Windscreen Wash Pump - electrical resistance problem?

[wonkey]

I have a 2001 VW Passat 1.9TDI Estate. Few months back the front windscreen wash appeared to fail, slowly getting worse until no water was pumped. I assumed the pump had died, so bought a replacement.

New pump fitted, exactly the same problem. The rear wash works fine, same pump, you can hear it running. Front wash, activates wipers, no water. Tried switching over the outlet connectors on the pump and using the rear wash switch I could get water pumping out of the front washer jets, so no blockage.

Put the old pump back in and exactly the same as above - that'll teach me for not testing properly before buying a new pump!

Old and new pump tested externally and both can pump water in either direction without a problem.

To the electrics, about 11.7v reaching the pump. Resistance of about 0.3 ohm on one switch, but 1.3 ohm for the other. Looks like a potential culprit, corroded terminal or earth? Can anyone point me in the direction of potential connectors and/or earth locations? Traced the pump connector directly to the panel in the passenger footwell. As it's an estate (has front/rear wash) I found the wiring diagrams a little confusing, although it seems some potential earth points may even be at the rear of the car Any advice gratefully received!

Final point - rear wash tubing (about 6" away from pump) has a small slit in it, which causes it to leak slightly. The tubing tends to touch the electrical wire allowing water to run down to the pump connector. I pretty much never use the rear wash (although I think it has to work to pass the MOT), but checked the connector and couldn't see any sign of corrosion. Connector appears to have a rubber seal within, is it possible there is corrosion behind it?

[martin1810]

You have identified the most likely fault yourself. High resistance. You just have to find it. It will normally be on the earth side but if water has got in a connector it can be the connector.
You just have to follow the wires. Great fun. Not.