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MG MGB Technical - 67 GT Wiper wiring

Hi all

Working on my wipers for my 67 B GT. Motor is a 12W, which Clasanger says should be a two speed correct for the GT.

Wires coming off the pigtail are Black, Green, Black/Green and Red/Lt. Green.

Black is ground, green is from fuse box. Black/green and red/lt green go back to a three position switch. Thre is also a black groud wire for the switch

I can't find any wiring drawings that show this color combo or how to hook them up to the three position switch.

I can get the wiper to go slow and to park. What activates the second speed?

I have read over Rick Astley's web site

and still can;t quite figure it out.

Any help would be appreciated

e-mail is if you have some pictures.
Bruce Cunha

Site mentioned is evidently wrong, there are clear errors so I would not trust it. I can't find that set of wire colors either. Sounds like you have an early version of two speed (which answers some questions in the other thread on wipers!), but the diagram I have has different and confusing colors.
With following info I can mebbe figger it out.
How many terminals on the wiper motor -3, 4, 5? How are they arranged and marked? Are the pigtail wires in a plug or separate push-ons? How many terminals on switch - 4 or 6? Numbers on switch and motor? - will be 5 or 6 digit numbers. Was car originally pos or neg ground? What is the car number?
I can tell you that if the switch is wrong, you can't make it work. Converted a Spridget from 1 to 2 speed once and went nuts. Finally figured out a way to use a different switch with a jumper, don't recall details, but if I did it once...
FR Millmore

Bruce and Fletcher - Another site that contains information on the wiring for wipers that may shed som light on the proper wiring, is Paul Hunt's Pages of 'Bee' and 'Vee' at: Click on Spanners then on Electrics and finally on Wipers. Good luck - Dave
David DuBois

I was under the impression that all GTs had the later two speed wiring which is 12v from the switch to the motor on red/light-green for slow, on blue/light-green for fast, and from brown/light-green via the switch to red/light-green for parking.

Earlier (roadster) wiring was a ground from the switch to the motor on black/green for slow, on light-green for fast. Park circuitry was internal to the motor.

Four wires at the motor and three at the switch, one of which is a ground, do seem to relate to the early two-speed. even though the colours are wrong. I suggest black/green is the slow speed and red/light-green is the fast, but if slow and fast end up being the wrong way round then it should be a simple matter to change them. The other thing, of course, is that you have a butchered roadster harness in a GT! However if you have an earlier roadster switch and a later GT motor that probably still won't park.
Paul Hunt 2

After reading the above and rereading the wiper sites, I think FR is right. There is not a third brush in the motor. So they must have made a round motor single speed. Interesting that it is a 12W.

Dave. Paul hunts page makes it even more interesting. He says the Red/Lt green wire was not on the 67 but started with the 68 and the Black/Green was not a wiper wire for the 68 on.

He shows the black/green as the slow wiper feed for the 67.

I am going to pull the motor and take pictures tonight.

Now, I would like a two speed motor. Can i use any motor from a later MG and just change to the GT gear?
Bruce Cunha

Bruce, maybe it's a 68 disguised to look like a 67 - dash envy :)
Mike MaGee

I keep telling people that Lucas used MODEL and PART numbers. Model numbers, representing basic designs, are things like 12W, L551, etc. The many variations of Models get part numbers, usually 5 or 6 digit numbers for assemblies, or frequently more digits (like 9), for individual parts. Part numbers never have letters except at the end, where they indicate minor variations.
In the case of wiper motors, Model 14W is the common post 68 motor, and comes in 1 or 2 speed versions. In 2 speed form it has 5 wires in a plug. One speed probably has one wire/terminal missing from the same plug. 12W is a strange thing, evidently used only in 65-67, on cars like the GT and other "upmarket" versions of cars that had previously used the square 3WA or similar. There are lots of diagrams of various square motors and of the 14W, but nothing on the 12W. No doubt 12W came in one or two speed also. Is the 12W a permanent magnet field? If not (ie wound fields), then they may be varying speed by switching in additional field coils, or switching two fields from parallel to series, which are the other ways of changing speed. There won't be a third brush.
There is a diagram of an alternate system for 65-67 cars, but it does not say if that is two speed. Can't imagine what else it would be, and since Paul and I both believe there were two speed systems on early GTs, that must be it. If you post the info I requested above, we can likely sort this out.
FR Millmore

Thanks FR

Here is a web site with pictures of the unit

Here are the details.

What it says on the cover

Park ------->
12W DA
12V 1 67

Four wires. Black, Green, Black/Green and Red/Lt green

Green goes to Right Vertical pin. This goes to motor and to one of the contacts on the gear.

Red/Green is hooked to the other pole of the motor.

Black goes to outside contact and Black/Green is center contact.

Switch is a single throw with 4 terminals. 1,2,4,7. Terminal 2 is black wire. Terminal 4 is black/green and terminal 7 is red/green. 1 is not used.

Solid magnets, two brushes

The gear is marked 115. Full sweep on my GT windshield.

I would be happy to send the photo's if you can use them to come up with a diagram.
Bruce Cunha

My 67 gt has a flip switch on the dash to turn the wipers on and off. No hint of an alternate speed. It is one of the few circuits I haven't messed with.
Barry Parkinson

1) it is a single speed motor.
2) 75580 is evidently unique to GT, pre 68. Another motor 75446 is shown as both Rdst & GT. There is very little part breakdown info on 75580.
3) I find no reference to the 54071398F number - in accordance with the usual system I noted, it is likely the gearbox or case part number.
4) The 75580 would include the gear. The gear number is different by 68, so this gear may be unique to this 12W motor.IE, it may not fit in a 14W 68-on motor
5)There are two switches shown. 34426 and 34889-optional for both rdst & GT. This should be stamped on the switch. My guess is that the optional switch goes with this odd motor.
6)The back of the gearbox is notably different from a 14W, especially the black plastic connector/limit switch piece. On a 2 speed 14W it is white and mounted at an angle, with the three wires that go to the motor proper plugged into the back side of it, but running outside.
7)The different connector/limit switch arrangement could account for the odd gear, since the limit switch engages the backside of the gear.
8)Since the motor is one speed, the single throw switch is correct. And since you had it working on one speed, we are running around in useless circles!!
9) the "optional" diagram I have is similar to Paul's early 2 speed one, but I see no way either could represent a two speed switching setup. My diagram shows a 4 terminal switch numbered 1 through 4, but Paul's only uses 4 terminals anyway. The germane point seems to be that the terminals on the odd side of the switch are tied together internally, so that 1 & 3 (or 1 & 7 on your switch - if it is correct) are electrically identical. This seems typical for different wiper switches on a variety of cars. By your description of the wiring in the motor, RG should go to either of the odd terminals, and BG should go to one even with B on the other even. When the switch is in position to connect RG with B, the armature circuit is complete to ground and the motor runs. When the switch connects RG to BG, the power goes through the armature, switch, and back to the park switch, then to ground via the B off the park switch. This is what you say you have.
10) If you want two speeds, get a 14W With 3 wires running into the motor from the connector block - you can see them. Then we gotta figure out how to wire & switch it-but I have done that! Then you need a 115 gear and it is still possible that the gear from this motor might work, but don't count on it parking right!
FR Millmore

Thanks Much FR

From Barry's post, it appears clear that the GT did have a single speed wiper.

So, if I want to have a two speen, I need to look for a two speed motor from a GT. It would appear my options are to find one of the 67 vintade (12W) or a 14W with a 115 degree gear that I would have to adapt for a sash switch.

From what I am interpreting, a two speed will have 5 wires. Is that a correct assumption? That would make it a bit easier to identify one.

Since I have the single speed working and parking correctly, at least for now I am ok.

Thanks again. Figuring things like this out are part of the fun of owning an MG.

Thanks again.
Bruce Cunha

Perhaps Paul & meself are daft and there were no two speeds before 68. A two speed 12W is probably extremely rare.
A two speed WILL have 5 wires, three of which go into the motor through the notch in the case, which you can see.
Comparing a 2speed 14W in front of me with your pictures, it appears that the brush plate assembly would bolt right in to your motor. The brushes are mounted differently, so the plate is spaced up from the gearbox face to align the brushes with the commutator. The 14W appears to have the requisite spacers cast in, but you could make some. You would then have the 3 motor wires needed, and if you were very clever, could get the additional wire into the empty slot in your connector block and plug. That would leave it all looking original. But I would try switching the gear and using the 14W complete with plug first.
I think that I used a pre68 toggle headlamp switch when I did this, with a jumper to satisfy the requirement for the odd terminals to be electrically equal, as I state in 9) above. The fifth wire would go to another terminal on the even side. I have this all written down somewhere, but it is on paper. I've seen it recently, but chance of finding it is near zero.
FR Millmore

Bruce, I found this article while looking for something else, maybe it will help.

Clifton Gordon

Thanks Clifton. I put it in my favorites. If I go with a newer 2 speed 14W motor, I will use that information.


I am going to purchase a motor off e-bay. I think your thought of putting the brush plate from the 14W in the 12W makes good sense. The wire harness has a space for a 5th wire, so I should be able to make it look good. In looking at a blow up of the 14W in my Hayes manual, they look very close.

One thought/question. I have a three position switch for an MGB(6 poles). I believe it may have been a light switch. Do you know if this would work for the two speed?

Clausager says that the GT only had two wiper blades througout its run. I was under the impression that the 115 degree wheel was used on the GT to cover the different windshield. I wii see if I can find a 14W motor from a GT. Gear may be the 115 degree.
Bruce Cunha

That makes sense because the PO of my GT (Bob Mason) told me the two-speed conversion was from a later GT. If his wiring diagram would help let me know and I will scan it.
Steve Simmons


Please. Sounds like something I can do. I will write up all information and send it for others to use.

Please send to
Bruce Cunha

From the pictures it seems that not only did the GT have a single-speed system, but I'm pretty sure it had the later parking circuitry as well! This is completely opposite to the Workshop Manual which shows a 2-speed motor with the earlier parking system.

Depending on how many spades are on the toggle switch a headlight switch can be used, early ones had spare spades which give the extra functionality for the later wiper parking circuitry. Basically the switches have eight internal contacts in two rows of four. All four on one side are connected together internally. When the switch is in either extreme position the pair of spades at the same end of the switch as the tip of the toggle are connected together, the next pair along are open, the 3rd pair are connected together, and the 4th pair are open. In the middle position all four middle spades are connected together and the two end pairs open. The park wire goes to one end spade and the fast wire to the other end spade. The 12v wire goes next to the park wire and the slow speed wire next to the high. The four linked conenctions have no wire.
Paul Hunt 2


I have a '64 mgb roadster with a single speed wiper motor and I am not concerned with originality, my car is already a mix and match daily driver, so my question is: What wiper motor (any kind) or control unit can I use to give me more, faster, and variable speeds to my wipers? I have a two speed motor off of a '72 with three wiper blades; is that of any use to me? Thank you in advance.


Charles Campbell

Yes, but you will need a suitable 3-position switch as above and need to wire it as per the later power and parking arrangements. Ignore the three-blades issue, but if it is off a GT (probably not if it is a 3-blader) it will probably have the wrong arc/sweep. I also don't know whether the early rack and tube will connect to the later motor, if not and you have the 3-blade tube and spindles you can probably codge something up from those, even if it means the middle spindle is upside down under the panel and doing nothing.
Paul Hunt 2

At this point, I left the single speed in the GT. It works nicely since I cleaned all the thick grease out of it and the wheel boxes. It parks very nicely and actually moves at a pretty good pace. I will time it and get the results.

We must have a number of 67 or earlier GT's out there. Does anyone have a 12W that is two speed? If so, can they give some information on the numbers on the unit and the switch they have.

It would be good for clarification.
Bruce Cunha

This thread was discussed between 16/09/2005 and 28/09/2005

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