Wiper motor wiring

A popular modification for early Sprites and Midgets is to replace the single speed wiper motor with a dual speed motor from a later model car. While it’s relatively easy to wire up a switch for the two speeds, getting the wiper motor to auto park when the switch is turned off can be a little more tricky.

These notes document how I wired up a 2 speed wiper motor as found in a 1971 US specification MG Midget. As wiring can and does vary between models, as well as previous owner modifications, any modifications you attempt to make to the wiring of your car based on these notes are entirely at your own risk. Beware, Electrical faults can cause fires.

I haven’t dismantled a wiper motor, so I don’t know for sure how the motor is wired up internally, but several hours of studying a worksop manual and the wiring diagram of a 1971 US spec. Midget with 2 speed wipers and a lot of trial and error eventually revealed the secret of the wiper motor auto park circuit. We are now talking real Lucas Prince of Darkness stuff here!

What I found was that the auto park wire on the wiper motor could only be connected when the slow and fast speed wires were off. When you supplied power to either slow or fast, you had to disconnect the auto park lead otherwise there was a certain point in the wiper motors cycle where the auto park lead temporarily shorted to ground. I would imagine that if you left it permanently connected the auto park switch/mechanism inside the wiper motor would eventually destroy itself.

Using a cheap OFF/ON/ON toggle switch and and a relay (Hella 3057 12V 40/15A) it’s relatively simple to get both wiper speeds and the wiper auto park to work. The switch I use looks reasonably close in appearance to the original Lucas dashboard switches. I didn’t have a spare headlight switch to try with this circuit so sorry folks, I can’t tell you if it would work or not. (If anyone does try this let me know and I’ll update these notes accordingly.)

I solder all of my connections, covering the joints with heat shrink spaghetti, then for neatness finish by binding up the wiring with electrical tape. I have a pet hate of those quick crimp wire connectors as they can corrode and cause poor electrical connections.

On first inspection this circuit looks like it can’t work, but does as you’ll see in my explain a little later.

I’ve tried to include the wire colours that appear in the workshop manual wiring diagram, if you can get part of the original wiring loom with the wiper motor, this makes it easier.

RLG – Red Light Green, NLG – Brown Light Green, ULG – Blue Light Green, GK – Green Pink.

Also note, I haven’t drawn the Wiper Motor connections in the above diagram as they actually appear on the motor (as a double row), but instead to make the above diagram easier to read.

The pin connections on the Wiper Motor are as follows:

1 – Earth 2 – Auto Park switch 3 – Fast 4 – Auto Park  +ve supply 5 – Slow

HOW DOES IT WORK

Flicking the toggle switch to the first position (slow operation), power is applied to the relay, closing the contact and supplying power to pin 5 on the wiper motor (via pin 87 and 30 on the relay). The Auto Park connection on the Wiper Motor (pin 2) is not connected to anything while the relay is energised.

Flicking the toggle switch to the second position (fast operation), power is supplied directly to pin 3 on the Wiper Motor. At this point you might expect the relay to turn off, but in fact the relay remains turned on by current leaking back out of pin 5 (slow) of the wiper motor (via pin 30 and 87 of the relay). The Auto Park connection on the Wiper Motor (pin 2) is not connected to anything while the relay remains energised.

Flcking the switch to off, causes the relay to turn off, this connects pin 2 of the Wiper Motor to pin 5 of the Wiper Motor (via pin 87a and 30 of the relay). What I think happens here is that power is connected to pin 4 of the Wiper Motor, this must be internally connected to pin 2 via a switch, which allows us to continue to supply power to the slow pin 5 of the motor until it reaches the park position when pin 2 turns itself off.

POSSIBLE ENHANCEMENTS

Although I haven’t done this yet, one obvious enhancement that can be easily made to this circuit is the addition of intermittent wiper operation.

The simplest way would be to connect a momentary push button switch from the +ve supply to the slow wire of the toggle switch (or pin 86, or 87 of the relay). Just press the button for a single sweep of the wiper blades.

Taking this one step further you could add a simple electronic timer circuit to turn the relay on at say 10 to 15 second intervals. You would probably want to replace the toggle switch with a rotary switch that had multiple positions so you could then setup the switch  to have: Off – Intermittent – Slow – Fast.

This article may be reproduced for non-commercial purposes only, and full credit given to the author, Eriks Skinkis.

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The Jenny Craig effect

Well Folks I thought that I should post a few pictures of the car now that she is back on the road. The weight is now 630kg with half a tank of fuel which means that I have managed to ’save” a whopping 63kg during the course of the rebuild.

Damn fore shortening with wide angle lenses!

I love this angle

Evening splendour

The windscreen is angled back to 45 degrees

Long and lean and easy on the draw....

the hood scoop looks so much better than the previous bulge

I was undecided about the nose cone colour but eventually chose silver.

Cheers Comrades

INTERIOR DONE

i HAVE PAINTED THE HOOD SCOOP SILVER SINCE TAKING THIS PICTURE

LONG AND LEAN

THOSE SEATS ARE VERY COMFY

ARMCHAIR COMFORT

SO CLOSE THAT I CAN ALMOST FEEL THE WIND IN MY HAIR

KEEPING IT POLISHED WILL TAKE LOTS OF WORK

Latest pictures

Dash instruments and bonnet

seats are made from the back seat from an EA Falcon

the transmission tunnel has a well padded arm rest

it weigh a little more than the fiberglass bonnet on MK 1 but it looks SO much better and it is hinged to make checking the oil or water easier

sleek or what?

the dash is seen here with the opening fro the glove box unfinsished

with a suitable prop the bonnet looks great.

The bonnet is lovely and shiney but will require a bulge to clear the front of the cam cover

starting to look like a Seven now

driver’s side

looking towards the front

3/4 rear

new scuttle is slightly deeper than the old because the dash angle has been reduced.

scuttle clad

Red and silver is a great combination

Some pictures of my progress.

Chassis now painted “delicious red”

Wipers and a very nice rear quarter

the wiper motor just needs a mounting strap and the arms need to be shortenedby about 75mm

The winscreen wipers were easier to set up than I expected.

the curved tubes give a very nice line to the rear quarters

I had the good fortune to find a metal sun chair with a circular base which was the right diameter to make the rounded section at the rear of the cockpit.

The curved tubes at the rear of cockpit will be clad in 1.6mm ally

the fuel tank is to mount lower in this frame so it will sit on the two pieces of angle which I have welded into the the rear of the frame.Also in this photo is the fuel pump mounting bracket.

Some photos of my latest progress

Enjoy

Cheers Comrade s

Some pictures of my new chassis

starting on a sheet of 19mm MDF the bottom frame was laid out and built up as per the book except that the frame is 50mm wider and 25mm higher

cockpit side rails are 25mm ERW tube to give a nicer rounded edge

those open tubes in the bottom of the transmission tunnel

round tube at the top and the bottom of the front section

An auto requires a large opening

the battery will sit at the bottom of the frame for a lower the centere of gravity

an extra cross tube for strength at the bottom of the picture

looking like a seven frame now

from the front

seet belt retractors will fit inside this 100×100 RHS

the cockpt scuttle is part of the frame proper rather than being bolted to it.

engine bay bracing

making the corners rounded

windscreen frame is made of 2O x 20 RHS and it fits into sockets in the scuttle

hand brake location on the top of the transmission tunnel is awful in practice as it gets in the way of the drivers elbow while driving. My solution is to move it to the passenger side of the transmission tunnel

to ensure the engine/trans will go in the right place I had to allow for some postioning adjustment so the gear box mount will be apiece of 3mm sheet that bolts to these tags

looking forward and you can see that the rear bulk head is higher and drilled fro the head rests

rounding off the corners

the trans tunnel is made of folded 1.6 mm steel this makes the whole kit and kaboodle much narrower than in the book .Also it is lower at the front.

being an auto there is no need to have the shift lever that far back

Roomy! for a seven

rather than re use my fiber glass bonnet/ hood I am going to use alloy sheet to cover the engine also I have decided to hinge it on the drivers side using the over center clips on the left to hold it closed this requires a frame which I have made from 13mm RHS

The bonnet/ hood frame in the open position I will have to make some kind of folding retainer

the section of the trans tunnel under the dash has a removable top for acess and mountying the shifter to

I went out and bought a spare master cylinder so that I can set up the brakes this time I am ditching the booster and the lpedal is to be set up to give the best possible lever ratio

this shows all of the little bits added to give the right shape to the scuttle

Rather than have individual mounts for the rear suspension links I made each side from one piece of 50 x 50 x 3mm RHS

reinforcing gussets for seat belt mounts

Coming together

Well after a couple of days swinging the grinder and stoking up the Mig I have got the main part of the chassis together. I spent most of yesterday working on laying out the floor tubes and the outline of the transmission tunnel.

My cunning plan is to run the fuel lines through the tubes on the left hand side of the base of the transmission tunnel and the brake line and rear of the car wiring  through the one on the right. This has necessitated some minor revisions to the tube layout (so the longitudinal tubes are continuous ) but I now have it all laid out and tacked together.

I want to have the heavy battery cited as low as possible to make the center of gravity as low as possible . to achive this I have shortened the  passenger side footwell by about ten inches and teh battery will now reside down in what was perviously wasted space.

I had a strole of luck finding a piece of 100 x 100 x 3mm RHS as my plan is to put two sections in place of the 1oo x 1oo pieces of 3mm plate at the top of the rear shock mountings this will allow me to mount the seat belt retractors in a more desirable position and provide a good posotion to attach the rollover bar hopefully with a conceled fixing  ( a single M12 bolt from below on each side ) this will also raise the real deck a little which should improve the proportions of the car and give a little more space in the boot as well.

I will post some pictures later today after i have done some more welding Today I plan to make the framing for the dash and scuttle

Cheers Comrades

The big plan

Once you have finished a project like building a car there quite naturally comes a time when you are all too aware of the parts of the design that are really not quite right. The little things that niggle at you. All of my fellow builders out there will know exactly what I mean but for the benefit of new builders or those who have yet to start I’ll list some of the issues that I hope to address.

Ergonomics:

There are a few issues with the control layout , the steering wheel is too low for a start I reckon that it needs to be at least two inches higher and it could also be between two and three inches closer to the dashboard.

Instruments and Dashboard

A great find on Ebay UK which cost only $25 aud (including postage) which is great for a brand new in box instrument.

While the current set up using the original instrument cluster from my engine donor works OK I am rather unhappy with appearance of the dash and the tacho has never worked anyway so I was faced with a dilemma either get another cluster and live with the aesthetics or get rid of the cluster and  fit individual instruments . As my car has an automatic transmission and  a rev limiter I really can’t see that there is any good reason at all to have  a tacho.  So I will be going for the absolute minimum in instruments   speedo, temperature and fuel along with warning lights for ignition high beam and turn signals and to that end I have bought  a speedo that I found on Ebay. I just have to find a suitable fuel and temperature gauges  which will probably be fitted in this pattern     oOo  in the centre of the dashboard .

Ignition switch

The current location on the steering column is not viable if I want to move the steering wheel closer to the dash so I will be mounting it so that it fits in the dash itself  probably between the instruments and the steering wheel . Because  of the way it mounts I will have to make a suitable bracket but this is a small price to pay for retaining the  coded key  immobiliser.

The handbrake leaver

This really annoys me because it sits exactly where my elbow wants to be. I want to relocate it to the passenger side of the transmission tunnel where it will still be easy to operate but well out of the way
The transmission tunnel could be a fair bit smaller especially if it were made from folded steel rather than the present RHS tube structure without compromising the strength of the chassis.

Engine bay:

The way the engine requires a large bulge in the bonnet really gives me the hump and spoils the look of the car.

Roll-over bar

Although not actually required by law for a road car I have one fitted but I would like it to be a few inches higher.

Centre of gravity issues

These cars do have a very low centre of gravity but there are always way that it could be made better , for instance by ensuring that the heavy battery is mounted as low as possible  and that  the fuel tank is  mounted as low as possible .

Weight:

I know that I have made the car too heavy by overdoing a few things and I expect to be able to give the car a serious diet. I think between 40 and 50 kg should be very possible without the use of any exotic materials. I am taking to heart the Colin Chapman philosophy of adding lightness.

OK  that is a lot of things to deal with and after a great deal of thought I have decided the best way to address all of the issues is to build a new space frame that incorporates all of the improvements on my list above but more about that later.