OVP relay?
 

1992 400SE

Speedo quit working. Rear brake pad light on.

Car runs fine.
Had a dead battery and was jumpstarted before the speedo died.

Somebody mentioned OVP. Yet another thread that popped up on an OVP search mentioned OVP for somebody whose car wouldn't run. What systems are plumbed thru the OVP? Where is it?

thanks

The OVP or Over Voltage Protection relay prevents sensitive and expensive components from getting fried due to a current surge or something of that sort.

The earlier "defective" units had loose solder joints that would cause hot start issues, rough idles, and such, but you can pull the whole unit off and it won't prevent your vehicle from operating. These units have a fuse on the top, and a blown one would be the culprit to a rough idle issue.

Anyway, I would look elsewhere for the problem...it ain't the OVP.

Also I don't understand "rear brake pad light"? The sensors are generally attached to the fronts only, and don't indicate which pads are in need of replacement.

Speedo gone out? Is yours an electronic unit? Didn't think they were until later (my 93 is mechanical).

I believe the pad light and the speedo are isolated issues. I would start by checking fuses first...it's the easiest (and cheapest) place to start...

I may be mistaken, but I don't think this model had an OVP relay.

Nope, but I think you're on the right track. It has a module called the Base module. It's on the right side under the hood, way back by the firewall. There is a box you need to access with all the control modules in it. Find the one with a clear plastic rectangular window, there are fuses under that window, check them, I bet one is blown. These are the plastic fuses like GM uses. Don't worry about fuses being "missing", just check for blown ones.

Gilly