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Wiper problem


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Hi All, I have just fitted a reconditioned DR3a single speed wiper motor and new 120 gear to my TR4 , the previous ones park control copper arm having broken. Reconnected from the engine bay without touching the wiper boxes. All looked good when fitted and without the wiper arms attached the splines work perfectly, the park function now working as well. My problem is ,with the wiper arms and of course blades fitted I get about one stroke before they "stick " to the window , switch off and on and I get another partial stroke. ,! Friction on window to great? Loosen springs in wiper arms? If it's a wiper box issue I may scream having just replaced the dash and windscreen following other interior work. Your thoughts greatfully received before I bite the bullet and take the dash apart to gain access.

I had searched the forum and other members issues appeared to be total failure of the motor or gear rather than my sticking, but I'm clearly clutching at straws because I don't want to spend another day upside down in the footwell. Kind regards ..John.

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Did this work OK with the old motor?

 

You could have got a new parking-contact from me quite cheaply.

 

I would guess yout replacement motor is running tight and the blades just add enough load to stall it.

There are many reasons they do this. Its's common to have a partially seized gear-shaft.

 

Did you just win this on ebay, perhaps?

Send me a PM.

Edited by AlanT
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Pete, didn't work well before hence I changed the motor , upon inspection old motor looked quite gummed up and park control contact and spline it attaches to were broken so given I had put the dash back I changed this out hoping it was the issue . I've changed the wiper arms in the interim so I'm not comparing like for like , but no it wasn't good before!

 

Alan , as above , I bought it from someone who came highly recommended to me , wasn't won on an auction , I avoided the recent one on e bay as it hadn't been reconditioned, but he does have an e bay

Store. will drop u a pm.txs

 

Graham, that's what I'm hoping , that it works in use, however that leads to

 

In an mot presumably they are tested dry?

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When I take my car for an MoT I hang a small sign on the wiper knob " Please ensure the screen is wet BEFORE using wipers". This seems to work.

Graham

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Yes silly comment by myself clearly I could ensure that it was wet! So used to modern components working

In all conditions , wasn't perhaps factoring in the 50 year advance in engineering.Off to test it now in "real " world

Wiper conditions. Please forgive my stupidity.

 

John.

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FWIW The force required to remove the rack cable from the tubing should not exceed 6lbs force (use a spring balance to check) any more and you risk the motor stalling. Best check that first.

Stuart.

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You really do need to be careful with the alignment of the rack-tubes.

 

If you move the rack-tube that joins to the motor, by rotating it when you fit a new motor, then drag increases quickly because you loose the smooth run in to the wheel-box.

 

Also watch the fit of the "big-nut" on the nipple in the motor. If you cross-thread this, the tube will be out of line.

This will be enough to increase the drag and spoil the performance.

 

As Stuart says the wire needs to run pretty smoothly. This is especially true on the FAST speed. This does not provide as much torque.

It's a bit like the over-drive that trades speed for torque.

 

Its a good tip for the MOT man. Actually back in the 60's we all knew not to run wipers on a dry screen.

Just like we didn't start a car with the headlights on. All these basics are gradually being forgotten.

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Thanks All,

removed motor checked resistance of rack cable , had been careful with rack tube as I was guessing any movement or kink age would lead to a bigger job. Agreed re "big outer nut" very hard given the angle to get this on correctly but did indeed get it on square. Ran the motor for 10 minutes without wiper arms , suggestion from previous posts had been that this could free up moving parts in wiper boxes and cable without as much resistance , not sure about this but didn't think it would do any harm. Re ran with arms fitted and water on screen , hey presto , worked ok. I'm amazed that the additional resistance caused the stalling after just one dry sweep or that just a little water decreases the friction that much, but they now work so I will happily move on to the next job.

Thanks for the input chaps most kind.

John.....

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I run a rebuilt motor for 3 hours at 16V. They get pretty hot when you do this. The current taken will fall from about 3A to under 2A during this period. After they cool the current remains low.

 

This is because the self-aligning bearings take a while to bed in, the carbon-brushes need to wear in, lubricant needs to find a hole to sit in.

 

If they don't behave like this I take 'em to bits and have another go.

 

Time the number of sweeps you get in a minute. The motor makes 45rpm off-load and much under 40rpm on load means something is too tight.

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