1987 300 SDL electrical problem
 

Off and on (for a few years) the right front parking light will not work. After 1-6 weeks it works again; then it's off again for a period of perhaps 3 days to 2 months. The turn signal light always works. Sometimes if I pound on the light lens, it comes back on; thus I don't think that it is the headlight switch. So, does anyone know where the ground wire for the parking light is? AND, does anyone have any suggestions as to what to check? I switched the bulb with the left side, and switched the ceramic socket adapter (?) with the the left side and still the same problem, while the left side always works. Going over bumps doesn't help. So.....help!

It must be something internal to the light assembly, such as corrosion of the socket. The RH turn signal and Parking light both ground at G101 on the radiator support.

When the light goes out, any warning light on the dash?
 

It could be the light monitoring relay inside the fuse box. It is the longest relay, about 1" x 6". It's function is to monitor the lights and gives a warning light on the dash if one of the bulb is busted. Try re-seat the relay first or get a replacement from the JY. There are plenty of junk W126 cars.

Yes,when the parking light is out, the dash light comes on. Will check the relay as you suggested. Thanks.

Bump.....

Interesting I have this exact same problem on my 124, same light and everything.

I suspect the monitoring relay has an intermittent connection inside based on earlier troubleshooting attempts.

If I get some time this weekend I will dig into it and post back.

Pushed the relay around to make sure the contacts were clean. Now I'll have to wait a few months to see if the light goes out! Let me know what you find. Thanks.

Any other ideas out there?

It ended up being a bad connection inside the monitoring relay.

The pin X3:7 had a loose riveted connection to the brass strap that ends up soldered to the board. I was able to heat up the rivet and strap and apply some solder to the rivet head and strap.

This pin feeds "right parking light" voltage to the right front parking light bulb.

Thanks, I'll try that. The people on this forum have been great through the years offering super, money saving info. This forum is the reason that I can tell people that the SDL has been the cheapest car to keep on the road of all the cars that I've owned.

So pounding on the lens was just a coincidence repair? Corrosion of the socket is the most typical problem I've seen on various cars. It might be more than one problem causing the symptom.

jay bob: I must have a different relay from you. Mine has 2 opposing (1 inch apart) circuit boards perpendicular to the rivet(pins) so that i can see most of the pin-brass strap connections , but I can't get to them. Also my pins are numbered 1 to 8, 1to 16,and 1 to 10. Any thoughts and can you give me the pin number again? Thanks

Yes that is the right relay.

Part number 126 542 01 32 is what is in my car and is probably what you have too.

There are 3 banks of pins:

X1 is the 16 pin group
X2 is the 10 pin group
X3 is the 8 pin group

X3 pin 7 is the output for the right front parking light. Fortunately it is right in the corner where you can get to it with the soldering iron, without having to disassemble the relay.

Be careful, that pin gets HOT after you solder it (don't ask how I found that out). Also be careful not to overheat the pin or you will cause the housing to melt.

OK, I'll give it a try.

SD Blue: The pounding on the lens doesn't seem to help any more. I didn't record when I changed the bulb and the adapter, so maybe that did help.