bradwilcox

1989 90.

Car was fine until tonight, taking a leisurely drive when it suddenly reports bad brake light. OK fine. Drive another mile. Red coolant icon comes on. I don't think it's a case of very slightly low coolant level, especially when taking a curve -- I've seen that before. Was just going on a straight, flat road tonight. Car was not overheating, anyway. Then both icons begin to alternate quickly along with the annoying beeping. Get home, check things out, everything seems OK. Lights were fine, temp fine.

I think I'll replace the ignition switch. Anyone second that?

Or trunk wiring at the hinges? But I don't have a reason to suspect that at the moment.

Anything else?

bradwilcox

Update:

Suddenly unable to pull codes. Pulled them two weeks ago to investigate another issue, no problem. Now the CEL lights up but stays lit, instead of disappearing in anticipation of codes beginning.

Undid the battery to check connections, especially ground. Looked OK.

Upon reconnecting and turning ignition (but not firing engine over) the radiator fan now goes on instantly. Pulled fuse 20 and it instantly stopped.

Gremlins ...

EuroGuy9622

I've has similar issues with warnings on the dash, seems to be a faulty dash. It's gotten better mostly on it's own but the dash is still 'slow' sometimes. That doesn't explain your rad fan, but if you had just shut your car off sometimes those will kick right on as the car stopped circulating, and coolant stayed hot.
I have a 88 80, pretty sure that's a similar dash and general computer setup. Or, lack there of...

bradwilcox

Thanks for the reply. I hadn't just shut down prior to resetting the battery. The car had sat all night while I pondered the situation. That's why the rad. fan coming on now at ignition is ridiculous.

In reading my Bentley it may be some components of the instrument cluster such as the whole autocheck sub-assembly behind the cluster, or the tiny voltage regulator are faulty all of a sudden.

EuroGuy9622

So I found another piece in the fan switch puzzle that you may already know about. I do not have the Autocheck system like you do, but I believe we both have an ambient air thermo switch. It sends to a timed relay and initiates the fan based on under-hood temp to assist with hot starts. The switch is located on the left of the cylinder head (passenger side) and it looks just like a coolant temp switch, mounted in a bracket. This also links through a device on the back of the instrument cluster.
I don't know in what way this switch can fail but maybe that will end up being helpful. Either way, it's pretty cheap to just start replacing thermo switches on these motors, could be a good start to help verify the cluster.