Yes, the ground issue came to mind, but then after closely examining what is common to the system (as best I can gauge from the poor schematics I have), I began to wonder about the ECU. That brain box provides a lot of inputs to the gauges and the OD unit. I thought I might be able to borrow a unit from a parts Volvo I have, but the two units are slightly different. I have a buddy with a newer Volvo 240 Parts Car that should have the same brain, so I'm going to try to swap that out as it's an easy swap. As far as the ground idea goes, I'm not sure where to start. From the schematic, it appears that the grounds are provided by such things as the Park Brake Switch, Intake Manifold, etc. Knowing that the brake lights work tells me the ground there is good.

This is an irksome problem, and once I've figured it out, I'm going to forward the fix on to the 240 board administrator as an FAQ, because someone else will have the same problem in future I suspect. I've seen some weird electrical problems in Volvos on occasion (I'm a car dealer in NC), but never anything quite like this, except once in an Audi 5000 and a resistor pack solved that.

I drove this Volvo home last night and noticed this morning that the gauges aren't really working at all now. It also stalled once at a traffic light yesterday afternoon at idle and I ahd to bump up the idle speed to compensate for it. Maybe changing out the computer will affect that too. I hate to "shotgun troubleshoot", but some of these parts are quite expensive, so if I can swap to check them first, that at least saves time and $$$!

Cheers~
Keith
www.angelfire.com/nc/jandtautomart