Since you asked and I happen to own a 87 non-turbo also bought for 400 bucks but have had to put two grand into it since. Anywho I was over at the dealer yesterday picking up some ac parts so I can have ac after moving back to Arizona. The parts guy turns out to be a volvo guru who messes with these things at home. Where was this guy a year ago? He told me the problems he sees the most are the three grounding points being corroded or being loose. The first one is on the drivers side up around behind the lights or down from there. The second is up around the intake man and the third is on the transmission. He said if you take the center console out you will see it.

I hope your car is in better shape than my was when I got it. Check the electrical harness they are known to be bad. Also I had on and off problems with relays. I finally got it sqarred away two months ago. Anywho let us know what you find and what you don't. This is a great site and the guys are great here.