I am almost done with a complete wire harness swap from my old 1985 Euro 300TD to my present 1985 300TD. I am doing the swap so that I can add the ABS from my old car and the manual climate control. Almost every wire has a home except this bulb which I can't figure out where it goes. The label I put on it two years ago says : dash light up through column. The pictures I took at the time show it behind the instrument cluster but I do not know where it plugged in. It may be ABS related. Any thoughts?

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1985 Euro 300TD Turbo

I hear that !!!!!!!!

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

Hm. Is that the brake warning light?

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Occasionally, I am able to figure something new out and tonight I caught a break. It turns out this is the light for the charging system. On the federal car this bulb was just in a brown holder screwed into the back of the cluster. It has been working and would illuminate when I turned the key. I pulled that holder and bulb, screwed in the pictured holder and bulb, and when I turned the key it lit up correctly. I am guessing it must feed some sort of signal to the ABS system.

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1985 Euro 300TD Turbo

On a 123 the light for the charging system is integrated into the left pod circuit board. It does not hang on a wire harness. Also there is only one wire going to this bulb, which means the other end finds ground when it is inserted in the cluster assembly. Charge bulb sits between the switched voltage ("terminal 15") and the D+ on the alternator.

I suspect this is the ABS warning light, which will illuminate when the car is on but not running, same behavior as the charge bulb.

Since that bulb is not integrated into the rest of the cluster wiring, that tells me it is probably ABS warning. Only the latest 123s got ABS because it was introduced in the early 80s.

You may need to change out the cluster designation strip from your Euro cluster, to get the "antilock" legend to show up. There is probably an empty hole in the back of your Federal cluster and if you shine a flashlight through from the back you will see the empty space on the legend strip. The designation strip pulls out from a slot in the side.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Thanks for the response. There is another bulb that is the ABS warning bulb. It goes on the other side of the cluster next to the glow indicator. This is the only spot this bulb will fit and it lights correctly for the charging system. It must be a difference specific to the ABS cars. Mine is an '85 300TD

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1985 Euro 300TD Turbo

Interesting.

I would check this just to confirm. Since the charge bulb is essential to the function of the voltage regulator it would be good to make sure you have > 13 V dc at the battery with the engine running. I'd hate to see you end up with no excitation on the alternator and a dead battery in 100 miles.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech