My air conditioning compressor won't kick in....an intermittent problem. It works fine for a week then for some unknown reason refuses to run.

I'm wondering if anyone has the computer codes for airconditioning? By the way, I don't have automatic climate control, just the manual type.

I don't think there is any computer control of the manual A/C; hence no codes. How's your freon level? Have you been through a recharge or evaporator replacement yet? If not, a 1994 model almost certainly will experience the problem, whose symptoms are a cycling compressor which eventually won't come on at all due to a pressure limit switch.

There is a way to briefly defeat this limit switch as a diagnostic for low freon charge. Maybe someone else can point out where the switch is and how to do it. (I haven't done it.)

Gerald C

The freon level is fine. I just had it topped up to be sure that wasn't the problem. I also found the low pressure switch, disconnected it and crossed the power leads. Still the compressor wouldn't kick in. It just seems to be an intermittent electrical problem. It works fine for a week then takes a week holiday!!

1. Where do I find the power supply lead to the clutch?
2. Assuming I find power to the clutch is OK I assumet he problem must be either the clutch, the compressor, the high pressure switch or the high temperature sensor inside the compressor. How do I narrow down the problem without removing and replacing everything?
3. If there is no power going to the clutch, it could be the relay. Shouldn't I hear a clicking sound when it's working from under the passenger side dashboard?
Is there a test I can do on the relay? Can I bypass the relay entirely?

Yes it is easy to bypass the relay. Remove the glove box. It is held in with about 6 or 8 torx screws. You do not remove the door, however you need to release the two circular door supports at each side of the glovebox. This is easy also. On the door next to each of the supports, you will see a small hole/slot. Just take something thin like an awl or ice pick and push it into the hole and towards the support and back the support out of it's slot. You are releasing a tab with the awl. The supports will have a tendancy to fall back into the dash. Not a big problem - if you drop one back in there, remove the knee bolster (3 Torx screws) and retrieve it. Kind of tricky to remove the glovebox. It just pulls away from the dash, but if like mine, the plastic will be semi-welded to the dash plastic from time heat and pressure. Pull gently and it will eventually come loose. You must also flex it around the door latch at the top.

Look to the back and you will see two relays in sockets. The one nearest the driver is for the fan. It engages when you move the fan to position 4. The one on the passenger side is for the A/C. It has four contacts. Contacts 30 and 87 are the switched contacts. Contact 30 is the input and connected to B+ (All the time, I believe)and contact 87 is the output. Cotact 86 is the control input to the relay coil. It gets B+ when the A/C switch and fan switch are both on. Contact 85 is "ground", but it is not connected to the chassis, it is controlled by the ECU. To check if your relay is bad, make a small jumper from a piece of wire and a couple of 0.25" spade lugs. Use this jumper to connect contact 30 to 87 in the realy socket. If your compressor kicks on you probably have a bad relay. If not you are in the same boat with me.

The rest I know is after the relay closes, the power is routed through a multi-pin connector that sits on top of the drive side shock tower then goes to the low pressure switch and on to the compressor clutch. It may also be routed through a switch located near the reciever. This is where it gets sketchy for me. My 94 has switch/sensor located here wih 4 wires, others have 3 wire contact here. Still learning.

Hope this helps. BTW I picked up a couple of spare relays at the PNP the other day for a couple of dollars each. The original relay has a reverse biased diode in parallell with the relay coil, contacts 86 and 85 to snub any reverse voltage generated when the coil is opened. I figure this is an important feature since the ground is controlled by the ECU. The diode is protection for this circuit. The 40 Amp Bosch relays I pulled out of a dead Audi have a resistor for the same purpose, but I may solder an external diode to the contacts if I end up needing the relay.

Keep posting any info you find. May help me also.

Dan

Sorry, I can't help more. You should definitely do a search on the Bay13 forum, though:

http://www.volvospeed.com/vs_forum/index.php?showforum=3

Gerald C

Thanks for the tip. I'll give this a try.

I am wrestling with brakes on the '90 240 right now. I have to sit in 90+ degree weather for a while longer I guess.

Dan W.