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Discussion Starter #1
I have just installed a new wiper motor. It works o.k. on slow speed and parks correctly, but on fast, the speed fluctuates every second or so, yet if I connect it directly to the battery it works fine. I thought it must be a faulty switch but replacing it with a new one has made no difference whatever. Can anyone help please?

Des C
 

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Discussion Starter #3
Thank you for the suggestion which is logical, but the motor is temporarily grounded directly to the battery (as it is not presently bolted in place). Therefore this is the same ground I have been using when running the motor directly from the battery so I don't think it can be that. Also all the connectors are new except for 8 pin multi connector under the center consol. I have cleaned up the terminals on that already but perhaps a further clean up might cure the issue.

Des C
 

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Does it do the same if you put the wiper blades up (away from the screen). Any "clonks" from the mechanism? Is it the same if you press and hold the screen washer button? Worth checking that the fuse is getting a good contact
 

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I have just installed a new wiper motor. It works o.k. on slow speed and parks correctly, but on fast, the speed fluctuates every second or so,
Can you clarify what you have written. Specifically:

- When you say "the speed fluctuates every second or so", does if fluctuate in synch with the motor passing through the "park" position? That is, if the wiper blades take a second or so to complete a pass, is it slowing down when the blades are in the same position each time?

yet if I connect it directly to the battery it works fine.
- It works fine with what connected directly to the battery? You mean by bypassing the switch and just touching the wires to the battery positive?

the motor is temporarily grounded directly to the battery (as it is not presently bolted in place).
Sounds like the motor is running with no load, just "hanging in the breeze". It might work just fine when installed in the car, when the linkage and blades are attached to provide additional inertia.
 

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Discussion Starter #6
Thanks for the posts. So far I have only tested the motor (without connecting up the wiper mechanism) so the lack of inertia might be the answer. However what puzzles me is that it runs smoothly when wired directly to the battery, but when plugged via the wiring loom and switch,it does not. Incidentally the fluctuation is once per motor rotation. I will try with mechanism and wipers fitted.
 

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what puzzles me is that it runs smoothly when wired directly to the battery, but when plugged via the wiring loom and switch,it does not....the fluctuation is once per motor rotation
OK, I'm going to change my mind about installing the motor. What I think is happening is that the motor isn't getting power as it passes through the "park" position when you have it connected to the wiring harness. When the motor isn't driving a load, it can coast through that part of its cycle, but you will hear it slow down as it is briefly running without power. If you connect it to a load (e.g., install it in the car with the mechanism & blades) it may stall as it tries to pass through park.

Is it possible that you are connecting things differently between using the harness to power it and when you wire it directly to the battery? Specifically, might the lead that powers it through park not be hot in the harness? Have you used a voltage tester to confirm that the same wires are getting power through the harness as get power when you wire it directly to the battery?

Still, it's odd is that it runs smoothly on low speed - I assume both with the harness and when wired directly to the battery. If the "always hot" wire wasn't hot in the harness, then the motor would slow down on both low and high speeds while going through the park area.

You said that the park function works OK. Can you get it to park when it's wired directly and running it on high speed?
 

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Discussion Starter #8
Thanks for the advice, so following that, I connected the slow speed and park feeds directly to the battery and the motor runs smoothly at slow speed and parks as it should. However when I connected both the fast feed and the park feed, the speed fluctuates every rotation, although it does still park correctly when I disconnect the fast feed. If I connect the fast speed without the park feed, the motor runs smoothly at fast speed, so it is the combination of the park and fast feed together which causes the problem. Any ideas??
 

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...I connected the slow speed and park feeds directly to the battery and the motor runs smoothly at slow speed and parks as it should. However when I connected both the fast feed and the park feed, the speed fluctuates every rotation, although it does still park correctly when I disconnect the fast feed. If I connect the fast speed without the park feed, the motor runs smoothly at fast speed, so it is the combination of the park and fast feed together which causes the problem.
Are you describing what happened 1) when connecting the motor's wires directly to the battery or 2) when going through the car's wiring harness?

Is it possible that what you think are the park, high and low wires really are not? In other words, that the replacement motor uses different color codes / different spots on the connector than did the old motor? Here's what leads me to suspect that something isn't wired correctly: on my Sprint GT, the red wire to the motor is always hot, only the green wire is hot for high speed and BOTH the green and black/white wires are hot for low speed. Your description sounds like you are only connecting one wire for low speed, though I can't explain how that would produce the symptom you describe.

Did the old motor work OK with this switch and harness before it gave out?

Is your floor switch connected?
 

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Is your wiper switch the 8 pin type?
 

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Discussion Starter #11
Is your wiper switch the 8 pin type?
Yes it is the 8 pin switch. In answer to Alfajay, I was describing what happened when the motor was connected directly to the battery so no loom or switch involved. You are correct that the wire colors coming out of the motor are not the original colors. On my wiring diagram I have white (slow), green (fast) and red (park). On my new motor fast is yellow, slow is green and park is white. I do not have a floor switch, but neither did the previous motor when it was working. The old motor did not fail, but the car has not moved in 30 years and the motor was rusted up!
 

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I am aware that there were 3 wire motors and I thought that they were used with the 5 pin switch. I am familiar with 4 wire motors that use a 12 pin switch. In this case red is fast, green is slow, black is always hot (12V) and brown is park. Brown is fed from the micro switch which is itself fed from black - 12v. Brown is hot at all points except park. when the switch is in park it connect the brown wire to the slow connection of the motor so that it runs until the micro switch disconnects black from brown then the motor parks.

I don't know for sure how the 3 wire motor is wired. I think that you may be trying to run a 3 wire motor from a 4 wire control circuit.
 

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I don't know for sure how the 3 wire motor is wired. I think that you may be trying to run a 3 wire motor from a 4 wire control circuit.
Yes, that is the sort of situation I was thinking of too.

Des C said:
You are correct that the wire colors coming out of the motor are not the original colors. ....On my new motor fast is yellow, slow is green and park is white.
How do you know those are the assignments? Did the new motor come with the wires labeled or with a diagram?

Have you asked the motor supplier about this issue?
 

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Here is another observation. With a correctly operating wiper system if you flip the wiper arms so that the blades do not contact the glass then the park may not work because the momentum of the system is like a flywheel and it goes past the park position where the motor has no power through to the run part of the cycle. Also, on a correctly working system if you switch the fast and slow connections to the motor then the park tries to work on the fast speed and now the increased flywheel effect defeats the interruption to the power to the motor when it is switched to park even with the blades rubbing on the glass, Then you may observe it slowing down at the park position but not stopping.
I don't completely understand how you are doing it but I think you may be observing this effect.
 

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Discussion Starter #15
The new motor was unlabeled and there was no wiring diagram, so I tested each wire in turn directly to the battery to see what each did and identified each function. I have also seen a thread elsewhere on this website explaining the same wire colour differences some new motors which matched my situation. Besides I had the wiring tested so I am reasonably confident the motor is connected correctly. I did ask the supplier about it, but they just sell parts bought in from various suppliers. They have helpfully offered to replace the motor, but of course I don't know if it is faulty..
 

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I tested each wire in turn directly to the battery to see what each did
Go back and read what I posted. The 4 wire motor does not work that way and maybe your's does not either.
 

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Des C:

I'm agreeing with alfaparticle. The word "each" in your post is what disturbs me. Admittedly I am familiar with the 3-wire motors - not the 4's. On the 3's, you need to connect the wires to +12 in pairs to obtain certain functions.
 

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The fact that you have an 8 pin wiper switch tells me that your car originally had a 4 wire motor. To verify that, take a look at the connector for the motor in your car's wiring harness. If it has 4 wires - Blue, blue/white, blue/black and gray then you should find the correct 4 wire motor for your car.

If the floor switch is removed the motor will not run at slow speed unless two of the wires, both blue/white I think, are jumpered together. I suggest that you put the wiper parts and circuits back the way that they were originally. You may be able to creatively make it work with different parts but it will come back to haunt you or the next owner of the car.
 

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If you don't have the floor switch it's the wiper park function that won't work. Jumping the two blue/white wires on the harness will enable wiper park without the switch.
 

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Discussion Starter #20
I have concluded that the problem is not related to either the switch or the loom by testing the motor on a bench with just the battery. My understanding is that the park feed should be live all the time, yet if I connect both the fast and park feeds at the same time the motor speed fluctuates, whereas if I connect the fast feed on its own, the motor runs smoothly as it should. Baffling!
 
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