wiper system shorts in high speed mode

[SASV66]

Hello,

I have read a lot of the wiper threads but have not seen this one so hoping someone can point me in the right direction.
I all of a sudden started getting a short (blown fuses) when using the wipers. I hadn't made any wiring changes and assumed from other threads it was overloading due to hardened grease. I removed the rack system and disassembled, cleaned and regreased it. I did a simple test of powering it up direct from the battery to make sure it runs. I did not test both speeds. I reinstalled and reconnected it and it runs in slow but when I switch it to high speed it blows the fuses (both). I tried another known good switch with the same result. I would really like it to work correctly but am at a loss of where to trouble shoot next.
Is it likely a wiring issue, a shorted winding in the motor or something else? Any suggestions are much appreciated. '66 SV

 

[hartmandm]

WSM 145 manual pages 11 & 12 has background on the wiper motor: http://sunbeamalpine.org/wp-content/uploads/2017/10/15-Electrical-System-N-2.pdf

Sounds like you ruled out a defective switch. Maybe there is an internal short on the high speed circuit. You could check the resistance between the wires. Disconnect the 3 wires on the motor and check the resistance between Green and Red + Light Green. I'm not sure what the resistance should be, but I assume it shouldn't be less than an ohm.

Mike

 

[SASV66]

Thanks, Mike. I'll check that resistance.

If it appears to be an internal short I have two follow up quesitons:
1. Correct to assume I have have it serviced by a local motor shop?
2. From other posts it does not appear possible to just wiring without the High Speed in the circuit and still have full functionality, such as parking. Am I correct there?

 

[Scotty]

Thanks, Mike. I'll check that resistance.

If it appears to be an internal short I have two follow up quesitons:
1. Correct to assume I have have it serviced by a local motor shop?
2. From other posts it does not appear possible to just wiring without the High Speed in the circuit and still have full functionality, such as parking. Am I correct there?

I've had only high-speed working before I fixed the wiring and it parked just fine. Your mileage may vary depending on what exactly the cause of your problem is. FWIW my main problem was a bad toggle switch. Good luck!

 

[Acollin]

Are you aware of any other electrical things not working— brake lights, horn etc.?
Andrew

 

[SASV66]

@Acollin Most of the electrical systems work fine but there are some electrical/wiring issues for sure. Lights, horn, gauges mostly work fine. Temp gauged is currently not working. Heater blower wiring needs TLC and I'll be looking at that next. Now that I have the schematic from the chapter of the workshop manual Mike sent the link too (I was confused why the wiper motor wiring is not on the main wiring diagram) I can more confidently troubleshoot the wiring, NOT one of my strengths!!!

Are you suggesting that it is hard to say and may just be tied to other wiring issues?
Much appreciated!

 

[Scotty]

@Acollin Most of the electrical systems work fine but there are some electrical/wiring issues for sure. Lights, horn, gauges mostly work fine. Temp gauged is currently not working. Heater blower wiring needs TLC and I'll be looking at that next. Now that I have the schematic from the chapter of the workshop manual Mike sent the link too (I was confused why the wiper motor wiring is not on the main wiring diagram) I can more confidently troubleshoot the wiring, NOT one of my strengths!!!

Are you suggesting that it is hard to say and may just be tied to other wiring issues?
Much appreciated!

A lot of issues I have had on my car came down to bad grounds. The British seemed to like to be cute with some of that *glares at the turn signal housings*

If your wiring is really damaged and/or been cut up, you might want to consider just rewriting the car, then you know what you got and you’ll have ‘touched’ everything. It sounds like a lot but it’d save you time, ask me how I know lol.

 

[hartmandm]

If it appears to be an internal short I have two follow up quesitons:
1. Correct to assume I have have it serviced by a local motor shop?
2. From other posts it does not appear possible to just wiring without the High Speed in the circuit and still have full functionality, such as parking. Am I correct there?

I have no idea if a local shop could fix the wiper motor. Maybe they could. Maybe they do some damage trying. I'd look for a shop that knows how to service these motors. Hopefully some forum members here will indicate if they know a shop that is good at servicing these old motors.

The high speed gets engaged by the panel switch grounding the RLG wire. So if you left the RLG wire disconnected (and insulate it to prevent an accidental short), you should have just low speed mode and it should not impact the parking feature.

Mike

 

[Acollin]

To sasv66: In a word “yes” is what I am suggesting. My belief, based on little knowledge and a lot of logic and luck, that there is a fault of some kind along your “ green“ wire circuit. While Scotty may be onto something by considering “grounding” given you are also blowing fuses, I might guess it is a wire grounding that is not supposed to be grounded— making body contact Or contact with another grounding wire. Also the green wire runs all through your car making many stops with a number of junctions making it likely to have been messed with or knocked out of place.

My thinking and how I would proceed
1) a fault in the wiper motor is always possible but in my view not likely as the motor is little used and not often messed with. It would almost be like taking a new working part off a shelf after long term storage. Also it sounds as if you have cleaned up the wiper motor and the fault occurred both before and after ( not compacted grease). While it was not part of your test, it is also reasonable to assume, if you had done the battery direct to motor test, both speeds would have engaged Bypassing switching circuits and the green wire. It also occurs to me that doing the direct battery test to the wiper motor as it is back in the car would not be that hard.
2) it seems to me as if you have eliminated the fault being in the switch as you tried a known switch and got the same result.
That leaves to my mind the sequencing of the green wires.

i asked about other electrical bits that were not working and this is were I would focus my search noting all green wire connections. The problem could also be in components connected by green wires.

All that said these are tough problems, but the good news is there is a strict logic to all things electric But can be very hard to find and not always obvious. I know that what I have said is inconclusive but hopefully it gives you some places to hunt.
Also if you still believe the wiper motor is your problem, I would contact Mark— volvoguy and see if he has one he could test and sell it to you.
Good hunting
Andrew

 

[hartmandm]

The green wire supplies current for both low speed and high speed wiper modes. It also supplies current to many other things. I'd expect a fault in that green wire circuit to blow the fuse at other times, not just when engaging the high speed wiper mode. I'd focus on the wiper motor first.

Mike

 

[Acollin]

I see what you are saying, Mike— makes sense.
what would happen if he were to disconnect the wiper motor from the green wire circuit and connect a 12volt jumper wire (battery direct) to the green wire terminal on the wiper motor?

 

[Acollin]

Are you saying that there would be no high speed wiper and there would be the low speed wiper?

 

[BEpine]

To test the wiper motor, (these are the wires from the wiper motor)

The ground wire goes to negative 12 volts.

Green goes to positive 12 volts.

Red/green and ground wire together gives high speed.

Red/green and brown/green and ground wire together gives low speed.

 

[hartmandm]

BEpine is right. I misread the circuit that both wires are grounded for low speed operation. Since you have low speed operation, my theory of an internal wiring short seems less likely. I'd still start by checking resistances between wires.

Mike

 

[SASV66]

I just gotta say, I love this forum! You are all great, thank you so much for chiming in!

I'll be starting with the resistance check and both speeds test per BEpine. Cheers!

 

[sunalp]

The wiper motor isn't grounded. The small black ground wire is for the park function. The
motor has power to it at all times the key is switched on. The motor grounds through the switch,
that's why the wiper switch has a ground wire, usually connected to the back of the tach. As stated above
the wires ground at the switch to give the two speeds

 

[Acollin]

To sasv66
Probably an unnecessary reminder, but if you decide to run the wiper motor check, it would be a good idea to get the wiper blades off your windscreen.
I hope I am not overstepping a boundary, but I’d probably not consider the unnecessary drag and would appreciate the nudge.
Good hunting
Andrew

 

[Tom H]

It's highly unlikely that there is a problem in the motor. The fact that the low speed works pretty much tells you that there is no problem with the windings or armature. Something is mis wired.

I assume you have the green wire connected to +12 V and it does not go to the switch at all. Be sure the green wire does not go to the switch.

I have a spare dash w switches still on it. The switch has terminals labelled 1,4,6, 7, and 8. The wiring diagram shows wires connected to terminals 1,4, and 6, with Ground wire to 6, Red/GRN wire to 1, and Brn/Grn wire to 4.

The numbers are tiny and hard to read. Double check .

Quick test: Disconnect the Brn/ Grn wire from the switch. The wiper should run in low speed at either switch setting (except OF)
While running in slow speed, (in either switch position) connect the Bron/ Grn wire to a ground. Wiper should go faster.

Tom

EDIT: You say you did not make any wiring changes. But you did disconnect the wires when you cleaned and tested it. Is it possible that when you reinstalled it, that you accidentally swapped the terminals where the BRN/GRN and RED / GRN wires are connected? If so, in the low speed switch position, both wires would be grounded, as required for low speed operation. BUT when switched to High speed mode only the wrong wire would still be grounded. Only the Field winding would be grounded, and thus powered, while no power is applied to the armature. It's been a while since I've studied motors, but it seems this might result in excess current through the Field winding, similar to what happens when a motor is stalled.

 

[Tom H]

Just a note to bump this up to the top so SASV6 will see my latest edit. I think that may be the answer he needs.

 

[SASV66]

Thanks Tom. Appreciate the follow up. I have not had a chance to further investigate as the car is not at home with me. I hope to troubleshoot more this week and will try to follow up the result.