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?

__________________
-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.

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.

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

__________________
14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

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.

__________________
-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.

A wee bit o "funk" in the wiring. Chck for bleed through ( continutity) in wires running together, as the insulation seems to fail.

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.

__________________
Dean

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.

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

Jim

__________________
14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

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.

__________________
-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.

Is there power to the fuse with the lights on?

__________________

Gone to the dark side

- Jeff

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.

__________________
Dean

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.

__________________
-justin

1987 300TD, 1987 300TD
2008 R32, 2000 Passat Wagon

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)

__________________
Dean

Is there anything wrong with the electricals? Anything specific or just wacky generalized functioning? (Electricals is a word to me BTW....)

The lights work and a few other things that the fuses have no power for. As far as corrosion on the contacts that's definitely something I thought of. Also I thought about fuses being bad. That's easy to check, just continuity. But back to the contact corrosion. I placed the ground on the engine and measured voltage on several of the fuses. However the six or so that I don't get a voltage on I scraped the lower terminal (pre fuse) and nothing. So, something weird is going on. I looked further and saw that someone has taped over wire insulation so who knows what's going on.

__________________
-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.