Porsche Repair: 925 washer pump problems, windshield wiper, wipers

Question
Hi Dave,
I've come across a problem with my washer pump on the 924. Pump not working so removed it and checked the voltage at the terminals, hooray 12v when wiper arm pulled in! Made a couple of leads up to the battery and connected pump, hooray pump worked! Reconnected pump onto the terminals and nothing Boo Hoo! All fuses correct and present, earth checked and ok, so somewhat confused, what do you think? Regards Conrad  

Answer
Hi Conrad,

Well, you've certainly checked all the obvious things.  I'm looking at a 1983 wiring diagram (probably only 944 but I'm not sure.  The diagram depicts that the windshield wiper relay also controls the pump motor on a different circuit than the wipers.  Thus, conceivably, the wipers could work but not necessarily the pump.   This assumes the switch is still good.

If it were me I'd check for corrosion/crud in the switch, because the pump relay should last longer than the wiper relay, right?  And a two-function Porsche relay is very expen$ive.

Dave