help - points / contacts inside wiper motor ??????

[eschneider]

OK, this is on a Morgan - but the wiper motor should be similar to something on a TR2/3/4. It is a Lucas single-speed parking type, model DR3A, Lucas 75414B.

Tore the motor down and found a weird contact breaker on the ground side - guessing it is somehow magnetically operated. Hope fully someone here knows its purpose, and can advise if it can be removed and the wire simply grounded like a standard DR3 motor?

A closeup shot is attached below. Other photos can be found at the following links:


https://i62.photobucket.com/albums/h110/schne92650/weird%20wiper%20motor/a-back.jpg

https://i62.photobucket.com/albums/h110/schne92650/weird%20wiper%20motor/a-front.jpg

https://i62.photobucket.com/albums/h110/schne92650/weird%20wiper%20motor/a-front-close.jpg

https://i62.photobucket.com/albums/h110/schne92650/weird%20wiper%20motor/a-removed.jpg

 

[TR3driver]

Does look to be some sort of thermal cutout, not found on the TR motors. Perhaps the wiper mechanism is more prone to jam on a Morgan? At any rate, like most protection devices, you can probably bypass it without ill effect, until it is needed.

If it does become needed, though, chances are that the motor will be ruined even if it doesn't set fire to the rest of the car. Why not clean it up and put it back?

 

[DrEntropy]

Looks to be a bi-metal thermal cut-out. Cleaned, points "dressed" and the thing put back in place would be my route. I haven't seen that in any of the wiper motors we've done, either.

interesting.

 

[dklawson]

I agree with both the Dr. and Randall. Looks like a bi-metal current limit switch. I'd clean it as the Dr. prescribed and put it back into the motor.

 

[eschneider]

Thanks. Part of the problem is that the wiring has been tampered with, and I'm not sure how it's supposed to be wired. In fact, after closer inspection, this switch is currently wired to the constant power terminal (+12V, negative earth) There was another solder connection to the switch that has been snipped. I checked for continuity to ground via where the switch is crimped to the case - no continuity - it is insulated from ground.

I may hand this off to a specialist.

 

[dklawson]

Randall and the Dr. will probably know for sure, but from what I remember the early wiper motors like the DR3A were turned on and off (and changed speeds for multi-speed models) by the dash mounted switch completing the ground path for various windings.

I believe Dan Masters has a couple of documents on the web about wiper motors. You may want to Google for those documents and see if any of them clarify your Morgan's wiper wiring.

 

[DrEntropy]

Yup. Grounding it via the switch is the way it works. Giving this a bit more thought: There ought to be a "lump" or irregularity on the armature to cause that contact to open and break the circuit when it gets to the "park" position, even if the switch is turned off when the arms are in any other place in their travel. It is a mechanical switch, not thermal or magnetic. My bad.

 

[TR3driver]

I 'gree the dash switch works on the ground side (for self-parking variants); but I don't think a park switch could be triggered from the armature. The armature turns many times (and hence goes through the same position) as the blades move across the windscreen. The park switch would also parallel the dash switch, which is inconsistent with having one side wired to the 'hot' terminal.

But it sounds as though it has already been bypassed, so perhaps no further action is required.

 

[eschneider]

Yup. Grounding it via the switch is the way it works. Giving this a bit more thought: There ought to be a "lump" or irregularity on the armature to cause that contact to open and break the circuit when it gets to the "park" position, even if the switch is turned off when the arms are in any other place in their travel. It is a mechanical switch, not thermal or magnetic. My bad.

Yes, the park circuit is also present and accounted for, on the ground side.

yes, this is the type that has parallel grounds through the dash switch and the park ciruit.

The switch pictured is different - it clamps to the inside fo the casing as shown in the photos, and it is (at least currently) soldered to the positive side of the wiper circuit.

 

[DrEntropy]

Yeah, Randall, the armature spins thru too many revs to "park" at the proper spot every time. gah.

I'm a nidiot. Can I have a do-over?