Two Speed Wiper Issue

[Darren Groves]

Since I got the Spitfire back on the road last year, I've been struggling with the wipers. 

Brand new wiper motor, home made loom and this circuit has its own fuse. Initially all worked fine. 

Symptoms were that I'd lose low speed, high speed would be fine but they also wouldn't park. Or sometimes the fuse would blow. 

If I pulled the connector from the park switch squirted with WD40 or electrical contact cleaner and it would start working again. 

 By wiggling the park switch I can recreate anything from them working correctly to the symptoms above, so assumed this was the issue and bought a replacement. I fitted that today and I get both speeds working fine, no blowing fuses, but the wipers won't turn off.... 

Any ideas? Two Park switches with different faults maybe? 

 

[Josef]

Could the park circuit be shorting inside the case? Just a guess as it’s been a while since I had one of the Spit MkIV style ones apart and can’t picture quite what they’re like!

[chrishawley]

Is your motor a 14W (round body) or DR3 (square)? And dash mounted switch/washer pump?

But your situation is a real puzzle. But I'll have a punt at a couple of ideas to see if they stimulate any other, better, thoughts.

One culprit for erratic wiper faults is the five-pin block connector at the motor. The quality of reproduction items can be truly appalling and the females just don't grip the male spades well enough for reliable connections. But that wouldn't easily explain a not-stopping motor.

A weak earth (black wire) might be a possibility since in order to stop dead both sides of the motor have to be shorted to earth. Without a dead stop the gear wheel could over-run the stop position and keep going round. How likely? Not all that much.

The dash rotary switch itself may be a culprit. Never had one of these apart myself but on experience of similar ones it's perfectly possible after 5 decades that the tracks and contacts are heavily deteriorated.

Not sure there's any answer here, but maybe it'll get some thought going.

 

 

[Nigel Clark]

I've had a similar problem with the 14W wiper motor on my GT6, reluctance for the park circuit to operate consistently.

Attention to the wiring, a new park switch and multiple head scratching sessions never solved the problem. I gave up in frustration and fitted another motor I had on the shelf.... Problem solved.

Nigel

[NonMember]

10 hours ago, chrishawley said:

A weak earth (black wire) might be a possibility since in order to stop dead both sides of the motor have to be shorted to earth. Without a dead stop the gear wheel could over-run the stop position and keep going round. How likely? Not all that much.

It may not seem likely but I have experienced it. Only applies to the 14W motors, though.

[Darren Groves]

Thanks for the replies above, I haven't had much of a chance to look at the issue. Since I posted the above I had just wired the main switch direct to the motor and bypassing the park switch, the motor then worked fine (apart from it won't park of course), so I know the main switch and the actual motor are fine.

I have tried 3 new park switches all from different suppliers, they all give the same result which is I cannot turn off the wipers. 

With the last park switch I bought I just used it as a connector, so not connected to the wiper motor body, by doing this I can manual depress the pin and the wipers stop immediately. So the park switch is doing what it's supposed to but just not when it's in position. So the problem is that the either the pin on the park switch is marginally too short and/or the lobe on the gear needs to be marginally higher so the when the two meet the pin is raised high enough to earth the brush and stop the motor. I have measured the length of the pin and how recessed the lobe is and that tells me they are only just touching, but not enough to depress the pin adequately.

The wiper drive gear was new a couple of years ago and has had a minimal use, there's no sign of wear on the lobe so I see little point replacing that and clearly all the park switches are the same, so the only solution I can see is to find a way of elongating the pin on the park switch or raising the height of the lobe on the drive gear. If anyone has any ideas on how to do either I'd be very grateful.

Thanks.