Thanks for your reply, Klaus, I have plenty of heat in the car once the engine warms up, so I know the antifreeze is getting hot and I'm not thinking my thermostat is stuck open. Besides, that would only create an issue after warmup (or what should be warmup), but mine is there and worse at startup.

I had seen mentions of the DIM, but didn't know it was in the instrument cluster. I guess that could be my issue too. Just one more computer to go bad and make craziness.

The one issue I can't think how to pin on a possible bad coolant temp sender is that the odometers aren't working.

It happens that I also have a 2000 V70 which uses the same temp sensor and the same ABS controller so I can swap those parts for testing if I can find a day when both cars can be laid up. I've been leery of putting the ABS controller from the S80 in the V70 though because of my original theory that bad ABS info was causing everything else. I think that theory is fairly discredited at this point though.

If I prove that my temp sender is working then I guess I'll have to pay Glasgow in Saint Paul to give me more bad news.