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MG Midget and Sprite Technical - Wiper/Washer Switch Excitement

Five minutes into a ride yesterday the windshield wiper/washer switch handle started smoking. High drama! The plastic handle just melted and I knocked it to the floor. Pulled over right away. The stalk the handle mounts on was searingly hot.

I’m baffled, but only just starting the process. Luckily Moss stocks the switch assembly that’s right for my 1971, so a new one is on the way.

If my problem is only the switch, I should be fine. I’ll track the wires from the connector that goes to the switch to be sure the ones that don’t go to ground aren’t grounded, and the ones connected to terminals have continuity.

These are my questions: Why the heck wouldn’t that dedicated line fuse have blown? (#67 in my wiring diagram.) I haven't yet found the in-line fuse, but I need to spend more time under the dashboard. Has anyone else dealt with such drama from the wiper switch?

I only use the wipers and the washer once per year, for the safety inspection required in Massachusetts. I do have a modern washer pump from Moss installed two years ago when the inspection process started to include the washer function. The wipers don’t move swiftly, but they move when they should, and they definitely weren’t on at any point during the ride.

Do wiper switches just sometimes decide to spontaneously combust?

Thanks for any ideas.



Mark 1275

Mark, not for it melting usually but I think you made a mistake by only using and testing it once a year, same with other items not used a lot or at all, horns, hazards, side and headlights (for those cars frighten of the dark) and headlight flasher.

Using or testing them and helps stop build up of crud/dust/muck/grit/ect. and helps to keep the contacts clean and prevent and build up that may cause shorting.

I'm not sure what the wiring and fusing is on a NA car (and what's an electric washer!) so may well, as often happens be talking out of, er, let's say the top of my head. Perhaps the heat was so localised and at the contacts spread across more than one set of wires so sharing the heat.

Those with an understanding of electric will give an explanation.

I do know fuses don't really blow but melt and can take a long time to fully melt so the wiring to them can be warming for quite a while. A direct real short, like wires touching or water can/will cause the fuse to melt almost instantaneously and "blow".

There, clear as mud, now for the Middle East situation. 😃

Nigel Atkins

Thank you for responding, Nigel. Still haven't found the in-line fuse, but I did finally get the steering wheel off this evening. Tried all the methods, hammer, bigger hammer (cautiously), penetrating spray for days, heat gun, but it was a steering wheel puller loaned by the local auto parts store that did it.

That plastic cowl is diabolical. Just removed the bolts holding the steering column from under the dash and didn't gain as much movement as I was hoping for. Loosened the bolts where the column goes through the firewall, but then stopped for the night. Hope to go the next step tomorrow. I've gotten to three of the four cowl screws.

I've really enjoyed this little car for the 20 years I've owned it, but I hope this is one of the last times I need to work a lot under the dash. I just don't fit there and no longer have the flexibility.



Mark 1275

Mark, does that wiper stalk also operate the horn on your '71 car? It does on my UK spec one. The wire from the horn is permanently live, and not fused, so if it had found a way to earth via the switch stalk, that may have been the problem.

On second thoughts, that would have made the horn bellow at the same time! Unless of course the horn itself wasnt working. May be worth checking?
GuyW

Mark

Clearly, something is shorting to earth, either partially or fully. I would check the wiper
and washer motors directly first by disconnecting them and supplying them directly from battery via a fuse. If they've seized partially or completely, due to under-use, they'll draw excess current and heat up the switch.

If not that, there must be a short around the stalk or somewhere in the associated wiring, probably washers as the wiper switch only earths.
Bill Bretherton

Mark,
I had a very good 'plastic; steering wheel bent on my r/b B by a mg specialist using a puller, the replacement steering wheel they provided was alright but not as good as my original.

The inline fuse is easy to see and get at in UK cars in the engine bay but sorry I've a feeling, but don't know for sure, with the NA cars it's tucked up behind the dash. possibly passenger side, or is that wishful thinking.

I know what you mean about working around the driver's seat area of the dash, especially with my 15.5" steering wheel still fitted. And the cowl, four screws that are a surprisingly fiddle to fit and often drop to the floor as you can't see to line them all up properly and then you don't want to overtighten so a few says later you feel one under your foot whilst driving.

During the two hottest days of the year I've been working on my car servicing it and getting it ready for the twice postponed weekend touring event. Every planned job finds at least one other unplanned. All those that find 'joy' and pleasure farting about with these cars I'm sure would keep quiet about it if they were around me whilst I suffer my 'adventures'. I literally ache from bending over the engine bay and rolling around on the concrete ground and I still have planned jobs to complete or start.
Nigel Atkins

Thank you for the responses. My car has a horn button in the center of the steering wheel, so one less circuit for the wiper/washer switch. I agree it seems something went to ground, and I'll do all the checks I can think of with a multimeter. I'm hoping the fault is somewhere in the switch assembly, or at least on the switch side of the connector under the dash.

The new switch arrived today and I haven't even opened the box yet. I hope it's the same as the unit I'm replacing, but it almost seems like the price is too low to be a perfect match.

Didn't make much progress last night. Got sidetracked by the desire to prep and repaint the steering wheel metal hub. Probably because it's on the bench and doesn't involve the contortions of working under and around the dash.

It will be a victory to get that plastic cowl off, and I'll continue the campaign tomorrow.
Mark 1275

Well, the switch appears to be perfect. Better than I expected.

So now there's nothing holding me back.

Except Satan's cowl...





Mark 1275

Guy asked if the wiper stalk also operated the horn. That confuses me as I have never come across that. The horn did move to the end of the indicator (turn signal) stalk for a while (I have that on my Triumph Dolomite), but I've never seen it on the wiper stalk.
Mike Howlett

Quite right Mike. On mine the horn push is in the indicator stalk as on an early mini. The wipers on mine are switched from a toggle on the dash.

The question was directed at Mark as his is a N American spec car and I wondered if they put the horn push on the wiper stalk.
GuyW

Horn button is on the stalk switch on my 78.
IDK when it changed.
Greybeard

Successful exorcism!

Had to pull the steering column out a bit, and even then it wasn't a walk in the park, but now I'm on my way.

Electrical checks, make sure I won't fry the new switch, and then lots of puzzling reassembly.





Mark 1275

Ooh, how complicated! The Bugeye has just one wire in place of that lot! All that just to avoid having to move one's hand the extra few inches to a switch on the dash! Progress, I suppose.

But well done for sorting it out Mark.
GuyW

Ha ha. Not even a single wire on my Bugeye. The horn push is a long sprung toggle on the dash, just under the left hand middle fingertip.

Good luck, Mark.
Nick and Cherry Scoop

Well, I'm not finding what I expected to, and sure could use some advice.

Because the only evidence of heat I saw was the melting stalk, I figured I'd find some reason the washer switch was the culprit. On my North American car you push in on the switch end to run the washer. It's a momentary contact switch, you hold it in to run the washer, and because it reached 1000°F and melted it seemed to be the likely source of the problem. Thought I'd be all set: new switch would cure the problem of the old switch, and the problem was isolated to the switch so it shouldn't recur.

But instead, when doing the checks on the wiring I found evidence of heat at the connector that goes on the wiper motor. What the heck. The wiper switch components aren't even near the washer switch, so it seems to me the problem should be one or the other. Now I'm suspicious of the wiper motor and will probably replace it just to be on the safe side.

Not sure how a problem at the wiper motor could melt the washer switch, but I'm starting to understand the set-up is different here and the washer isn't the same over there. I'll take apart the old switch and maybe I'll see something that helps me understand the source of the problem so I don't end up frying my very attractive new switch.

I still don't understand why a fuse didn't blow somewhere. I did find the in-line fuse in the engine compartment. It was just above the fuse box and below the control box (voltage regulator?). It's a Lucas fuse labeled 35 amp, and it also says 17 amp continuous.






Mark 1275

Mark

In my view, 17A or so could melt plastic especially if the switch is corroded and has resistance. The fuse is protecting the cable, not the switch. So you could have, say, a 15A to 20A current flowing, due to a fault, that doesn't blow the fuse but causes heat in the switch especially if it has some resistance. Do the washers and wipers work normally?
Bill Bretherton

Bill, it's been all of a year since I last used the wipers or the washer. It was the last inspection, what I think you call MOT. I just don't drive in the rain, and don't need to use the washer. They did work normally last July, but I'll say the wipers have always moved slowly. I assumed it was because of disuse, and hardened grease in the cable housing.

I haven't tried them since the conflagration, but it's now likely I'll go around the switch just to test their operation before I install the new switch assembly.

I assumed I could get a new wiper motor from Moss, but they're on back order. I hope that's not for long.
Mark 1275

Mark,

It might be worthwhile stripping your current motor and checking the state of the brushes and lubricating the bushes and greasing the worm and gear and sliding parts, that may perk up your motor.
David Billington

David, I agree, but because of that panicked feeling when the switch started smoking, I've already found a new motor from another source, and it should arrive by next weekend.

To verify the motor I was ordering was correct, I tried to pull the old motor to get a good look at it. The bolts and the retaining nut came out easily, but I can't convince the cable to come out. I haven't checked the archives yet, but I've sprayed it with penetrating spray. Are there any tricks to this?

Thank you for the responses.



Mark 1275

I know earlier I was confusing this with the stalk mounted horn push on some UK cars. But the point was that the horns are permanantly live and the switch (push on the stalk end) earths them. If your washer is similarly permanantly live then it could be that the insulation on the wire inside the stalk had worn through, causing a short to the metal tube of the stalk and localised heating there, resulting in your knob melting and dropping off. Maybe that was where the fault was and the washer pump and wiper motors are not to blame and are still in good order?

And, the easiest way of disconnecting the wiper rack cable is to remove the large gear wheel and crank arm from the body of the motor drive. I think it is held in the middle with a circlip after which it just lifts up and releases from the cable end.
GuyW

I know little about American spec cars but problems with burning connectors at wiper motors is probably universal to all models.

I think you probably have the round model type wiper motor and the wiring connects to the auto off switch - clear plastic bit and I've seen a couple of these with burn/heat marks.
I think what happens is the wiper rack gets stiff over time - especially the tube/rack/wheelboxes and the motor driving gears - the old grease turns hard and slows the system down, increases the motor load and over heats the connections.

A good strip out and regrease of rack system and motor often solves this but I've had to replace a couple of the motor park switches on some I've repaired as they had burn marks on the plastic.

It could be that you have found a seperate fault with the wiper motor unrelated to the first issue !

R.
richard b

Mark

In my view, 17A or so could melt plastic. The fuse is protecting the cable, not the switch. So you could have, say, a 15A to 20A current flowing, due to a fault, that doesn't blow the fuse but causes heat in the switch. Do the washers and wipers work normally?
Bill Bretherton

Bill, I thought I responded earlier, but I must not have submitted the post. The last time I used the wipers and washer was a year ago for the inspection (I think what you call MOT). They worked fine then, but the wipers were slow. I'll probably check their operation by working around using the new switch, very carefully with a fused line. Once the new wiper motor arrives, everything will be new except for the harness. I'm even replacing the partially melted wiper motor connector with a connector from an old harness I bought years ago. Different color connector, but it looks like it should work fine.

Guy, I'm glad you suggested removing that circlip. There was no way the cable was coming out without removing the crank arm! There's a heavy duty pin that goes through the cable end. Now it's apart.

Richard, if the new motor doesn't move the wipers at the right pace, I'll try to improve the situation in the tube for the wiper cable. Is there an easy way? Can I just send in new oil, or does it need some disassembly first? I've got so much apart now I'll be surprised if it all goes back together.






Mark 1275

As you have done the hard bit by removing the motor, the rack regrease should be a breeze !(famous last words).

As I remember it just take off the wiper arms/blades and the rack cable just pulls out of the guide tubes.

Clean off all old grease, regrease rack wire and re-insert you will feel as it re-engages with each wiper box, then refit the motor and test including off position.
When auto parked, refit the wiper arms/blades.

R.
richard b

Another thing with post-'68 US cars is that they had three wipers, adding more load to the motor.
Dave O'Neill 2

This spring fell out of the plastic cowl assembly when I took it apart. It's not the same size as the springs that are in the wiper/washer switch. Everything seems to work fine with the directional switch.

Any ideas where this belongs?

Thank you.


Mark 1275

So many additional parts on a NAS car I'd never know, sorry, perhaps DaveO might.

Only spring I can find is 7H 6902 (7H6902?) which is something to do with the horn mechanism for centre push buttons but I can't find an image of it for you so if it is it you don't want to lose it.
Nigel Atkins

Well, that was unexpected. When I unwrapped a bit of the wiring harness to solder in the replacement for the melted wiper motor connector, I found that someone had done the exact same thing before. And I've had the car 20 years.

So I guess sometimes things do spontaneously combust.

The connector from my old harness is now connected.

I'm curious about putting the steering column back on to the splined connector at the steering box. Is there anything that needs to line up? I can't get a good look at the end of the steering column, but I don't see any flat spots or anything I need to take into consideration.






Mark 1275

Finally at the reassembly stage, and I wish I'd taken more pictures before taking things apart.

I'm putting the steering column back onto the spline at the steering assembly. I'm not sure if I'm all the way in, and I don't remember what it looked like before coming apart. I'll see if I'm lucky enough to have a "before" picture.

Any chance someone could check their joint between the steering column and the spline to see if splines are exposed like in the picture?

I'm tapping with a rubber mallet, and once it started to go together it went very easily but only this far. Now it just bounces when tapped.

Thank you.



Mark 1275

I should have checked my files first! I did find a photo from the time I was prepping the engine compartment for painting.

Looks like I'm not quite all the way there, but now I have a better idea of what I'm shooting for.


Mark 1275

Mark, the splined rack part will have a notch in it that the bolt through the clamp locates in. If the column isn't far enough on then the bolt won't align with the notch and go through.
The bolt itself should be a shouldered bolt (unthreaded shank near the head). Your before photo looks like an ordinary threaded bolt which may not locate securely in the notch.

Edit: Difficult to be sure, but zooming on on that photo, the bolt looks undersized and I think the notch is visible just further down the splined piece so it isn't located properly. This is a safety critical item so you need to find out what is preventing the column from going fully onto the splined pinion and being properly secured with the correct bolt.

Less important, but there should also be a collar (nylon?) on the splined pinion to keep dirt out.
GuyW

Mark,
I'm not one for concours appearance but if you take it apart and clean off the debris the clamp might go lower as there appears to be a build up of debris below the clamp which might be holding off the clamp from fully sitting and debris between the splines resisting the sliding action.

I've included a photo of the correct bolt which is a certain shape and length.






Nigel Atkins

Check also that there isn't something up inside the end of the steering column clamp and perhaps slacken the column support bracket at the top of the firewall up under the dashboard?
GuyW

Others will know better than me, but is it best to use copper grease (or other anti-seize compound) on the splines so you can get it apart easily next time?

Jon
Jonathan Severn

Great ideas, much appreciate it.

I'll get the right bolt, the one I have has much more threads. I do have the flat part of the splines up, but I'm not sure if I'm lined up perfectly, or off a spline or two. So we'll try again.

I did take pictures of the inside of the column end and it looked pretty good, but I'll clean up everything. I'm disconnected at the firewall and up under the dash, so I should have free movement toward the splines.

Another area where I wish I'd paid more attention was the distribution of the big washers under the dash. Don't think I'll find a "before" picture of that area.

I do have anti-seize and could use that after cleaning things up.
Mark 1275

It may help to open up the clamp a little with a flat bladed screwdriver pushed into the gap. Once the column is far enough down for the shouldered bolt to locate in the notch remove the screwdriver and the bolt will close the slot back up tight again.
GuyW

That's what I did - just by coincidence. Cleaned it all up, reassembled, and the bolt closed the clamp right back up.

There are three big flat washers that go under the dash, and I'm pretty sure where two of them go. It will be a bit of a guess on the third, but I should know if something's not right.

Making progress a little bit at a time. Hope to be able to bring it in for inspection (MOT) Saturday morning.
Mark 1275

All back together, and I passed the inspection! Much appreciate the help.
Mark 1275

Good news. Now all you have to do is drive it a lot more.
Martin

This thread was discussed between 17/07/2021 and 07/08/2021

MG Midget and Sprite Technical index

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