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How do I bench-test a wiper motor?


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Hello all,

 

My TR3 (ROR 999) seems to be failing bit by bit.

Help please, electrics are not my strong point.

 

My wiper-motor became unreliable and started working only intermittently, and now doesn't work at all.

I checked the switch and that's fine and all the connections seem to be OK.

I've just changed the brushes, although they didn't seem to be too worn.

I replaced it in the car but still no joy.

 

Before I removed it, I used a continuity meter across the switch and there was full continuity with the switch both off and on.

In fact, there seemed to be continuity between all connections on the motor.

Does that mean there is a dead short somewhere in the motor?

 

Can anyone tell me how to bench test the motor please?

It's the single-speed self-parking model that was fitted to TR3s after TS12568.

 

Thanks in advance.

 

Brian.

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Hi Brian,

when they start to go it isn't worth the time and effort to chase the problem around. If you are sure that the wiring in the car is ok then get an exchange motor. they are costly (£120) but will out last the car.

I'm sure others would try to repair but at what cost.

 

Roger

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Hello all,

 

My TR3 (ROR 999) seems to be failing bit by bit.

Help please, electrics are not my strong point.

 

My wiper-motor became unreliable and started working only intermittently, and now doesn't work at all.

I checked the switch and that's fine and all the connections seem to be OK.

I've just changed the brushes, although they didn't seem to be too worn.

I replaced it in the car but still no joy.

 

Before I removed it, I used a continuity meter across the switch and there was full continuity with the switch both off and on.

In fact, there seemed to be continuity between all connections on the motor.

Does that mean there is a dead short somewhere in the motor?

 

Can anyone tell me how to bench test the motor please?

It's the single-speed self-parking model that was fitted to TR3s after TS12568.

 

Thanks in advance.

 

Brian.

 

Hi Brian,

 

The wiper motor you have is more than likley a Lucas DR3A as fitted to loads of cars at the time such as minis, heralds spitfires etc so there is a plentiful supply of cheapish spares. As far as I can tell the only difference between them is the large gear wheel in the gear box which sets the sweep angle . I have just rebuilt one for my tr4 using an old mini motor and swapping the gear wheel and flexible drive from the old wiper.

 

If it is a DR3A single speed motor you will find 3 terminal connections on the back marked 1 2 and E the earth.

 

Terminal 2 has a perminent 12 V Terminal 1 an earth which is opened and closed via the wiper switch. ie wiper switch in the off position no crcuit wiper does not operate, switch in the on position, circuit complete motor turns. The E always goes to the earth and is never switched and is used for the auto park feature. If you connect 12 V to terminal 2 and then link Terminal 1 to Earth the motor should turn , if not you have a problem.

 

On the car check you have 12 V on terminal 2, Check when switched on you have earth continuity on Terminal 1 and of course check that the wiper motor earth connection is good ( the terminal marked E).

 

A huge number of electrical faults are due to bad earths causing intermittant problems that become perminent. First check is always to check and clean the earths and the electrical spade connectors or lucar bullet connectors.

 

Hope it helps

 

Alan

Edited by Kiwifrog
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Thanks to Roger and Alan,

 

It looks like it's the motor (type DR2) that's at fault. Using a spare 12V battery, I linked terminal 2 & 1 and then connected terminal 2 to a battery while earthing it, and got not a twitch out of it.

 

So it looks like Moss will benefit again, and of course, it would be the most expensive wiper motor they sell, at £214.96 exchange.

 

Regards,

 

Brian.

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Hello Brian,

 

"I linked terminal 2 & 1"

 

Surely that is wrong, one of those is the feed (permanently live) and the other the switched earth terminal. To test, I would have thought that the switch terminal should go to the earth side of the battery (whichever polarity your car is?).

 

Alec

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Hello Brian,

 

"I linked terminal 2 & 1"

 

Surely that is wrong, one of those is the feed (permanently live) and the other the switched earth terminal. To test, I would have thought that the switch terminal should go to the earth side of the battery (whichever polarity your car is?).

 

Alec

 

Hi Alec,

 

I think you could be right, which is a shame because I have probably blown something when there might not have been anything wrong before!

 

Perhaps I should have earthed one of the connections and the wiper body and supplied live feed to the other connection. When I connected them the other way round, I got a momentary spark from the battery live terminal and then nothing, so I have probably damaged it somehow. A lesson to all to fit an in-line fuse when experimenting with ideas when you don't know what you're doing.

 

Many thanks to those who have supplied contacts. I got through to Stafford Vehicle Components and a very helpful man gave me the number of Steve Hunt who rebuilds motors. Tel: 0121 777 0071 or 07885 186111. I'll be calling Steve later.

 

Regards,

Brian.

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Hello Brian,

 

"I linked terminal 2 & 1"

 

Surely that is wrong, one of those is the feed (permanently live) and the other the switched earth terminal. To test, I would have thought that the switch terminal should go to the earth side of the battery (whichever polarity your car is?).

 

Alec

 

Alec

 

My cock up have edited my origonal post to correct problem, its always confusing working on posative earth cars

 

Alan

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Alec

 

My cock up have edited my origonal post to correct problem, its always confusing working on posative earth cars

 

Alan

 

Happy ending (for a change) :lol: - the motor still works and I'm very grateful to all those who made suggestions, particularly Alec who put me straight on bench-testing and those who gave details of suppliers who might help.

 

Regards,

Brian.

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  • 7 years later...

See my post on 2 speed wiper issues today. I found this link to an explanation of how 2 speed motors work and solved my problem.

 

http://www.britishcarforum.com/bcf/content.php?156-Lucas-DR3A-Two-Speed-Wiper-motors

 

To get fast speed on a 2 speed motor connect green wire to battery + and brown/green to earth and you get fast speed.

To get normal speed connect green wire to battery + as before but connect both red/green AND brown/green to earth) not just red/green as you would have thought. The link explains all. Also continuity testing tells you very little. You need an Ohmmeter because everything is connected either through field coils or armature.

 

Inside my 2 speed motor I cleaned out all the old grease, lubricated the bushes with a drop of oil, and made sure the end float was correct (adjusting screw on back of gearbox. Remove cover first marking circular bit with wire soldered on top so self park works. Measure end float at end of worm drive next to adjusting screw. The bushes at both ends of the commutator drive need to be able to move freely so that shaft locates freely. The bushes swivel in their housing and need a drop of oil. Any mis alignment of the shaft can slow or even stop the motor as I found today.

The article in the last TR Action is really helpful.

Keith

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Hi Pete

yes I know DR2 is single speed which is why I kept referring to my 2 speed motor in my post. Apart from wiring, other points such as cleaning out old grease, setting end float, testing with Ohmmeter and making sure floating bearings move etc however apply to single speed motors as well. The link has a lot of useful info in that would apply to both single and 2 speed motors.

 

Anyhow Brian and I can now go out in the rain again in the TR so happy ending for both

Keith

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This is an old topic but since it's been bumped anyway, here I am bench testing a two-speed motor.

https://flic.kr/p/FKABGX

 

If you buy a DR3A on eBay, for about fifty quid, you have about a 30% chance that it will run properly and be free from major defect.

 

Here is a selection from the black-museum without any explantory comments:

 

26684103286_90f1ff55d2_b.jpg

 

26432217665_a0a2caeda7_b.jpg

 

24632452109_a0fb7014df_b.jpg

 

26828274115_c3dbbb76c1_z.jpg

Edited by AlanT
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Hello all,

 

My TR3 (ROR 999) seems to be failing bit by bit.

Help please, electrics are not my strong point.

 

My wiper-motor became unreliable and started working only intermittently, and now doesn't work at all.

I checked the switch and that's fine and all the connections seem to be OK.

I've just changed the brushes, although they didn't seem to be too worn.

I replaced it in the car but still no joy.

 

Before I removed it, I used a continuity meter across the switch and there was full continuity with the switch both off and on.

In fact, there seemed to be continuity between all connections on the motor.

Does that mean there is a dead short somewhere in the motor?

 

Can anyone tell me how to bench test the motor please?

It's the single-speed self-parking model that was fitted to TR3s after TS12568.

 

Thanks in advance.

 

Brian

 

.My wiper motor has just been overhauled by Alan T and has come back like new. He is a complete specialist and will help you avoid failure. He is a regular forum contributor and has written a long article in TRaction with photographs of all the vulnerable parts.

 

I am very pleased with my motor and would give Alan 10/10.

 

Richard& H.

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A few shots of Richards motor. This was actually in pretty good shape compared to some I've done.

 

26159374130_687d549bd2_b.jpg

 

26339881742_90568e7611_b.jpg

 

26301846450_45eafc8589_b.jpg

 

26508667581_f8bf1e6ffd_b.jpg

 

Deliberately left some sign of age on the cover and cap.

Often I do them more "blingy" than this. Mainly because this is a more weather-proof finish than paint or zinc.

 

20221541434_a2e8779761_b.jpg

Edited by AlanT
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