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MG MGB Technical - Wipers all wrong

I have a 1967 Roadster (RHD). Recently the wipers just stopped in the centre of the windscreen. I pulled the motor and rack, cleaned the comm, measured resistances and checked that motor worked. Cleaned out some of the axle grease from the gearbox, cleaned the park switch and reinstalled. Now the wipers park in the middle of the windscreen and start working left to right instead of starting right to left (viewed from sitting in the car). I have repeated the pull several times but haven't found anything worthwhile to do except curse. Could the polarity on the motor be wrong and if so. how should it be changed? Thanks in anticipation.

(Motor is a square one, single speed)

Doug Dell
D G Dell

If I can imagine mechanically how the wiper motor works, rotating around an asymmetric centre to alternately pull and push the cable, then it sounds like the asymmetric timing is off somehow - should be a simple fix by pulling the motor apart and checking everything is lined up as appropriate.

Might now be a good time to go with a dual-speed motor?


Curtis Walker

Is the sweep correct?

If so, you have the park switch in the wrong position.
On the early motors you can rotate the top with the park switch until they stop in the right place.

The park switch is copper segments on top of the large wheel, and spring contacts under the lid that keep the motor running until the contact runs into the break in the segment.
Martin Layton

Doug

Paul Hunt is a regular on this board. He is one of the best on wipers.

Paul Hunt, Solihull, UK, http://www.mgb-stuff.org.uk paul.hunt1@blueyonder.co.uk
BEC Cunha

I found recently that my wipers have decided to stop working altogether. They seem not to have enough power to get the wipers across the screen. There is a bit of play where the motor is attached on the bulk head area. Is the motor supposed to be proper tight against its bracket?

Has anyone made a modern windscreen wiper conversion as when they work they still aren't that great. Id just like a mechanical link bar version like on all other cars!

SGE Granville

If the blades still sweep the correct area of the screen, i.e. don't sweep half the screen and half the bonnet, then the problem is with the park switch. If the blades come off the screen then the relationship between rack and pinion had changed somehow, which can be corrected by removing the arms from the spindles and correctly positioning them, noting which way the spindles turn before refitting the arms! But if this *has* happened then unless you find and correct the original problem it could happen again. One cause of this affecting both wipers is when the rack cable starts to pull out of the 'little end' of the crank attachment inside the gearbox. Where it affects only one blade it is the gearbox for that blade or the rack where it goes through it, loose or worn. New racks are available (but have to be cut to length) and do correct a lot of the slop in old systems. You can also remove the arms from the spindles, mark the top of the spindles, pull the rack out, rotate the spindles 180 degrees, and fit the new rack and that used a previously (unless a PO has already done it) unused portion of the gearbox which removes even more slop.

There are at least three types of motor around 67, with three different wiring arrangements, swapping from one of the single-speeds to one of the two-speeds isn't a trivial excercise, needing additional and changed wiring and a different switch.

I've never heard of a bar system being retrofitted to an MGB, I'd imagine it would take a bit of engineering with all the other stuff that is there taking up the required space for the side-to side movement of the bar at the motor end as well as the back and fore movement all through. The motor does move a bit as it is mounted in rubber pads to reduce noise, and the movement will be greater if the rack, gearboxes, spindles (all of which can stiffen up) and blades are more difficult to move than they should be. Excessive movement of the motor with slow running does indicate the problems (or some of them) are mechanical outside the motor, and not inside the motor or electrical feeding it. Check the condition of the rubber and that the clamp bolts are tight and not just siezed but not clamping the motor properly.
Paul Hunt 2

Thank you for all your advice. It was, of course, the park switch. Somehow when fiddling around earlier, I had got the rotating contact out of sync with the rack position. So I rotated the gear wheel to fully extend the rack and positioned the park switch disc so that the contact was on the insulated part of the disc. The result is not perfect but good enough for a car that seldom goes out in the rain.
D G Dell

I also came across another point to check. If the bracket that holds motore in place is not tight, the motor can slide down a bit. This will change the exact position where the blades end up.

Found that each time I pulled the motor and put it back. If I did not put it in the same place, I had to readjust the wiper arms to get the arms to set at the correct spot on the windshield.

I do have one problem that someone may be able to help with.

Drivers wiper has a small triangular area just to the left of center that it does not clean. If I fiddle with the blade, I can get it to wipe completely, but if it sets and I try the wipers again, the unwiped area comes back. I have new blades and lubed the pivots on where the blade attaches.
BEC Cunha

Of general interest to those who have yet to clean up and restore their wipers, of any vintage MGB, is that wiper motion will also reverse from what it was IF you accidentally or intentionally change the relationship of the rack to the wiper wheel boxes.

That is, if your rack entered the wheelboxes along their bottom edge before removal, and you then reinstall with the rack running across the top of the wheelboxes afterwards, your wiper motion will be reversed also. I purposely did this on my GT simply to park them on the RH rather than the LH side in order to move them out of the driver's field of vision when not in use in a USA car. FWIW.
Bob Muenchausen

That had never occured to me before, Bob, usually we talk about altering the park switch cam on the main gear to change the parking position.

Parking position has always puzzled me. Clausager shows all LHD cars (i.e. *all* cars) with the wipers parked on the right. And while Paul Tegler's colours page shows a number of cars with them parked on the left many LHD cars also have them parked on the right.
Paul Hunt 2

I was looking into this myself as I have fitted a 3 wiper system to my Roadster. Nearly all the photos I could find showed that the wipers were parked on the right, USA / Europe and UK GT's and Roadsters, but all wipers that parked on the left were from Europe, (LHD, mainly Holland) and were GT's!!!
Dave
D M Tetlow

Vairy interesting ... although sadly not borne out by the Parts catalogue which for everything but Mk1 roadsters shows LHD and RHD versions of the main gear without specifying any differences between markets other than that, which it does do for many other parts. The Mk1 also has two gear wheels but the change is on chassis number. Not being so rash as to say your wrong, though.
Paul Hunt 2

For "your" read "you're"!
Paul Hunt 2

This thread was discussed between 04/11/2007 and 14/11/2007

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