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MG MGB Technical - Wiper Wiring

My '67 GT has a hardware-store, on/off toggle switch in place of the original wiper switch in the dash. The wipers operate at only one speed, and they do not park automatically. Although there is no mention of two-speed wipers for a '67 GT in "The Complete Official MGB 1962-1974", either in the reproduction of the driver's handbook or the wiring diagram, I gathered from the BBS archives that the motor is capable of two speeds. It looks just like the drawing of the "later" motor in the Haynes manual.

Looking under the dash, I found that the motor has four wires coming out of it. One black, one black-and-green, and one green all look like they belong. There is also a green-and-red wire that looks like it was added by a previous owner, and that's the one connected to the switch.

Can anyone confirm that the black-and-green and the green are original? Can you tell which is for low speed and which is for high speed? Thanks. -G.

Glenn G

Hi Glenn.

Have you tried looking at

http://www.mgcars.org.uk/electrical/wipers.html

HTH.. Don
Don

Lot of discussion over this recently. The Workshop Manual schematics imply there was first a single speed, then a 2-speed with a simple parking arrangement, then a 2-speed with a more sophisticaed parking arrangement. Clausager implied that the GT always had the later 2-speed arrangement, the roadster having the single-speed and the earlier 2-speed before getting the later 2-speed. But at least one person has found a fourth variant and that is a single-speed with the later parking arrangement, on a GT, you could well be another.

Square motors have the simple parking arrangement, round motors the later.

The early wiring was black/green for the single or slow speed, and light-green for the fast speed at the switch and motor. The dash switch connected a ground to one or other of these wires. The motor also had a green (fused ignition) wire, i.e. 3 wires at the switch and 4 at the motor.

Later 2-speed wiring is more complicated, with green (fused ignition), red/light-green (slow), blue/light-green (fast), and brown/light-green (park) wires at the switch and motor, plus a black at the motor, i.e. 4 at the switch and 5 at the motor.

The fourth variant has green, black/green and red/light-green at the switch and motor, plus black at the motor, i.e. 3 at the switch and 4 at the motor. This type only has a single speed. I'd have guessed that the black/green is the 'run' wire and red/light-green the 'park', but unless the wires have been swapped round on your motor it is the other way round. If you switch off the wipers so they are not parked, then connect the red/light-green to a green, and the wipers park, you will know the score. An early headlight switch should have the necessary contacts to park as well as run the wipers, it needs a normally closed contact to park as well as a normally open to run. The 'run' wires goes to the common, the green to the normlly open, and the 'park' wire to the normally closed.
Paul Hunt 2

HI Glen

Paul and Iain helped me figure this out on my 67 BGT. Your wires are correct (at least they match what my 67 has). So far, I have not found anyone on this web with a 67 GT that has a two speed wiper. I am unsure why the descrepency in Clausager.

Here is a link to the archive discussion. http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=71&subjectar=71&thread=200509160548598636

Here is a link to some pictures of mine.

http://community.webshots.com/album/452875674DarpYo

I am currently working on seeing if a 2 speed later model will work. Issue is the gear sweep. Have not installed the new unit yet, but the original has a 115 degree wheel and the new one has a 130 degree. So I don;t believe it is going to work. Geer is interchangable, but parking systems are different so it will not park if the gear is swapped.

The older MBG three position light switch can be adapted for the two speed motor.

I also wonder if you could turn the single in to a two speed. Paul or Iain, is the only difference the addition of the 3rd brush or is there a winding/ communuter difference?

Bruce Cunha

I put Paul's info together with the parking info at Don's link and came up with a plan. The description of how to make the early wipers park like the later ones was especially helpful, because it seems that is exactly what someone, possibly the factory, did to my wipers. All I had to do was tag the diagrams with the colors of my wires.

And test, of course. Using Paul's suggestion, I ran the wipers by grounding the red/light-green wire and cut off the current when they were in the middle of a sweep. Then I touched the black/green wire to the red/light-green. The wipers parked neatly.

Now all I have to do is to install a switch that will do the job. Moss wants about $55 for a replacement. I kinda like the old metal toggle switches, and McMaster-Carr sells a DPDT, on-on example for $7, so I ordered one this evening.

One more question, please. The wipers are parking on the left, and I would like them to park on the right. Any idea how to make this happen?

Thanks, guys, I appreciate the help. Bruce, it's good to know that there are others with the same setup. -G.
Glenn G

Glen

I may have an extra switch. I will check on Friday. The switch Moss sells as the GT for the 67 is odd. Don't know why there is a difference between roadster and GT. Roadster switch will work just fine for the 67 GT.
Bruce Cunha

Which side they park is something else I have never understood. Every single LHD example in Clausager shows them parking on the right i.e. the same as RHD, but lots of North Aericans have said theirs park on the left. I believe the change is relatively somple, just a matter of prising the parking cam out of the big gear wheel inside the motor and replacing it 180 degrees out. The arms will probably need relocating on the spindles, so remove them before testing or you may sweep your bonnet/hood.

I *think* the only difference between 2-speed and 3-speed is the provision of a 3rd brush to one side or other of one of the existing brushes.

Glenn - thanks for confirming the colours of the 'run' and 'park' wires.

Bruce - if the roadster had the single-speed with old parking system and the GT the single-speed with the new parking sytem then they potentially they would need different switches. Whilst the earliest switches were 'standard' items with several contacts which could be used for lights and wipers with either park circuitry, these were later changed to have less contacts and were function specific, presumably saving a few groats for BL.
Paul Hunt 2

Paul

That could be it. My wiper switch appears to be the same as the heater switch, although I can't cofirm the heater switch is correct either.

Any 67 roadster owners able to get the numbers off your wipers so we can compare?
Bruce Cunha

I can confirm the one speed GT set-up as my car has this. Its a very early 67 GT built onthe 4th ond 5th of January 1967.

Regarding the park - My wipers stopped parking correctly (at all infact) and that was down to grease from the gears insulating the park switch inside the "wheelhouse"(?).

Haven't checked the wires will do tomorrow.
Niels

This thread was discussed between 10/11/2005 and 20/11/2005

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.