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MG MGB Technical - Windshield Washer Motor

Hi all,

The windshield washer motor on our 70 B has taken to running all the time. As soon as the key is turned on, it starts buzzing. Pressing the washer switch seems to change to tone a bit but the unit keeps running.

Appears to be a solid green wire coming in with 12 volts at all times and a white/green leaving that must be the ground side.

I've checked the archives but turned up nothing to match this one.

Maybe it's the last name that's bringing out the electrical gremlins, but I invite your thoughts.


Joe Lucas
Joe Lucas Manitoba

Hi Joe.

There should be 12V on the green wire (with the ignition on), the other side of the pump (light green / black wire, according to haynes) should be connected to earth when the button is pushed.

I would check for a problem in the switch or chafing of the wire's insulation on a sharp edge somewhere.

Don
Don

Hi Joe,

Try going to the 'Electrical Help section from the opening page of MGB Technical in this BBS. Then look at wipers. There is then an option to look at washers. This may help.

Good luck

Peter
P L Hills

Don - I'm more of a mechanical guy myself but it sounds like I'm into the wiring stuff on the weekend. Thanks for the direction.

Peter - Thank you for the "Electrical Help" advice. I didn't know that information was even there. This new tech support will certainly come in handy in the future.....as well as for weekend's adventure.

Thanks both,

Joe
Joe Lucas Manitoba

I think the park switch has stopped working. It's located by the gearbox section of the motor. The back of the white plastic gearwheel operates a plunger which activates the switch. Part of it could be worn or the contacts might have welded together. HTHs
Barrie E
Barrie Egerton

Sorry, misread the thread. thought it was the windshield wiper motor. Barrie E
Barrie Egerton

Barrie - thanks for the thought. I've been scratching my head over this silly problem for a bit now & just waiting for some plastic glue to dry before putting the steering column cover back on and trying things out.

There appears to be 12 volts at the pump and it's grounded out by pushing the washer button. I've always thought that the power would come to the switch first and then be run to the powered device. Is this typical for these great little cars?

Joe
Joe Lucas Manitoba

Joe,
The wires should be Green power, and Light Green/Black to the switch. Some cars are shown as Green/PinK for power. Don't know where a White/Green comes from; later cars have a W/G under dash for a radio, and later cars have a W/LG for ballast resistor start bypass, but 70 shouldn't have either. All with pumps show a LG/B to the washer switch.
Whoops! The cars ("some territories") shown as G/K feed have a W/G from the ign switch to a line fuse, whence it emerges as G/K to a four-way connector, then one of the G/K goes to the pump. The other G/Ks feed the heater blower, radio, and wiper motor - in other words, they took some of the load off the Wite/Green fuse circuit and put it through the line fuse. Whatever, something on your car is either changed or one of several known "not-on-any-diagram" things. W, G, W/G, or G/K should always mean power - controlled by the key and fused or not, and anything with B as a tracer is always going to ground, generally through a switch or sensor.
It is common to switch ground on some things. If there is already power in the vicinity, you only have to run one wire to the switch, and if that wire should short out along the way, it just turns the item ON instead of blowing something up.
FRM
FR Millmore

FRM.....

Things are really confusing me now - not your description, but the operation of this pump. I have 12 volts coming in on the green, just as you describe and light green/blacke to the switch bigh, again as you have accurately predicted.

Pull the switch wire off the pump & check continuity and there is nothing taking it to ground. Plug the wire in and the motor starts to run very weakly. Push the washer switch and motor goes to high speed.

With my infinite knowledge of electricity (which I used up making my morning coffee) I'm thinking that a small leak to ground might have developed - but not detectable on the ohm meter.

If that makes sense, then it should be a "simple" matter of tracing the light green/black through the dashboard twilight zone to find the leak....what does a pool of electrons look like?

Back to the under-dash yoga position........Joe
Joe Lucas Manitoba

Joe,
I have gone back to making coffee with a percolator on a gas stove - best to keep electrickery away from that which you ingest! So now you want to undo the rare two-speed pisser pump? Not many of them were made.
Enuf tomfoolery!
"a small leak to ground might have developed" -exactly. "- but not detectable on the ohm meter." If you are using a digital meter, I have found that they frequently won't read anything if they are out of range, try switching ranges. Analog ones are better for testing in my experience. From your description, there IS a partial short to ground.
The only place you will find the LG/B wire is at the connectors to the switch harness at the column. Disconnect the plug or bullet connector there and see what happens. Most likely place for trouble is inside the plastic cowling; disconnecting that connector should eliminate the wire in the harness. Functionally, the push switch connects LG/B to a B, which goes to ground as B always does.
FRM
*"electrickery" courtesy of Bill on the Spridget board
* A pool of electrons looks like zillions of little $$ signs under magnification. Very volatile and evaporates quickly.
FR Millmore

FRM,
Electrickery....love it!

It's certainly been a day of electrickery and your latest note was exactly correct. I found the plug that connects the column harness to the dash wiring and unplugged it - the problem stopped making the column harness the likely candidate. I pulled it out, took the switch apart, spent 20 minutes finding the ball bearing that took off on me. Pretty simple set up but no obvious shorts. I pulled off all the black tape, separated all the wires and plugged it back into the car - no problem at all.

Pulled it off again, examined every inch of wire and could find nothing. Retaped everything tight, reinstalled and everything is now working properly. Maybe it just wanted a little attention to feel better about itself? Your note about the ohm meter is noted. I've been using a new digital unit that replaced my old analog unit (just because it looked cool and gave clear numbers) - and it appears that I've gone the wrong way. I'll pick up a new analog unit and go back to the old ways and hopefully avoid losing small numbers in the future.

Many thanks to my wise guys who got me through this. I wish I could offer advise to the next person with this problem but we are dealing with Spridget Bill's electrickery and just have to sweat through it.

Regards, Joe
Joe Lucas Manitoba


Hey Joe Lucas

Are you related to the "Prince Of Darkness" ?

... just kidding

Where are you from in Manitoba ?

I worked in Swan River a couple of years ago

Nice place with great people there

Good luck with that washer pump

MG
M Gaudreault

MG

You gotta be kidding! You've got some fantastic initials there but "MG & Lucas"....sounds like a recipe for disaster.

Swan River is quite a way from my home in Winnipeg, but pretty close to my favourite escape, Riding Mountain Nat Park. Just like in your present home province, we are blessed with some pretty great people here and I'm glad you enjoyed your time with us.

Strangely, the Prince of Darkness usually puts me out of service, but this problem kept the pump constantly running - some kind of reverse spell this time.

Keep well,

Joe
Joe Lucas Manitoba


"Swan River is quite a way from my home in Winnipeg"

You bet! I landed at Winipeg airport using airport transfers tonbridge and drove to Swan River several times from October to February when I worked there (5 hour ride). Great road especially across the Lake Manitoba (or is it Lake Winipeg ?)... when the weather is fair.

Bye
M Gaudreault

This thread was discussed between 12/08/2005 and 17/08/2005

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