Photo on how to remove the radio? I hear that there you insert a screwdriver and pull, but I don't have "a square hole at each side of the radio"...

Thanks in advance for any and all help. I have an idea of what I need to do next, but any direction would be appreciated.

1. There is not any high side port on those cars.
2. If you have the manual controls there is a solder connection that gets hot and comes apart and then you loose power for the system.
3. It has been a while for the radio but I think the slots are behind the radio knobs.

1) Thanks, I had figured (I really had looked ALL over...)
2) No manual controls. I have removed the control panel today, no visual defects. I didn't delve to deeply though, because I feared that removing the 'Vacuum hose harness' might create more problems.
3) THANK YOU, THANK YOU, THANK YOU!!! YOU ARE SPOT ON! I only wish that I had seen your reply! I searched all over and could find that simple trick. I ended up pulling the radio from my 740 and seeing what held it in. The tabs on that radio are tapered to allow you to pull it out with brute force. The tabs on the 940's radio (CR-815) are 'squared' and won't come out with brute force without breaking something. Simply pulling the knobs off and prying the tabs with a small screwdriver did the trick. I will have to make another post explaining it, maybe with pics, so that if someone else googles it, they will find the answer!

I guess my next move is to get a Wiring Diagram for the AC system and trace out the defect first. That way, I won't change the HVAC head (the control panel) unless I need to.

Who can suggest the best place to locate the AC Schematic for a '93 940? I have heard that I can get the whole set of manuals on a CD-Rom for about $35. I will have to check that out. Any suggestions?

Does the head unit on the 740 look the same as your 940?
If you have vaccum lines going to the back of the A/C control head then it is a manual setup.

If the A/C control heads are the same try swapping them out and see if it works.

I was going to post that before but got distracted and forgot to come back and post that.

I was mistaken when I put that there are no manual controls. I don't know what I was thinking :blush: .
The unit in the 940 has: three dials (fan speed, duct selector, + temp.) and two push buttons (re-circulation + A/C off). I did check the unit in the 740 and it is very different. I didn't see that I could swap it at all (BTW: it has one dial (fan speed) and two levers: one for duct selection (first two spots are for ac on) and the other one is for temperature. I can't remember what was so very different (other then layout) but it must have been all of the connections. I was hoping to be able to try the 740 controls in the 940.

I will have to pull out the head again and take it apart to see if there is a broken solder connection. Hopefully one day this week (I work nights).

OK, I have pulled it apart again today and really tore down the HVAC controller. It was rather simple, but time consuming. There aren't any visible defects on the circuit board, and there are only 2 pairs of wires coming off of it (not including the harnesses of course). One set of wires is for the lights, and the other is for the AC. The board needed to be removed from the base to access it better and I found that there was constant continuity no matter what position the switch was in. The switch itself only acuautes a portion of the vacuum control and the wires come out from the vacuum control itself. I wasn't about to pull that apart, so I re-assembled the whole unit (I was lucky to find the 'detent' ball bearing that had fallen out from the temp control know assembly, and I put it all back together properly).

After re-assembly, I re-tested it in the car, and it was now alternating between open and closed as I worked the switch! I re-installed the board and then the HVAC head and.... Nothing.... Oh well. I traced the lead from the compressor through the low pressure switch and into the HVAC head. I jumped voltage to it and the AC works fine (I added just a bit more freon).

I have a lead to go on in getting another HVAC head (used), I will also call the Dealer tomorrow and price one from there (just for laughs). I have pretty much decided that if the part is over $50, I will just add a 'lighted' dash mounted switch (through a relay) and feed the circuit from there. I am not willing to spend $100 on this part. Let's see what happens and I will let you know how things turn out.

A very common problem is a bad solder of one of the connections on the circuit board of the controls. You can only see a small darking around the edge of the connection. Go to Brickboard.com FAQ for details on how to find and fix the problem.

Ahhh, after a bit of digging I found THIS! I pulled it out and again checked the board, this time paying close attention to the contacts mentioned. Again, I noticed nothing... I couldn't find my small soldering iron (Butane powered), so I grabbed my BIG Gun (yeah, yeah, it was stupid... :blush: ). Well I resoldered the four pins fine, but I did drip some solder on another circuit below where I was working (darn big gun, just not meant for this type of work). I cleaned up the lower spot and loosened a connection while trying to fix it. Well, I put it back in and the AC WORKS!

BUT..... That pin I messed up was where the heater rheostat ribbon cable connects to the board :( . So now the heat doesn't work. I drove up to Radio Shack to buy a new Butane soldering iron and tried fixing the connection again.... Still no good. Before I ruined the board I drove to a marine electronics shop and asked if he could re-solder the connection, he said for $30 with no sorts of guarantees he would. I asked if the connection would be good (I know the rest of the board was good) and he kept on saying no guarentees. I thanked him and left. I drove a little further to the next electronics repair shop (this one a TV/Electronics repair shop) and the guy fixed it for $20. I had told them both that just running a 'jumper' wire in place of the printed circuit was fine by me, if they thought that I had damaged the printed circuit. Well, that is what he did. He also gave no guarentee, but I am most certain that it will be fine.

My wife took the car while I was running around and so I can't test it out. I'll install it tomorrow.

BTW: What is the typical cost for one of these? I assume around $50 at a junkyard, but I haven't gotten a price yet.

From the dealer it is like almost $400.00.
I would look in the junk yard.

Well, it is all re-assembled and everything seems to be working fine :banana: !

I want to thank you all for steering me in the right direction to get this repaired. I honestly would not have spent $400 on replacing the HVAC Panel, I would have wired in a 'new' AC switch and mounted it on the dash between the ignition switch and the HVAC Panel. Of course, repairing the existing item was preferred and I certainly would never have known to re-solder the "Relay" lugs without your help :liebe011: .

All-in-all, a whopping $22 in tools (a new Butane soldering iron (I still can't find my old one)) and $22 in repairs to the heating circuit (which I messed up by trying to use my BIG Gun). $44 is more then wiring in a new switch, but far less then a new/used HVAC. It's certainly nicer to have the 'factory' button working rather then an aftermarket switch/relay/fuse that I would have installed.

To all that have helped me, I hoist a 'virtual beer' in thanks :beer: !

-Ken

BTW: By all means if there is anything I can do to help you guys out, let me know. I happed to be pretty good with computer repairs and have several leads to get good prices on new/used PC hardware/software.

We do what we can to help :beer:

Well, I thank you for the help that you have given me so far :thumbsup: .

See my latest post for a 'draw' that keeps killing the battery.

Ohh well.... It seems that the HVAC Controller has died again... I pulled it out and rechecked the solders. I found that if I ground one of the relay lugs with a test light, the AC comes on again. I resoldered the 16 Connector pins and all 4 relay pins again. Still nothing. I am looking for a used one. I just emailed a guy parting out a '92 960 in the F/S section. I hope he has the same MCC.

In the meanwhile, I have soldered a feed wire onto the terminal for the AC compressor (green/red wire, #10 on the plug) and connected it to a Cigarette lighter plug (I currently have a 5A fuse in it). So now, my Wife has to plug in the plug if she wants AC.

Hey, it's a temporary fix until I can locate a MCC. Any leads on finding one would be greatly appreciated. I might just install a 'lighted' switch on the left hand side of her dash (the sunroof/defroster switches are on the right side) where I would guess the fog lamp switch would be. I figure that I will pull a feed from the Cigarette lighter since it is a 30A Ignition-On feed and just wire is so that when the button is pushed the switch lights up and the AC comes on. I figure that doing it that way will elminate the High Pressure switch though, so I might just run the ground through the High Pressure Switch to keep from possibly having a serious failure.

-Thanks, Ken.

As long as the cooling stsyem is working good then there really isn't a need fo the high pressure switch.I also think the system has a blow off valve if it gets to high it will just blow the freon out.

I wish you were closer I have a MCC panel in the garage but forget if it is good or not.I think it is but not sure.

Don't give up. The first time I tried to resolder one it only lasred 2 days.

The second try I jumpered between the pins by solodering a bare piece of wire between them. See 2'nd and 3rd Pics.

deadken - my son has a 93' 940 with the same issue. Looks like I can build on your experience. How did you get the controller out, the manual indicates full removal of the dash.