Electrical issue on 91 300sl
 

Hello,

I'm having an intermittent electrical issue on my 300sl. It did this a few days ago so I removed all the fuses under hood & trunk and cleaned all the contacts. When I was done, all was fine until today. The seat belt light comes on (with belt hooked) and the turn indicators will not function, though the 4 way flashers still work. Also, with the light on for seat belts, there is a chime noise for several seconds and then it quits, most likely a signal the belt isn't hooked. Hooking and unhooking the belt made no difference, nor does cycling the 4-way flasher switch. If this was one of my MGB's, or other older cars, I would start re-securing grounds but not quite sure where to start on this. Any assistance greatly appreciated!

the back-rest lock uses the same circuit. my 90 has a couple of screws under the front of the cushion that hold it in place, once removed, lift sharply on the front and it comes out. should be able to put a meter on the buckle switches at the connectors and check wiring and the connection. I can't figure the circuit connection of the seat belts to the turn-signals yet, if there is one. you said you had cleaned the fuses. might look close for a fine crack on 6, 8 and 9 fuses.

It all gets complicated. there are ties to the seat control module under the seat and the air-bag control module. the flasher is part of the combination relay, it's the middle module toward the front of the car in the fuse and relay box behind the drivers side hood hinge. the second largest module in there. question is, why would the hazards work and not the turnsignal?? the part is 201 821 02 42. It's beyond me why there seems to be a tie in with the seat-belts to the turnsignal. unless there's a short, I can't find it on my wiring diagrams. sorry I can't help. when you solve this, please tell us what it was.

Thank you very much for your assistance. Interesting about the seat back lock. Neither worked (released) so I removed the upper upholstery and took the little side cover off by the handle. I adjusted both cables, both sides and got those working. I also disconnected the battery & pulled the power surge relay, checked fuses and checked all the module terminals. Not corroded that I could see but cleaned with contact cleaner & re-installed them. I drove it all weekend after doing those things and couldn't get a repeat problem. I was not able to find the correct fuses (copper) so I ordered a full set & I'll replace those next weekend. I will store it shortly for the Winter but not until I replace the fuses and run it for a bit.

I should probably report back on this that since I've changed the fuses to copper/brass, pulled all the relays and cleaned terminals and adjusted the seat back release cables, we've had no re-occurrence of these problems. Thank you for the tips, greatly appreciated!