Over enthusiastic windscreen wipers.

[Steve_B]

Hi all,

With all this rain around I've had cause to use my wipers a lot more than ever before. Up until now they've always behaved well and clear the screen very effectively.

 

The problem I have is they've started to not stop once switched off. The two stages, fast and slow work fine, but when I push the switch in from either setting they run on.

Sometimes this is for just a few cycles, sometimes for a few minutes.

If I switch the ignition off and then on again they seem to reset themselves (no Microsoft jokes please).

Also if the screen goes a little dry they also stop mid-cycle due to the increased friction. So I'm concerned about burning something out if the motor is trying to run.

 

Before I start stripping everything apart does anyone know if the likely culprit is the switch on the dash or the wiper motor itself?

 

Thanks.

[peejay4A]

It sounds as though they're running on a bit too far when you switch off with a wet screen which takes the mechanism past the self park position so it coninues with another cycle. It does that because when you switch off the motor switch goes into the fast position before off. Also there's no armature short circuit to stall the motor so that it stops promptly. You might get away with adjusting the self park position but if the motor stalls on a dry screen it probably needs attention.

[Steve_B]

Thanks for the quick reply.

 

It only stalls on a dry screen when the rain stops and the wipers are 'running on' , when the switch is in the off position.

If the screen is dry and I switch the wipers on, they work fine and stop as they should.

 

So it sounds like the self park adjustment is the first thing to try. I've not done this before, is it a simple procedure?

[Grahamgl]

Hi Steve,

You should not use the wipers on a dry screen, there is a risk of them stalling and damaging the wiper motor.

The self parking function is controlled by rotating the dome that is on top of the wiper motor, it has a wire attached to it. The dome is held in place by two small screws. It may be that the screws have come loose thus allowing the erratic park function.

Graham

[Mark1965TR4aBRG]

Fast & Slow - mine are Slow & Slower and wiper parking is carried out by a well predicted switch flick!

[boxofbits]

Hi Steve

 

Check the continuity between the red wire on the top of the motor and the contact under the cover. The motor should automatically stop when the brass 'wiper' inside the motor comes into contact with this. Also check black earth from motor to body.

 

Kevin

[peejay4A]

I might have misunderstood but it's the other way round, the motor stops when contact is broken by the self park contact. Steve's motor seems OK from his further info, and the park works but not with a wet screen. So loosening the screws holding the self park cap in place and rotating it, ever so slightly, to find the sweet spot should do the trick.

 

Mark if yours are that bad then they need attention. My wipers are very good on both speeds.

Edited June 17, 2016 by peejay4A

[stuart]

Be very careful with adjusting the park as the bare contact on top of the dome section can very easily contact the underside of the bonnet cone bolt which is right above it!

Stuart.

[Steve_B]

Thanks everyone for your input, sounds like an easier fix than I had imagined. MoT day tomorrow, so I'll have a play beforehand.

 

Regards,

Steve.

[snowric]

Steve, sorry if this is obvious and checked already but I have had enthuiasm like this when the wipers came loose from the wiperboxes. I screwed up the fittings and the problem sorted.

 

I think that what was happening was that as the wiper arms came loose they did not settle in the self park position in the motor and so the motor could keep running so check those wipers are firmly attached too.

Snowy

[peejay4A]

Good point snowy. Too much slop in the wheel boxes could be s problem.

[AlanT]

Maybe you have wire the switch so it goes OFF FAST SLOW. If so then alter the connections so it goes OFF SLOW FAST.

 

There is not a lot of "adjustment" available on the parking contact. Just a bit by bending it about.

 

Here are photos of the inside of a parker:

 

 

[peejay4A]

I don't think you can simply alter the connections in that way.

[AlanT]

You certainly can. And I'll bet this will fix it. Study the way the switch works. It's just a bit less obvious than doing it the other way.

 

 

 

Edited June 17, 2016 by AlanT

[AlanT]

Actually it just came to me that wiring the switch for OFF FAST SLOW is a really bad idea.

 

This means that the motor is having to start with weak field and so a reduced torque. Hence the worry about "dry-screens".

 

It like starting off in second gear and then changing to first. If the factory did it this way they were barking.

[peejay4A]

Yes of course you can if you want to replace the proper switch with the wrong one. The TR4/4A pull switch is the same as the TR4 lighting switch.

 

And a motor in good condition has no problem starting with a weak field - in my experience.

 

I guess you could use a relay to "reverse" the operation of the wiper switch.

Edited June 17, 2016 by peejay4A

[AlanT]

Nope. This is the wiring for the original TR4A switch.

 

The photo shows a "paddle" version but the contacts work exactly the same.

 

I reassembled a pair for Paul Anderson and checked them just like the paddle one.

 

As a matter of fact if you have a broken TR one you can fit the push-pull action onto, an easily available, new Lucas MGB one.

It is a bit tricky.

[peejay4A]

How many terminals are there on the back of a 4A wiper switch? Without looking I can't be sure but I think it's 3 so I must have the wrong switch in my car.

[AlanT]

It's like the diagram. Eight spaces for terminals, only five are fitted. Positions 2,3 and 5 are blank.

[peejay4A]

There you have it. I have the wrong switch. Thanks Al, I'll swap it.

 

Edit: isn't the switch moot here though? When you switch off and the park circuit takes over, they go into fast speed - at least mine do.

Edited June 17, 2016 by peejay4A

[AlanT]

Quite right. They park at FAST speed.

 

When Imade a two-speed, 110 degree sweep, motor for someone, it jumped the parker if running FAST.

But if I switched it to SLOW then OFF it parked OK. They probably don't get to full FAST speed during the first sweep.

 

Maybe the OP has a 110 gear because I've not had a 120 that jumps the parker.

 

Since I often dismantle the caps, I'll make the gap in the brass bigger, if I get this problem again.

 

..

[Mark1965TR4aBRG]

Mark if yours are that bad then they need attention. My wipers are very good on both speeds.

They work just fine peejay - would like a foot switch like the main beam and as the MKI escorts had just for a manual wipe. Otherwise it's a well timed switch flick - all part of the fun.

[peejay4A]

If you can put up with it then who am I to nay say. Personally when it's chucking it down I prefer my wipers to be up to the job.

[AlanT]

When I get an old motor they often struggle to do 30 rpm and running current is above 5A.

 

After I have cleaned and lubricated and done a few other subtle things, they take less than 3A and get up towards 40rpm.

 

Normally it's corrosion between the gear and its bushing thats the problem. Water gets in here.

[keith1948]

Wipers eh - I had a problem where they stopped mid cycle especially when I switched on the indicators. I think I have traced the problem to a loose fuse in the fuse box ignition circuit.

If wipers continue and don't stop then I wonder if the insulation has worn through inside the dome (see Alan's first photo of inside of dome). Also check that little dimple on top of dome is on the right (in line with groove on top of cover to gear housing) for parking wipers on drivers side. (dimple on left for opposite parking).

Switch on mine is off-fast-slow as per TR4A handbook and works fine.

Keith

p.s. Alan thanks for all your help re wiper motors. Hopefully mine is back to working ok now.