Hello Yak and thanks for the input!

Yes, when the fuse blows the instrument cluster gauges all fail as expected.

I just disconnected the cruise control switch on the column.

I removed the instrument cluster and diddn't see anything there but I completely disconnected it.

I topped off the brake fluid as suggested. the little rubber covers on top of what I guess are the two sensors are all cracked and split but the fluid level is good.

Then I took it out for a spin and some hard braking and the fuse blew again.

I disconnected the brake fluid level sensors.

I disconnected the front brake pad wear sensors.

I disconnected the warning light flasher switch.

Drove around and the fuse blew again! Seems like we are running out of options.

I looked in The FSM but really tell where the TDC Amp is to disconnect.

How does one know if a TDC amplifier is malfunctioning?

How does one know if a brake sensor is malfunctioning?

How does one know if the sensors on the brake fluid are malfunctioning?

Seems like we are running out of options?? Could it possibly be the brake light switch? I kind of thought we ruled it out earlier but I'm just wondering.

See that little number C107 on/next to the wire paths? That means "connector" between the lengths of wire. That's useful info if troubleshooting. In the back of the electric section of the manual it tells you where those connections are located, with [crappy] pics.

You can also go backwards, "I've got a 14-pin connector in the LH footwell...what's it for?" but it helps if the FSM is correct. In the case of the windows, it's not and IDs that as a 6 pin in the back.

Well...if they cause the fuse to blow, they might be malfunctioning. Sorry.

I assume the TDC is for the tach. On the page where the diagram is, it says for locations go to 217. So you go to 217 in the manual, and it says "TDC Amp...in cap of diagnostic connector...202-2" so you go to page 202, look at pic 2. It shows a pic of the left side of the engine.

I think the diagnostic connector is the round screw cap. I never had any call to mess with it. The book says the amp is in the cap.

I'm running out of ideas to suggest. If it's speed/motion/rpm related, then that may be a loose or chafed wire somewhere on the F12 branch. Since the F12 is the switched fuse, it's possible that someone hacked into it for a aftermarket radio or something.

Crazy question:

Has the brake light wiring been mucked with? any of the wires damaged? On some cars I've seen, the tail-light wiring passes under the side plastic panels in the trunk. Maybe one of yours is getting wet somehow, or maybe the wires have been crushed? Something to check.

__________________
My first Mercedes Benz. 4/6/07.

1984 190E (201 024) 2.3L four.

I have a progress report. First, thanks to all for the ideas and input so far. The process has taught me alot and has been very helpful. I had to leave for a week and I'm ready to get back into it. I refuse to let this thing win!!

I tried to get the fuse to blow by making a abrupt stop with the ebrake and could not. So then I unplugged the brake switch at the brake pedal and could not get the fuse to blow. With this and all the other tests and observations I have concluded that the problem has to be in the brake switch itself or a damaged wire going to the tail lights.

I took the tail light assemblies apart again and made absolutely sure there is nothing causing the problem there.

Any ideas where I would start to look for problem wires? The trunk section is fairly easy to access and the places under the dash are easily accessible with it taken apart the way it is now. But after that would I need to remove seats, carpet etc.? Do the wires to the tail lights run all inside the car?

Any words of wisdom on this next undertaking?? Thanks again to all!!!

Craig

Since it appears to be speed and/or motion related, I'd look at places that get pinched or move. Because it isn't replicated by using the brakes when not moving, I wouldn't place all the eggs in the brake circuit basket, but you've got to start somewhere.

I'd trace back from the brake lights. Look for where the harness goes under the sheet metal panel near the fuel tank. Look for where it passes under the seat. If there's a place where it flexes, maybe it's chafed inside.

Or start at the fuse box and go downstream.

Carpet and seats are easy to remove.

Like I said in reply #65, the wires to the tail lights pass UNDER the two side pockets in the trunk. I've seen 2 cars, a 190D and a 300SD that had issues with the wires being chafed. The side panel just pulls out in one piece. Easy check.

__________________
My first Mercedes Benz. 4/6/07.

1984 190E (201 024) 2.3L four.

Hello Holmesuser01 and Yak, I pulled the trunk panels out and looked at all the wiring in the trunk and there is no obvious signs. I took the rear seat out and didn't see anything there either. Tomorrow I take the front seat and carpet out and have a look. If I don't find anything I think I'll string some temp wires to the lights and see if I can learn anything. Just seems like it has to be from the brake pedal back because it won't blow the fuse with the brake switch disconnected. But what do I know!! Thanks for the input.

I dont believe its your brake lights. I also dont have any other ideas at the moment.

When your brake lights are active they draw about 5 amps total or more if you have other lights wired in (fog light brake mod). Which is more than 50% of the 8 Amp fuse's capacity.

That leaves 3 amps left to whatever else is on the circuit. 3 amps for all the normal mercedes things. Now if something is amiss and is drawing more than 3 amps, when you add that extra 5 amp load, its going to pop the 8 amp fuse.

If you apply the brakes while parked and they don't blow the fuse then I don't think there's anything wrong with the wiring for them as none of that moves during transit.


I'll look back at the FSM and see if I can see anything else.

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

FSM Lists:

Stoplights
Cruise Control
Warning Indicators
Gauges
Turn Signal Lights
Warning System

Have you checked out your turn signal lights? What about the turn signal switch itself? Does yours function fully?

If you were adventurous, you could connect up the meter to the fuse as we did previously and drive the car around and see what happens. I suppose you could also jack up the rear end of the car, safely secure it and "drive" that way. Aside from bumps that would be pretty much the same...

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

Hi JamesDean,

Well, I believe it's not the turnsignal switch because I disconnected the combination switch at the steering column. It was one of my original suspects because it was replaced a few years ago and every now and then the wipers would come on and make one swipe.

Last week I was driving the thing around with all of that FSM list disconnected. Literally the instrument cluster out, cruise control disconnected, warning stuff disconnected, brake sensors and brake fluid sensors disconnected. Almost like everything disconnected and still be able to start the car!

Then my last thing was, I disconnected the power to the brake light switch and could not get the fuse to blow.

Also, keep in mind not only does it blow an 8 amp it blows the 16 amp.

The FSM shows a wire going to the Cruise Control Amplifier and a wire going to the Cruise Control Actuator. But if a guy has both of those disconnected you would think they would not be part of the issue.

Then all there is from the brake light switch is the brake light switch itself and the lines to the brake light assemblies.

I'll take your input and do some more stuff today. It would be interesting to see if it would blow the fuse with the back jacked up. Because it does seem like it needed that forward momentum coming to an abrupt stop to make it blow.


Onward I go! You have shown me that I can always convert it to a recliner!!

I'm keeping my fingers crossed for you. Electrical problems can be misery to find.

__________________
My first Mercedes Benz. 4/6/07.

1984 190E (201 024) 2.3L four.