View Full Version : Wiper Motor Wiring Question

08-03-2012, 07:29 PM
Despite my efforts to rebuild the original wiper motor in mt TR250 it does not have quite enough oomph. It will won't move the wipers on the slow setting, and it is intermittent (needs lots of water to lubricate the windshield before it will work).

A friend gave me a motor from a later TR6 (round case vs. square case). It runs very strong, and appears it will fit with some futzing with the mount.

But the wiring has me a little stumped.

The old motor has three wires, the new motor has more

If you look at the chart from Advance Autowire you will see the change in the switch and the motor.


I want to use the new motor with the old switch.

Black is ground, easy enough, the red and light green and blue and light green make it go on the bench when I touch them to 12 volts.

I assume the Brown/Light green is for the self parking? but where would I route it to on the old car?

Any thoughts from the "electronically blessed" appreciated, and please in simple terms :jester: as in hook this or that to a specific wire or ground.

Thanks in advance for any thoughts or theories. Sorry but my electrical knowledge sort of stops at power to device to ground completes circuit and makes it spin (or light up).

08-03-2012, 07:52 PM
Motor may be OK but your cable that drives the wipers may have old, hard grease that is causing the poor movement. Just a thought.

08-03-2012, 08:10 PM
It is actully a good thought. I could not get the nuts off the wiper spindles when I redid the car, was starting to bend the sheet metal sorrounding them, they were frozen solid, tried PB blaster, etc. No go, the cable was stiff, I PB Blaster, moved it back and forth manually, then WD40, then some spray oil to try to loosen it up. It loosened up, but not the the extent I would have liked, but it is as good as it is going to get, so I am looking at other options, like a hopefully stonger motor.

08-03-2012, 08:51 PM
That ain't grease in there.
Might be an old dinosaur!

08-03-2012, 10:50 PM
You guys are more fun than a barrel of monkeys :banana:

Now lets try to stay on task :nonod:

Wiring :thankyousign:

08-04-2012, 07:15 AM
I think you best clean the tubes out and regrease, you can add a stronger motor but if you have resistance in the tubes you will increase the amp load on the motor and wires ,,,,and most likely burn wires up or blow fuses

I would clean the tubes out and grease them good, the motor is not the problem


08-04-2012, 07:26 AM
You may or may not be right, but as I said I couldn't get the mechanism off with the car all apart, I am not going to be able to or even try now, I have spent quite enough time under the dash in the last couple years chasing down some minor wiring gremlins to last a lifetime.

08-04-2012, 08:43 AM
To answer your original question, I don't think you can use the TR6 motor, at least without some major modifications. It's hard to tell from the wiring diagrams, as they don't show enough, but here's what I think is happening:

The TR250 motor appears to be two-speed, where the speed is selected by grounding one of two terminals through the switch.

The TR6 motor seems to be three-speed, and speed is selected by powering one of three terminals, not grounding it.

The final wire is just the positive voltage to the motor.

So, they seem to be fundamentally different. The only way it would work, I think, is to disconnect the ground from your switch and run the +12V to that switch terminal--then you could power two of the three speeds. But this sounds like more than you want to get into, and it all depends on whether my assumptions about what's in those boxes marked "switch" are correct.

But I also agree that it's likely the problem is in the cable.

08-04-2012, 10:47 AM
Any difference in the look of the 2 switches.
Can the 6 switch be put in the 4's spot?

08-04-2012, 11:50 AM
Well, how important is the self-parking feature to you? Would you be willing to add a relay and some diodes to the circuit?

Both motors are two-speed motors, but the speeds are implemented differently. The TR250 motor used a wound field and achieved the two speeds by switching the field windings. That allowed a very simple "ground this wire" park switch, and no support from the control on the dash.

The TR6 motor went to a (less expensive) permanent magnet motor, which of course means the field is fixed. It achieves the second speed by using a third brush, which effectively bypasses a couple of windings on the armature. But since it can't have both brushes connected at the same time, the park circuit got more complicated and basically the dash switch has to make a connection in the 'Off' position that the TR250 switch doesn't have.

So, to use the TR6 motor with the TR250 switch, you'll have to either give up on the self-parking feature, or add a relay to complete the circuit through the park switch when the dash switch is 'Off'.

08-04-2012, 12:04 PM
Thanks, kind of what I was afraid of, I could live without the self park, I had an early Healey 100, but the goal is to get it all working right so I don't really want to trade one issue for another.

Don't really want to add too many extra items or the later switch, so it looks like (eating crow) I may try to shoot somemore lube into the tube and work it back and forth some more and see if it helps, I did a lot if that when the car was completely stripped and the motor was off, but maybe third or fourth or fifth time is a charm.

If I understand you right, and what I was beginning to suspect as to how it works, there is a third circuit that runs it to "Park" when you have the switch on off and that circuit runs through the switch and the motor, so not easy to adapt with my old switch.

08-04-2012, 12:17 PM
If I understand you right, and what I was beginning to suspect as to how it works, there is a third circuit that runs it to "Park" when you have the switch on off and that circuit runs through the switch and the motor, so not easy to adapt with my old switch.

Exactly. Here's an article by Dan Masters, explaining how the TR6 motor works (although he inexplicably did not include the 2-speed TR250 wiper motor):

Good luck with the "lube in tube" approach, you're gonna need it!

PS, here is a diagram (also by Dan Masters I believe but I forgot to record where I found it), showing the TR250 wiring: