just bought 86 sdl, scary electrical problems help - PeachParts Mercedes-Benz Forum

covertcourier · #1 06-26-2007, 08:26 PM

My wife is a proud owner of a 1986 SDL with 167,000 miles. We bought it off a mechnic(good guy) where despite sitting for 3 years has no rust and is still aesthetically in very good shape.

Major issue - it was abandoned because the a/c melted down 3 years ago and fried the wires back to the fuse box, where the owner had been compensating with larger and larger fuses.

That said the car runs. I've never turned on the a/c, the light for glow plug is always on, not to mention it eats batteries and the mechanic by-passed the starter with a switch under the dash.

Do i need to replace the engine wiring harness?(expensive) Shoud i try to track down the bad wires which the mechanic tried and stopped.

The car has other problems-holes in the muffler, noisy belt tensioner, nothing too bad though.

and secretly i may like the car more than my perfect 84 300 td wagon it makes me feel like i'm cheating(on the car not my wife).

probear · #2 06-26-2007, 09:16 PM

Well, the AH mechanic that worked on my SDL prior to my ownership apparently had the same initial problem. My A/C drew too much power, so, they upped the fuse. End result, it blew the A/C relay. I'm glad I found the problem prior to blowing any more relays, or worse, but the bottom line is that the A/C clutch was pulling way too much power.
Get the wiring schematic, and first replace the fuses with the right size, one at a time.

You might want to find a wrecked car to try to get the harness off of it. It certainly would be a much easier start.

covertcourier · #3 06-26-2007, 09:37 PM

- The fuses have all been set to the original size. could the a/c still be draining the system despite not being engaged? Or have greater prolems been unleashed?

Thanks-James

probear · #4 06-26-2007, 10:01 PM

First, you need to see if you have any electrical drain with the ignition off. If so, then isolate it. If not, then check the draw with the ignition on and all accessories off.

Describe more about how it is 'eating' batteries.

It sounds like the melted wiring has caused one or more shorts, and the realistic solution is just tracing them down

covertcourier · #5 06-26-2007, 10:17 PM

The mechanic changed the battery and said he could not find a drain on it. After 3 days of starting and stoppng (no long drives) the new battery is dead.
The housing around the wiring harness is off. Viewing the wires i have isolated the a/c line and it is toast. The mechanic by-pasted the a/c wires and still electric abnormalities.

I'll try to send pics in the morning.

I also priced out a new wiring harness at $940 free shipping whoppee.
Finding a wrecked 86 SDL may not be as easy.

thank you -James

dieselmania · #6 06-27-2007, 12:01 AM

Keep looking for a used harness. When my son's 351 Windsor caught fire (alternator) Ford wanted $1,000 for the engine compartment harness and another $400 for the injector harness. We got them both at the salvage yard for $150. I know the SDL is not as common as a Ford but someone will have it.

covertcourier · #7 06-27-2007, 02:54 PM

Posted last night about my wiring harness and a/c, which seems to be toast.

I searched today (while at work) for a junked 1986 sdl. No luck so far. If anyone knows of a 126 sitting around with nothing to do, please let me know.
I'm in Virginia and always looking for an excuse for a mercedes oriented road trip.

Also has anyone switched out a engine wiring harness on a sdl? I helped a friend change his biodegratable wiring harness in a 94 e320. I think the 126 has many more connections.

thanks -James

vstech · #8 06-27-2007, 03:38 PM

I seriously doubt that an 86 SDL would have a MORE complicated wire harness than a 94 e320!
very little electronics compared to the 94 would be my guess.

covertcourier · #9 06-27-2007, 03:47 PM

some pics - the engine sounds great, no rust, just unpredictable electrical problems.

vstech · #10 06-27-2007, 06:48 PM

Oh, my! I see what you mean by scary electrical problems... I like my 82 more and more!

Hit Man X · #11 06-27-2007, 06:51 PM

Just find a good, used harness. Not a big deal.

Bill Ladd · #12 06-27-2007, 07:15 PM

Try Here: Car-Parts

They might be able to find you a harness.

Dervman · #13 06-27-2007, 08:53 PM

When tracing or bypassing your electrical problems, don't forget that the supply for the A/C Compressor Clutch also feeds the Auxilliary Electric Water Pump for the heating system. Both are powered from Fuse #5. On my SDL I had to disconnect the Aux. Pump as even after replacing the fried A/C Clutch the fuse was still blowing. The Aux. pump was seized - a common problem - and was overloading the fuse circuit.

Definitely try to find a replacement wiring harness as otherwise you could be chasing gremlins for many moons to come!!