Mercedes-benz - C-class :: C220 - Inconsistent / Intermittent And Incorrect Warning Light

I have a 1996 Mercedes C220 with 60K miles on it. It runs great, but is giving me fits with inconsistent, intermittent, and (I’m pretty sure) incorrect warning lights, as well as intermittent gas gauge failures.

Soon after I bought the car about six months ago, the oil pressure warning light began to come on intermittently. Each time it came on, I checked the oil level and found it to be full.

At first it would come on, sometimes for just an instant, sometimes for several miles, but then go off and stay off for days or weeks. … Then it got weird … Each day as I was driving to work, the oil pressure light would go on - always within about 100 yards of the exact same place - about 10 miles and 15 minutes from home. It would stay on for 1/4 to 1/2 mile, then go off and stay off until the next day, when it would do the same thing again. I was still checking the oil level every day and finding it to be full; I have never added oil except when I changed it.

About two months ago I changed the oil and the filter. I put in Mobil 1 0W-40. Immediately after I did that, the oil light came on and has stayed on almost permanently. I say “almost” permanently because if I get to highway speed and then accelerate quickly, getting the RPM’s up to about 4500, the light will go off, sometimes for just a few seconds, sometimes for a minute or two, but will always come back on after I slow down.

Weirder still, immediately after I changed the oil, the coolant level warning light came on and has stayed on permanently. I have checked the coolant level every day since then; it has been full every time, has never gone down, and has never needed coolant added.

Here’s another issue that may be related. The gas gauge intermittently drops to empty, even when I know for sure the tank is not empty. Sometimes it shows the correct fuel level, sometimes it shows empty. Sometimes it will bounce back and forth between the two several times within my 1/2 hour drive to and from work. It does this with no pattern I can discern. It has been doing this as long as I have owned the car.

I have hooked up my Actron OBDII code reader to the car several times. It never shows any outstanding codes, any pending codes, or any other problems.

Although these issues worry me a bit, I have been willing to live with them, assuming there’s really nothing wrong with the car. But now I’d like to sell it - for reasons completely unrelated to the warning lights - and I’m pretty sure no sensible person would buy it if they test drove it and saw the warning lights. (And I think most people would notice if I covered them up with electrical tape!)