Wiper motor miswiring?

[Fingolfin]

Something very very curious for you all this time. At least I think it's curious. I'll offer you all the details, so this'll be a long post.

A week ago, I was doing Mog's wiper motor circuit; I'd set the 'main' circuit up previously, and was working on getting the self-park mechanism to work correctly. I managed the feat, and the wipers worked beautifully, sweeping up and down the screen at a rate of roughly one full sweep per second, and self-parking in the right spot. This is a '59 with the 'clap-hands' wipers, by the way.

Fast forward to three days ago. In the intervening time, I had proceeded to connect the dynamo, coil, distributor, oil pressure warning light switch, the horns, and part of the tachometer wiring; I was unable to fire the engine yet, so I was only sure the oil pressure warning light was working correctly (the light lit up when the key was turned). I decided to try the wipers again, because they're fun to watch, and -- nothing! The ammeter showed a short, so like a flash I disconnected the battery and inspected the motor; the small wire from the motor box to the self-park dome was quite hot. I inspected inside, and there appeared to be no issues.

Scratching my head, I put the battery back on and tried the circuit again (using 20 amp fuses, to be safe from a short). The wipers moved sluggishly up the screen and stopped halfway up. Circuit off and back on, no movement. I assisted the wipers through the rest of their sweep and turned it back on, and they moved slowly back down to the park position, then back up, and stopped in the same place. The most curious thing was, the wiper circuit showed some life (slight movement) whether the key was on or off, and what's more the oil pressure warning light glowed dimly whenever the wiper circuit was on.

I decided some of the new additions to the wiring might be fouling the circuit, so I disconnected the oil pressure warning light first, and tried the wipers again; they moved through a full sweep at normal speed, then stubbornly stopped again halfway up the screen. I disconnected all the rest of the new circuits, but this made no difference; the wipers remain stopped.

I used my circuit testing light on the wiper circuit. The three wires leading to the motor (green, black/green, and black) were all live, regardless of the switch being on or off. The self-park wire was also permanently live. I inspected behind the dash, and it appeared that the switch was wired correctly.

So, my question is of course what's gone wrong? I'm also curious why the wipers functioned so well before, and then gave up, though I made no modification (that I can tell) to the wiper circuit in the intervening time.

Wiring was going so well...

[mike.perry]

Did you wet the screen before using the wipers?
Test the motor by disconnecting the terminals and connecting them direct to a battery. The black and black/green should both be earthed to the same terminal of the battery

[JOWETTJAVELIN]

Battery fully charged?

Check all earths then if still no joy remove the wiper motor and test it on its own.

I am no auto electrician but the fact the oil lamp is only glowing very dimly would suggest something is amiss elsewhere in the circuit.

If a fuse has blown then something is shorting: find it and rectify it. DO NOT bridge the fuse contacts with a nail or similar.

[bmcecosse]

Obviously major wrong connections if the wiper circuit shows life with the key off...... Yes - it should continue to park position if you switch off, but Ign key off should cut the circuits dead. So I would start the search there...... Have you printed off a copy of Barry's excellent simplified/colour coded diagram at the head of this section?? Follow this and you really can't go wrong.

[Fingolfin]

Thanks everyone. I charged the battery fully the night before the wipers malfunctioned. I have not had a fuse blow, and I've seen enough smoke in my life to know not to go around the fuse. I followed Mike's suggestion of connecting the number 2 (green) terminal to live and the number one (black/green) and earth (black) terminals directly to the battery, and the results were not promising at all -- the wiper blades moved at a normal pace, but the motor emitted large amounts of smoke! I instantly pulled the wires away and have not tried again.

I will print off Barry's diagram -- thus far I've been using the diagrams in the Haynes and Workshop manuals, which are all in black, so easy to mess up. Also, I have only wetted the screen once while the wipers have been on -- the blades moved so well that I thought there would be no problem...can one of these motors be so fragile?

[JOWETTJAVELIN]

You can rebuild wiper motors - strip it down, clean it, new brushes, oil it etc.

Check the windings for stray wire.

[Fingolfin]

I've already done that -- at least, I've had all the components apart, cleaned them, relubricated them, and inspected their quality. The brushes were excellent. But obviously something has gone wrong...I'll inspect it in the coming days.

[Fingolfin]

I removed the motor from the car, opened up the 'motor' part of the motor, cleaned (sanded with fine paper) all the surfaces that bear on each other, made sure there was a path for earthing through the casing, reassembled the motor, and tested it on the battery (but still off the car) with the wheelbox cover off; the motor worked perfectly. I then placed the cover back on, and it worked perfectly again, with no smoke!

So that eliminates the motor as the trouble. The next step is to ensure the wiring is all correct, and then remount the motor and try the circuit.

[Fingolfin]

The problem was extremely obvious, in the end, and had I simply bothered to look I could've saved myself a lot of trouble. What happened was I had not tightened down one of the terminals on the wiper switch quite enough, and the green/black wire had come loose. Motor and circuit now work beautifully. Thanks all!

[bmcecosse]

Geeeeeeeeeeeeeeezzzzzzzzzzzzzz.

[kennatt]

well I've never done that well maybe once or ten