I removed it to transfer the speedo to the plastic housing attached to the quad gauge. If there's an easier way to add a quad gauge to an 87 300D it can't be a lot easier

Jeremy, from observation I thought the rheostat was soldered to the board. I didn't try to pry it off. I have a spare I can practice on. I'll check resistance and use the one with lower resistance at the brightest setting.

Sixto
87 300D

Ah, that explains it. The rheostat is not soldered on... it will simply pull off once you remove the screw, allowing the white plastic speedo housing to separate from the quad gauge pod. The three main pods do interlock, though, which is a real nuisance!

Which reminds me, I have one of these "quad" pods with vacuum reading that I'd be willing to sell fairly cheap. I had thought about doing this mod several years ago, but ended up mounting an AutoMeter gauge on the dash instead (0-35psi).

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Dave
Boise, ID
Check out my website photos, documents, and movies!

To remove just the rheostat, you need remove only one screw. To make room for prying, you can also remove the "low coolant" warning lamp. Not necessary but helps. (first picture)

Pry gently with a couple of small screwdrivers. The rheostat fits so tightly you'd swear it was soldered/welded/glued on but yes, it comes off. (second picture)

With the one screw out, the only thing holding the rheostat to the pc board are the two plugs. Once pried loose, the rheostat just lifts off. I drew red lines to show how the rheostat goes onto the pins in the pc board. (third picture)

That's all there is to it.

Jeremy

Attached Thumbnails

     

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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
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Great explanation & photos, Jeremy! One tip for re-assembly: The shaft of the rheostat is keyed to the plastic knob. When pressing it back into place, it should not require excess force. If it doesn't want to go back together, gently rotate the plastic knob, you can feel when it lines up with the shaft, then the rheostat will easily press on all the way.

I just picked up a 4 gauge cluster for my W126 to do this mod.


EDIT: It appears that the W126 gauge pod requires modification to work in a diesel. Specifically a pin added to the #13 location to operate the glow plug light.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine