Look at the FAQ for some troubleshooting guidance.

I too, had problems with the wiring at the positive battery terminal. The wires had corroded up inside the insulation. I cleaned and re-attached all the wires.

Another thing to check are the grounds inside the left front fender, including the grounds on the ignition devices mounted there and the ABS. The FAQ tells you that this is the problem if your car stalls when you turn on the high beams - This is EXACTLY what my '90 turbo did! You might be surprised how many problems are described and solved in the FAQ

Once, when I had some connection problems, my trusty Volvo service writer gave me a tube of Volvo dielectric grease and advised me to clean and grease ALL connections under the hood, and secure any that look shaky with a tie wrap.

I did one connector each week, so that if the car had issues, I knew which connector to look at first. There are a LOT of connections to act up.

Look inside all connectors for pins that may have backed out of the plug. This happened to one of the pins in my mass air flow sensor, causing the car to barely run. It happened during routine maintenance when a tech changed the air filter.

(This guy is pretty good, He works on his own old volvos - once, he had a tech swap the ABS controller from his car to mine in order to try to find a problem!)

I never really had connector problems except when one of our bricks sat around a lot. My theory is that daily use helps keep connections clean by movement of the wires when the car goes over a bump.

Let us know what you find.
--
'96 855R,'64 PV544 driver, '67 P1800 basket case, '95 855, '95 854, the first three are mine, heh, heh, 415,000 miles put on 9 bricks