I have a 1998 S70 whose A/C would just not work! It was to the dealer twice, an independent shop and I tested everything, the sensors, the relays, etc. I could jump out the A/C relay and the compressor would run, but the ECU wouldn't turn on the A/C. I struggled with this problem for months! I even swapped out the ECU and MCC panel with known good panels. In addition, the car had a intermittent miss at 70 mph. No dice!

I have heard of this A/C and miss problem on the board and from several mechanics too. I found the solution here at the brickboard from one of your members and I think it is the cause of a number of electrical troubles besides the ones above. This repair fixed both problems immediately!

The problem is that the contacts between the ECU and the wiring harness have corrosion or contamination. This is easy to correct and costs less than $20. Basically, you clean the contacts with contact cleaner and dry clean air (not shop air which has oil).

I have detailed the repair on this page http://wolfftech.net/html/volvo.html at my web site. This apparently is a major problem which probably should be a service bulletin.

I hope this helps many of you out!