Electrical failures are often difficult to find, often mass problems are the cause of all misery, especially with a 6 volt current circuit.
Make sure that all ground points are free of oxidation and that the fastening points make good contact.
In our VW models, the ground is obtained directly from the battery terminal which is mounted on the chassis by means of a ground cable. Between the gearbox and the chassis there is also an extra grounding strip which ensures that the engine is grounded properly.
The gearbox is mounted in rubbers with the disadvantage that these rubbers ensure that the engine and gearbox are fully or partially insulated, the extra ground strip breaks through this. This strip is located on the side of the gearbox (at the height of the gear selector) and is mounted on the chassis.
Regularly check the condition of the grounding strip and replace it in case of oxidation or damage.
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