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  #1  
Old 06-18-2007, 11:29 PM
777funk's Avatar
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Has Anyone had 87 300d Wiring Harness Problems w124

Has anyone had problems with the electrical system on an 87 300dt?

I have one and the fuse box has all kinds of funky things going on. I measure '0' volts on several fuses (5 or 6) and I'm measuring the before the fuse side of the circuit so it's not a bad fuse.

I've heard things about wiring harnesses going bad. How do I start to diagnose? Where do I begin to look?

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-Dodge Ram 12V
-E320 '95 200k
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-300sd '80 300k
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-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.
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  #2  
Old 06-19-2007, 06:12 AM
Gene
 
Join Date: Mar 2007
Location: Buffalo NY
Posts: 1,102
The pre ignition harness goes bad on W124s, not the main engine harness.

I'm not familiar with the engine harness (yet), but check the pins on any bulkhead connectors in the system. Then its simply a matter of tracing each wire.
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  #3  
Old 06-19-2007, 06:18 AM
JimFreeh's Avatar
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Where are you measuring?

Are you measuring on the fuse or on the brass contact?

W124 wiring harness failures are late in the car's production.
You will have wiring problems in a W124 TD, but they will be from bending the harness and will occur at the rear hatch and the doors.....

You can pull up the fuse panel and get to the hard wiring underneath, might be worth having a look see and check for voltage.

Jim
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85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles
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  #4  
Old 06-19-2007, 08:02 AM
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I'm measuring before the fuse (The hot side-Well the side that supposed to be hot). I think I'll be pulling off that pannel and see what's going on underneath. I think there may be some weird things happening though. Because sometimes my instrument cluster pannel illumination works and sometimes not. Also, once in a while my right turn signal blinks fast and sometimes slow. Also, the car dings (The interior dinger/buzzer) while I put it in gear with the door open. Just some weird stuff going on.
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-E300d '99 350k
-Suburban '93 220k
-TDI Jetta '03 350k
Sold
-F250 '96 7.3
-Dodge Ram 12V
-E320 '95 200k
-E320 Wagon 1994 155k
-300d Turbo '87 187k miles
-E320 1994 200k
-300d Turbo '84 245k (sold to Dan62)
-300d Turbo '84 180k
-300sd '80 300k
-7.3 Powerstroke Diesel 15P Van 500k+ miles
-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.
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  #5  
Old 06-19-2007, 08:56 AM
Gene
 
Join Date: Mar 2007
Location: Buffalo NY
Posts: 1,102
A wee bit o "funk" in the wiring. Chck for bleed through ( continutity) in wires running together, as the insulation seems to fail.
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  #6  
Old 06-19-2007, 09:05 AM
deanot442's Avatar
Diesel Dean
 
Join Date: Feb 2004
Location: Canterbury CT
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Quote:
Originally Posted by 777funk View Post
Has anyone had problems with the electrical system on an 87 300dt?

I have one and the fuse box has all kinds of funky things going on. I measure '0' volts on several fuses (5 or 6) and I'm measuring the before the fuse side of the circuit so it's not a bad fuse.

I've heard things about wiring harnesses going bad. How do I start to diagnose? Where do I begin to look?
Do you have the factory tech manual on cd rom? It has all the wiring diagrams and will tell where you should see voltage. The things you are measuring may need the key in the run position or may need to have conditions met to be able to measure any voltage at the fuse. The cd can be a bit pricy but once you use it a few times it becomes priceless (imho) I agree with the fact that the usual places for failure are in the door and lift gate hinge areas.
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  #7  
Old 06-19-2007, 11:30 AM
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Ok I just checked a few of the devices that the fuse pannel has no juce on and I think most of them work. This makes it Really confusing now. For example... the Low and High Beam circuit has no voltage at the hot side of the fuse. But... they both work??? What in the world???
__________________
-E300d '99 350k
-Suburban '93 220k
-TDI Jetta '03 350k
Sold
-F250 '96 7.3
-Dodge Ram 12V
-E320 '95 200k
-E320 Wagon 1994 155k
-300d Turbo '87 187k miles
-E320 1994 200k
-300d Turbo '84 245k (sold to Dan62)
-300d Turbo '84 180k
-300sd '80 300k
-7.3 Powerstroke Diesel 15P Van 500k+ miles
-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.
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  #8  
Old 06-19-2007, 11:43 AM
JimFreeh's Avatar
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Maybe it's the ground....

....that you are using when you check for voltage with a meter.

Jim
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14 E250 BlueTEC black. 45k miles
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94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles
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  #9  
Old 06-19-2007, 11:59 AM
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I don't think so. I used the engine as a ground. Also, if I didn't have a ground I wouldn't be reading voltages on other points in the fuse box. So I think that is ruled out. I do actually get readings on most of the fuses. But there are about 6 or so that have no voltage.

Quote:
Originally Posted by JimFreeh View Post
....that you are using when you check for voltage with a meter.

Jim
__________________
-E300d '99 350k
-Suburban '93 220k
-TDI Jetta '03 350k
Sold
-F250 '96 7.3
-Dodge Ram 12V
-E320 '95 200k
-E320 Wagon 1994 155k
-300d Turbo '87 187k miles
-E320 1994 200k
-300d Turbo '84 245k (sold to Dan62)
-300d Turbo '84 180k
-300sd '80 300k
-7.3 Powerstroke Diesel 15P Van 500k+ miles
-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.
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  #10  
Old 06-19-2007, 01:51 PM
babymog's Avatar
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Is there power to the fuse with the lights on?
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  #11  
Old 06-19-2007, 05:55 PM
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Diesel Dean
 
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might I suggest using the neg terminal on the batt for ground, or a bare spot on the chassis. I have found those to be the best.
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  #12  
Old 06-19-2007, 05:59 PM
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those fuses seem notorious for getting corroded due to their placement, which will cause them to not conduct even though they may appear in good condition.

when in doubt, replace the fuses. should be step one in troubleshooting an electrical issue on a 124.
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  #13  
Old 06-19-2007, 06:12 PM
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Diesel Dean
 
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in the past i have twisted the fuse in its socket and been able to regain operation of whaatever the fuse was protecting (at least for a little while)
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  #14  
Old 06-19-2007, 06:19 PM
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Is there anything wrong with the electricals? Anything specific or just wacky generalized functioning? (Electricals is a word to me BTW....)
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  #15  
Old 06-19-2007, 07:25 PM
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Dieseldiehard
 
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Forget the meter.
I suggest using a small lamp, like a turn signal bulb, as the indicator, it loads the circuit in case there is a high resistance it won't light while a voltmeter will and give a faulty reading. Solder a long set of leads to a small 12V bulb then connect one end to the chassis, the neg terminal on the battery is fine but way across to the other side of the car. I usually find a screw and stick the ground lead under it and anchor it down. Then turn on the ignition and the headlights and touch each of the fuse clips across the hot side of the fuses one by one.
You should get an indication on every one, then go down the other side, the load side and they should also light up the bulb.
You could have a problem under the fuse block where the terminals are daisy-chained together, there are screws under there but I've never heard of them getting loose (there's a first time for everything I suppose)
If your fuses are not the late version that are godlish colored, then replace them all, the whole set is cheap if bought from the right place. The first thing I do when I suspect fuse problems is replace the lot!
If you still have problems give us the fuse #'s

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