Hello, I did some internet searching and people seem to suggest my issue may be related to an OVP relay. Looking for others' input.

So here is my issue.

When I start my 1986 300SDL, it starts up ok, but it will run real rough. Everything electrical and guage wise seems to work, except the tachometer just sits there and the antilock light is on. This started happening just in the mornings when its cooler, and then after the car would warm up a little (at which point it doesn't run so rough) or just seemingly randomly, the antilock light would go out, the tach would start working, and the engine would run smoother, as if the computer had just all of a sudden kicked on.

Its now happening every time I start it, and I can go 60 miles or more without it fixing itself. These are the only symptoms I am noticing so far.

One issue that may be totally unrelated, during the summer I noticed that my AC seems to work pretty well when its under 90 degrees outside, but when its over 90, I can't have it on auto or it will start to slowly warm, instead I have to leave it on low to keep it blowing cold. I checked my AC pressure and it is fine. The system has been updated (prior to me buying it) to the new stuff. I never went further than that with the AC as the summer was ending and I decided I could live with it till next year.

So, anyone with lots of experience, I would be super appreciative.

Thanks

 

Thanks for the reply. But, in my case they are definitely all related to each other (except maybe the AC). The rough engine, the tach, and the antilock brake late all started at the same time, and as soon as the antilock light goes out (when it fixes itself at random times), the tach starts working and the engine runs normal. They are not happening independently...

 

it sounds like your ovp is working intermittent.you probobly need a new one.i sed to tap mine in morning till new one was delivered.