View Full Version : TR4/4A TR4 windscreen wipers

08-15-2005, 04:21 PM
Good day everyone,

I am re-installing the wiper assembly on my TR4 and have run into a bit of a snag. The wipers are only moving about 4 inches. What adjustments are there that I don't know about? Also, how does the cable(?) that runs through the wiper wheel box work? Does it twist or push and pull?

............Thanks, Alex

08-15-2005, 04:48 PM
I can't remember off hand what adjustments there are. When you say they only move four inches, do they do that then stop, or do they only go up four inches then return etc.

As to what the wire does, it goes back and forth if I recall. There is a worm and wheel inside the gear head of the motor and the wire is attached to the outside of the wheel and so it goes out and back once per revolution of the wheel. If I remember well there is a contact of sorts also attached to this that sets the "park", this may be what is not right for you. I would have to look it up when I get home if you need to know more.

Geo Hahn
08-15-2005, 07:05 PM
Yes, it's an 'In & Out' (like the California burger joint).

The parking bit maintains current to the motor after the switch is off until it reaches the 'park' position. It can certainly get out of whack (adjusted by loosening and rotating the top of the gearhead) but maladjustment here usually just causes the wipers to park in some odd spot.

You can certainly open up the top of the gearhead and you will see how the cable assembly fits over a pin on the shaft connected to the gear. Note how the cable end clips to the shaft. The Moss catalog has a fair picture. If you remove the cable from the shaft pin you should be able to push & pull it to work the wipers and thus see if it moves freely or binds.

08-16-2005, 10:41 AM
Thanks for the replies. I have a better understanding now, but still fighting with it. The wipers don't seem to cover a lot of the windscreen. When I re-install the motor assembly, where should I have the cable? All the way out? All the way in? Does it matter?


08-16-2005, 11:42 AM
It shouldn't make any difference what position the "whip" is in. It goes straight in and out, and if your wipers aren't moving in the right sequence, or arc, pull them off the splined wheels and reset them. Now, having done that, if they aren't covering the windshield (the total sweep of the arc isn't all that wide), I would think the others here are correct--it may be the position of the deliberate "dead zone" built into the round cover on the motor.

The manual warns that when you remove the cover, it should be replaced with the dead spot in the same location. You'll see it under the cover. It's a black metal area. The cover rotates, meaning you can adjust the point at which the dead spot de-activates the negative current. You shut off your wiper switch, but the motor continues to run until the dead spot is reached where the negative power is "disconnected."

Having said that, I'm not sure misalignment of the dead spot would cause the problem of a short arc, but it may. There is a Lucas Fault Diagnosis booklet that may tell more, and if I find mine I'll follow up. But first pull those wipers off and be sure to put them back on correctly, resting near the bottom of the windshield when the power is off. Good luck.

08-16-2005, 02:27 PM
First assuming that the TR4 and TR6 are similar, and I think they are...

I doubt that the dead switch is the answer to the short sweep of the wipers simply because the dead-position switch is activated at only one position of the drive gear, and has to make a full rotation - thereby driving the cable fully in/out on re-energizing the wiper motor.

My thinking is you have some sort of a mechanical problem.

The spirally wound wiper cable interfaces with a gear in the wheel box. When the cable is pushed/pulled, it oscilates the gear [CW-CCW]. If you are only getting four inches of travel, the cable is either binding, the wheel box bearing are worn enough for the gear is slipping off the cable, or the cable tubes are slipping in/out of one or both wheel boxes.

Since both wipers are doing the same thing, the probability that two wheel boxes have bad gears is high, but not unheard of.

You can check all this without removing anything, by just operating the cable in/out by hand. Pop your wipers up-off the windshield - but you can leave them attached for this test. Disconnect the cable from the wiper motor and with one hand push/pull the cable while the other rotates the wheel box to check for a rough spot or resistance. ( I would use the farthest wheel box from the wiper motor) This should operate rather easily. If difficult then you will need to pull the assembly out for a closer inspection.

When you remove the cable from the drive, you can inspect the worm gear and wiper motor drive mechanism. The electric motors are fairly bullet proof and probably not at fault here. Normally they work correctly or don't work at all.

Hope this helps.

Be sure to note the way the assembly is arranged, especially the wheel boxes, because they can go in backwards and you will end up wiping your hood...Don't ask me how I know this.

08-16-2005, 11:53 PM
Thanks everyone, I've got them sorted out. It was really simpler than I was making it. I ran the wiper motor without the wipers and marked the high and low ends of the sweep. Installed the wiper in the low/parked position, ran the wipers and made some small adjustments to the park position. DONE! Thanks a bunch.


08-17-2005, 03:24 PM
How many "wipes" per minute are now getting?
Mine seem awfully slow (probably shouldn't get caught in the rain)

Geo Hahn
08-17-2005, 03:41 PM
Just guessing from (recent) memory... they run about 1 cycle per second, i.e. 60 wipes per minute.

If yours are much slower I'd check for a binding cable or poor brushes. Brushes can be replaced without pulling the motor if I recall correctly.