Wiper wiring query.....non-functioning wipers

So, first issue to be dealt with....wipers. 1988 90, 200Tdi conversion.

Previous owner reported that starting a couple of weeks ago, when activating the wipers, the fuse would blow!

Having done a bit a research, it would appear this is a common issue!

Some report it is the parking switch at fault, a stalled/stuck motor or damaged wiring.

Last night while I had her in the workshop at work taking a look, I unplugged the motor, isolated the vehicle battery and to check for a short to earth, I metered from the green wire to the black wire on the plug while the plug was disconnected and there was continuity! Is this correct.

Looking at the wiring diagrams I have found, it would seem that there is a fused supply to the steering column switch pack, this then splices off to the wiper motor and also to the reverse light switch.

A selection of other wires go to the wiper motor which I assume are, fast, slow, and intermittent....

So could I ask if anyone can confirm if this continuity between Green and Black on the wiper motor plug when unplugged and battery off is correct...and also how the system works....i.e. Power to motor on Green, Earth on Black....but I am not sure how the switch side of things works to get the motor to run!

Any clues would be a great help!

I hate electrics! I don't think you should be getting continuity across any of the greens and the black, providing the switch is definitely off. Might be a dodgy switch/ wiring around switch, dodgy connections behind fuses ( do you have the glass fuses? I do and they caused all sorts of problems to begin with including wipers, changed all of them for new and cleaned all the holders and sorted all the gremlins!

bluedog333 said:

I hate electrics! I don't think you should be getting continuity across any of the greens and the black, providing the switch is definitely off. Might be a dodgy switch/ wiring around switch, dodgy connections behind fuses ( do you have the glass fuses? I do and they caused all sorts of problems to begin with including wipers, changed all of them for new and cleaned all the holders and sorted all the gremlins!

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She is fitted with blade fuses, I was surprised to see continuity from Green to Black...the plug was disconnected from the motor and the battery was also disconnected which I thought was a tad strange!!

not sure on the operation logic of how the park switch and motor power works, as the diagrams are not clear....first test would be to bench test the motor, but I am not sure which terminals to apply power too...(negative is a bit obvious) but if it gets a live supply from the Green Wire, how does the motor run, i.e. where else to I apply power too to run the motor!? confused.com!

I was a pikey when I checked mine, I connect negative and then applied live to the others one at a time, didn't know what I was doing (still don't!) but the motor worked so I knew that wasn't the fault!

Saint.V8 said:

She is fitted with blade fuses, I was surprised to see continuity from Green to Black...the plug was disconnected from the motor and the battery was also disconnected which I thought was a tad strange!!

not sure on the operation logic of how the park switch and motor power works, as the diagrams are not clear....first test would be to bench test the motor, but I am not sure which terminals to apply power too...(negative is a bit obvious) but if it gets a live supply from the Green Wire, how does the motor run, i.e. where else to I apply power too to run the motor!? confused.com!

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Don't know if it will help you but the early wipers had a permanently live circular contact with a wiper driven round it. There would be a small break in the circle and the switch would power this small section so that the wiper would move and connect with the main ring and power it until it arrived back at the break. If the switch was still closed then the wipers would continue.

or am I just showing my age

bluedog333 said:

I was a pikey when I checked mine, I connect negative and then applied live to the others one at a time, didn't know what I was doing (still don't!) but the motor worked so I knew that wasn't the fault!

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Considering I almost fused the car last night whilst trying to figure out how the hell the PO had wired the lighter socket (two wires for a lighter socket and he managed to balls that up!!) I would rather not try that method of fault finding but the principle I will adopt!

dogsbody said:

Don't know if it will help you but the early wipers had a permanently live circular contact with a wiper driven round it. There would be a small break in the circle and the switch would power this small section so that the wiper would move and connect with the main ring and power it until it arrived back at the break. If the switch was still closed then the wipers would continue.

or am I just showing my age

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Think you might be showing your age....

Found the attached diagram which offers a little more insight into the switch logic....albeit for a later model with a delay timer/ECU thingy....

My theory is, disconnect the multiplug, and provide an earth, then add power to the RLG wire (slow wipe speed) and see if the motor runs...this should bypass the park switch....wire this to a fuse and a switch for on/off control until I figure the original problem. Just have to manually time when to turn it off for parking the wipers!

Well that's the theory anyway!

Firstly, your continuity between the green wire and the black. Even with the battery out, there are multiple ways for this to be true. Door courtesy switch and interior light, for example.

Given that old Landies attract Scotchblocks and mouldy insulating tape, I'd bet on a wiring fault over a motor short.

To test the wiring for shorts, re-connect the battery and operate the wiper switch in all modes. If the fuse blows with the motor out you know where the problem is.

The working part of the motor has three wires. Earth, fast+ and slow+. The fast and slow are two separate brushes, the fast being opposite the earth brush, and the slow at some point in between. Both fast and slow get the full 12v input, it's the brush position that controls speed.

To test the motor connect to earth and then 12V to the fast or slow in turn. That will test for turning, but if you do have an internal fault you'll probably get a big spark. If you like you can put a suitable Ammeter in between and see if you're using a sensible current or have a short. You could use a fuse if you don't have a meter.

The park switch is correctly described by dogsbody, and unlikely to be the problem. Ditto the intermittent which uses the same contact.

Just fixed my wipers recently with a similar issue. Wiper fuse would blow as soon as wipers turned on. One of the wheel boxes was seized so the motor couldn't move, overloading the circuit. Have you tried removing the motor with the wiper cable at all? If you can't pull it out then it's probably a seized wheel box. Water had got into the spindle and rusted it over time.

Many thanks chaps for the great information, I have temporarly wired the RLG wire to a new fused and switched live to get the wipers working for now. I will take the comments on board and have a good old goosey when it warms up a bit.

Motor certainly works well and the spindle drive boxes seem to work freely.

Just curious that when checking the multiplug with it disconnected there is continuity from the Green to the Black, which would mean there is a dead short somewhere up the line somewhere!!

With plug detached, I placed a new fuse in the line and with a puff it was out again, so definitely a short in the wiring....good thing reverse lights aren't part of the MOT or a legal requirement!

Still, I will sort the reverse lamp situation out in due course....

Next up is intermittent brake lights!

Saint.V8 said:

Next up is intermittent brake lights!

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In my day these used to work by having a spike under the brake pedal. Pressing the pedal would push the spike into the backside of a small dinosaur strapped back to front under the car. The dino would get ****ed off and his eyes would glow red.

Don't even ask about semaphore indicators . . . . .

dogsbody said:

In my day these used to work by having a spike under the brake pedal. Pressing the pedal would push the spike into the backside of a small dinosaur strapped back to front under the car. The dino would get ****ed off and his eyes would glow red.



Don't even ask about semaphore indicators . . . . .

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Have you been drinking?😳

bluedog333 said:

Have you been drinking?😳

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No

Must be something in the water in the West Country!