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Old 12-29-2000, 01:16 AM
Richard Wooldridge Richard Wooldridge is offline
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Join Date: Dec 2000
Location: Battle Ground, WA
Posts: 576
Diagnostic plug/tach amp fix

Hello all,

I had the same problem with the diagnostic connector on my '82 300td, and after taking the top cover off and removing some of the potting compound, what I found was that the pins are supposed to be retained by a backup plate that latches onto the bottom via 3 pairs of opposed locking fingers. The plastic fingers had gotten weak and weren't able to hold onto the plate anymore. I fixed it by making some little plastic wedges to go between the fingers to keep the plate latched. The fingers are less than 1/8" apart, so it doesn't take much of a wedge to fix it. Once the pins are properly retained just reassemble the unit and it should work fine. You can make a simple test to determine if this is the problem by pushing on the pins before you take the diagnostic plug apart - the pins should NOT push in at ALL, and should all be out the same distance. Hope this helps! You can see my car, which has a 4.3L Chevy V6 installed, at:

Richard Wooldridge
1982 300TD 4.3L
1974 280C (It's a CLASSIC!)
1977 Jag XJ6L
1977 280Z 2+2
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