Recently the yellow light on my dash (brake pad indicator - I think) came on. Brake fluid resorvoir is full, took all 4 wheels off and pads are good. Replaced master cylinder about 10K ago. Brakes work OK, maybe a little stiff, but maybe I'm just imagining that. Any ideas?

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John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln

John,
You could try disconnecting the level indicator probe & see if the light goes out, otherwise trial & error disconnecting each pad sensor until you find a bad one.

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Maybe a bad sensor at the pads? I don't know how that would be creating a ground though for the lights to turn on.

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-Typos courtesy of my mobile phone.

^ Agreed, also inspect the wiring harness that leads up through the fender.

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83 SD

84 CD

A wire is grounding somewhere.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

AFAIK only the front brakes have wear sensors.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

+2 on the wiring harness and check the sensor wires themselves.

I didn't tuck the wires in well enough when I replaced them once and they rubbed the inside of the wheel.

I also found the main lines through the fender to be cracked to the conductor on both sides recently. Easily replaced and look nice and clean.

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'85 300TD "Puff The Magic Wagon" - Rolling Resto
'19 Mazda CX-9 Signature - Wife's sled
'21 Morgan 3-Wheeler P101 Edition
'95 E300d - SOLD
'84 300TD "Brown Betty" - Miss this one
'81 240D "China Baby" - Farm grocery getter

Thanks for the insight. As I interpret these replies, I gather that it must be simply a wire making contact and not some major brake component about to fail. Given that avenue of though, I will simply interrupt the current path and not have a sensor light. I check my pads often enough to not feel a need for an idiot light. Again, thanks for the help.

__________________
John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln

Yeah, if your pads are good, no problem. It's just a warning device for the front pads only.

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83 SD

84 CD

http://www.peachparts.com/Wikka/W123BrakeWarningLights

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car