On the earlier 124s one of the three command wires leading to the pneumatic pump splices mid-line to the alarm module, and the 30 circuit to the pump and other consumer elements. Those splices are under the carpet in the cable tray behind the front passenger. The splice are crimped with an aluminium sleeve. If a splice gets wet, as often happens and goes unnoticed under the carpet, the dissimilar copper wire and aluminium sleeve can corrode through the insulation and facilitate a sporadic short circuit.

Here are some pictures from my 1987 300TD which experienced this problem.





I hope this helps.

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http://i284.photobucket.com/albums/l...aman/Fleet.jpg

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