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  #1  
Old 03-21-2006, 08:20 PM
1badav's Avatar
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Location: SE WISCONSIN
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Electrical Issues........1986 300SDL

Since acquiring my 300SDL in January I have tackled many of the electrical gremlims I inherited, but I am stumped by these three.

1)When I switch on the right-side parking light the headlights also come on, but this doesn't happen when I switch on the left-side parking light.

2)My front power seat switches on both driver and passenger sides only operate when the lower of the two door contact pins are extended(door open position). When the pin is compressed by the door being closed--- no switch functions.

3)I have a high pitched, and very intermittent warning buzzer which sounds under the driver side dash. If I rock back very hard against the driver side seat back and roll around on the seat itself for awhile(this is almost sounding pornographic!) I can sometimes get the buzzer to stop---but only so infrequently that I can't really attribute the silencing of the buzzer to the action taken.

I have replaced fuses, the battery, fixed the trunk hinge wiring, re-wired the aftermarket Blaupunkt radio with home run shots and by passed the fader, fixed the power antenna which was frozen in the upright position, but I just can't get a handle on these.

Your assistance would be greatly appreciated.

Please be as simplistic as you can in describing potential remedies or isolation of problem techniques as I am a relative novice to electrical work.

Thanks in advance.

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1986 300SDL
1988 Monte Carlo SS
2002 Avalanche
2003 100th Anniversary H-D Dyna Wide Glide
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  #2  
Old 03-21-2006, 08:31 PM
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buzzer

I'm electrically clueless myself. The only one I *might* be able to help you with is the buzzer. Switch your headlights on, remove the key from the ignition and exit the vehicle. If the same buzzer sounds it's your headlight on warning buzzer. And I'd suspect a contact short in the wiring under the dash for it which might be affected by your pornographic exploits on the seat. That is to say when exerting yourself in the seat... you might be moving the vehicle just enough to cause the slightest movement of the wiring to the buzzer which then breaks the short or makes it happen again. Some cars apparently also have a seatbelt unhooked warning buzzer. If that's what it is a similar test with the seatbelts unfastened might show that up.

- Peter.
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  #3  
Old 03-21-2006, 08:36 PM
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try this

http://mb.braingears.com/126_DISC1/program/ETM_300SDL.htm

electrical troubleshooting manual. Also, get a meter. Sounds like theres power where there shouldn't be, and vise versa...

I have similar issues but, ignore them unless its a bother or, I find myself grinding and gyrating into my seat

Hows your engine lower end power? (unrelated question)
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  #4  
Old 03-21-2006, 08:41 PM
1986 300sdl 1985 380se
 
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Location: West Monroe LA
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I have a 1986 300sdl that had some pretty strange electrical problems when I first purchased it. Specifically, the power door locks did not work, and the exit light under the doors did not operate and the fasten seat belt light kept staying on . I found that the drivers side rear exit light shorted out and blew the fuse. When I replaced the little light assembly under the drivers side rear door and replaced the fuse, my exit lights all worked under the doors and my power door locks now worked. BUT my fatsen seat belt light would continually flash, and the main inside light by the sunroof would not turn on when you opened the drivers side door, but it would with the passenger side door. Also my seat memory buttons would not operate unless the doors were closed.
I have the factory manual for electrics and studied and studied the wiring diagrams and decided that the interior light by the sunroof panel was bad. I found a nice one on e-bay installed it and still had the same problem. Also I then realized that when I started the car with the seat belt off, no warning buzzer. Also no warning buzzer when I left the headlights on and turned off the car and opened the drivers door. I then looked under the dash on the drivers side and found the SEATBELT WARNING RELAY. It sits on a Bracket just above your feet. It is bolted to the Cruise Control Unit. I took it off and opened it and found a bad solder trail on the circuit board. In fact it had melted. I traced the circuit board functions using the service manual and decided I needed a new one. WOW, they are expensive. I then bypassed the actual circuit on the board with a jumper wire I soldered between the two connections. I plugged it in and guess what????

When I open the drivers door my interior light comes on. When I put the key in the ignition, the warning buzzer sounds until I buckle my belt. When I leave the headlights on and turn off the car and open the door, a buzzer sounds. And Now my seats work from the memory button with the doors open.

I looked at the wiring diagram again and realized this probably all happened from the shorting out of the rear exit light.

I re-installed the relay and all is well 9 months later with no problems. I keep looking for a wrecked 300sdl to see if I can find another relay as a spare, or another one that has not been damaged, but no luck yet.
This may be the cause of all of your problems.
Good Luck and keep us posted.
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  #5  
Old 03-22-2006, 11:13 PM
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Okay, update finds nothing out the ordinary with regard to the operation of the warning buzzer for when headlights are left on and the car's door is opened.

Seat belt warning buzzer activates when door is open and driver's seat is occupied only if foot is applied to brake. Buzzer then sounds for a few seconds and then goes silent. Position of seat belt, either attached or retracted seems to have no effect on this.

I have had somewhat similar issues as you branlj with seat belt warning lamp light flashing continuously for extended periods of time(like the 12 hour drive from PA back to WI when I picked up the vehicle) and several other periods, but it seems to come and go so I have nothing to pin the behavior to.

That particular gremlin hasn't surfaced recently. I disconnected the alarm system recently, but I have fixed and altered so many minor electrical things during the last few weeks that I don't know to what I can attribute the success of correcting that problem, if it is indeed corrected.

I did notice however, if that warning device under the driver side dash is shaken when it is sounding, it will go silent almost immediately.
I ordered a new one from the stealership today for $66.00 and I'm going to see if that corrects anything---if that is indeed the part you were referring to having performed surgery on.

Hernando5w126-- thanks for the braingears link, I found that one a few weeks ago---of course after I spent the money on the cd from MB! Not unhappy I bought it though, it was only $20.00.
Wife says my engine's lower end power has never been better!
Seriously though, if you're defining low end power as pick up, I don't have enough experience with the car or any diesel experience prior to owning this one to gauge or compare it to. From everything I've read here in the Forum, I've got what everyone else has----a diesel. Until the turbo kicks in, it's a dog, a lovable dog, but a dog none-the-less if you're comparing it to a gasser.
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1988 Monte Carlo SS
2002 Avalanche
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  #6  
Old 02-28-2008, 09:07 PM
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I would suspect the wiring that goes into/out of the door, this wiring tends to short or break completely because it flexes each time you open/close the door. I fixed a problem like this (interior lights would not go out) by cutting a wire for the door lamp inside the car. Another time I fixed the license plate lamps by cutting out the bad section of wire and replacing it (this broke from the trunk opening/closing, again the flexing tends to break stuff).
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  #7  
Old 02-28-2008, 10:16 PM
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Quote:
Originally Posted by 1badav View Post
Since acquiring my 300SDL in January I have tackled many of the electrical gremlims I inherited, but I am stumped by these three.

1)When I switch on the right-side parking light the headlights also come on, but this doesn't happen when I switch on the left-side parking light.

2)My front power seat switches on both driver and passenger sides only operate when the lower of the two door contact pins are extended(door open position). When the pin is compressed by the door being closed--- no switch functions.

3)I have a high pitched, and very intermittent warning buzzer which sounds under the driver side dash. If I rock back very hard against the driver side seat back and roll around on the seat itself for awhile(this is almost sounding pornographic!) I can sometimes get the buzzer to stop---but only so infrequently that I can't really attribute the silencing of the buzzer to the action taken.
1) It's got some fairly complicated circuitry for the headlamps and it all goes via the exterior lamp failure monitoring unit. This device is inside the fuse box and all power to and from the headlights/taillights/markers goes through this device. I'd bet that the problem originates in this unit.

2) The seats operate when the door is open. This is normal. If you close the door, the keyswitch needs to be in the #2 position to operate the seats.

3) How long does the buzzer operate? The seat belt buzzer operates for about 10 seconds after you turn the key to the #2 position. You can silence the buzzer by pulling the connector (a single two wire connector........all by iteself) underneath the driver's seat.

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