1990 Volvo 740T AC Compressor won't turn on

chrismc410 · Post by **chrismc410** » 24 Aug 2013, 10:05

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Hi,

This is my first post and here is my issue:

My 1990 Volvo 740 Turbo's AC compressor will not turn on. I've tried bypassing the low pressure switch to no avail. I took it to my mechanic, it does come on if direct connected to battery. I've read on this and other forums that it could be the switch on the control panel but I don't think that applies to me since I have the control panel type as shown/attached.

My mechanic can bypass whatever it is, connect a toggle switch and force it on via the switch but that is a solution of last resort. Is there a separate relay in my case since the common control panel fix doesn't apply to me and if so, what is the part number or relay type that can be used for the relay if any applies.

Thanks for any assistance.

rrussell · Post by **rrussell** » 25 Aug 2013, 10:56

http://www.ohio.edu/people/ridgely/Volv ... agrams.pdf

Might help diagnose your problem

Figure 7 (C-27) is the a/c delay relay

chrismc410 · Post by **chrismc410** » 26 Aug 2013, 19:47

I narrowed it down to the relay. It will work if the relay points corresponding to posts 15 and 87 on the relay and if the low pressure switch is bypassed, no freon it it. and the solder points on the relay look corroded. I found the relay 1363449, but its either unavailable or expensive. I did find a possible cheaper solution, Autozone has a 12VDC 40A (only source close to me for parts) 4 pronged in the same style as the original, SPST relay. Will this work in place of the original? The OEM is 12VDC 5A. I don't see why it wouldn't work.

Any thoughts to using the generic relay or it must be the original?

Thanks

rrussell · Post by **rrussell** » 27 Aug 2013, 06:39

Dont really know your model very well, but a relay is a relay. Long as its rated for the load, and provides proper enviromental protection for its location.

I have found that the relays in these older volvos are usually repairable with a ohm meter and a soldering gun. They dont makem like they used to.

chrismc410 · Post by **chrismc410** » 29 Aug 2013, 18:29

The generic relay worked, was able to get it to charge without jumping the low pressure switch and now works perfectly. Thanks.