Indicators not working and Positive earth

[Heuer]

It is a complex system. The motor is always live but there are two supplies - one for the armature and one for the coil. Green carries 12V to the armature, red takes that to the earth via the limit switch. Blue carries 12v to the coil and then you have the two speed circuit plus the motor reverses momentarily before parking. Best to get the motor on the bench and test with a multimeter. Near in mind the resistances are very low so whilst you may assume wires are going to earth they may not be.

The two points of failure are the brush armature and the coil. A brush can fail but that is unlikely to blow a fuse and the coil is more likely to go open circuit which should not blow a fuse.

[Tony]

David,
The two wires going to earth are the green which serves the armature and the blue which serves the coil. Should these wires be earthing.

It looks like my only option is to take out the motor and try and bench test it. I should really send it away but I hate giving up. It's the only way to learn.

Thank you for your help


Tony

[Heuer]

OK. Before pulling anything apart please disconnect all five motor wires from the 5 way connector. Turn on the ignition and see if the fuse blows. If it does we know the fault is with the loom wiring. If not the motor is at fault.

One thing I am not clear about - does the fuse blow before the wiper switch is operated i.e. off as soon as you turn on the ignition? Also is your car +ve or -ve earth?



As you can see from the diagram you should have 12V on the green wire with ignition on. The red wire goes to the park switch which will earth when operated. You should also see 12V on Blue and Brown when the motor is connected.

With the motor disconnected you can test the field coil and resistor.

Multimeter set to measure ohms:

Yellow and Brown wires = ~10 ohms
Brown and White wires = ~ 9 ohms

Please report back and we will go from there.

[Tony]

David, excellent, I have disconnected all the wires from the motor and the switch and checked if any run to earth, and they all have continuity. However I will reconnect them all and see if the fuse blows, I will report back for the next stage when complete. Thank you

Tony

[Tony]

David, I will try and answer you questions in the order they were asked.

1. With the the motor wires disconnected and the ignition turned on the fuse does not blow what ever the position of the wiper switch.

2. My car is positive earth.

3. There is 12v on the green wire with the ignition on.

4. With the motor disconnected I get the following results

Yellow and brown wires = 10.8 ohms
Brown and white wires = 8.9 ohms

5. With all the wires connected and ignition turned on I get

12v on the green wire
12v on the red wire
12v on the blue wire
12v on the brown wire

PS: As my multi meter and the new one I bought insist on showing 25 volts across the terminals I have used a test bulb from the wires to earth(body) and assuming I am getting 12 volts if the bulb lights up brightly)

6. For some reason now when the all the wires are connected, the ignition turned on and the switch in all positions, the fuse is not blowing but the wipers do not work.
(I am presuming I do not need the engine running for the wipers to work)

regards

Tony

[Heuer]

Odd the fuse is no longer blowing but at least you have progress.

Next test is to disconnect the red motor wire and touch it to earth (ignition on, wiper switch off) and you should get a single sweep of the wipers.

[Tony]

David,

Red wire disconnected, Ignition on, switch off . No single wipe.

Tony

[Heuer]

You did earth the motor end red wire, either to the motor body or adjacent bolt?

My guess is you need to replace the brushes - Lucas part 729367 e.g.:
https://www.holden.co.uk/p/lucas-wiper- ... -17h5396-1

[Tony]

Sorry, yes i earthed it to the body in a few places but nothing happened.i should have been mote clear.

Tony

[Tony]

I have started to take of the wiper motor and will be careful when pulling off the infamous clip. I have put metal glue on the end of a rod and stuck it onto the clip in the hope it will stop the clip falling into the abyss. I will stuff cloth in as a back up. I will let you know if it works. I will do a bench test when the motor is off just to make sure it is broken. I will then decide if i send it away or try to renew the bushes.

On the bench test what wires do i need to connect. Would i be correct that i connect the green wire to the negative side and the red wire to the plus.

Thanks again David for the time you have spent helping me.

Tony

[Tony]

Finally managed to remove the wiper motor without losing the infamous clip into the abyss. Upon opening the motor I found the brush failing about as apparently there is a little spring that hold the brushes against the the armature. I found the spring, one broken insulated lug that holds the spring to the brush arm and still to find the other. So I have bought an original Lucas service kits on eBay for £28 that includes all the bits and see what happens when they are fixed in.

I have found a topic from Christopher Storey on how to bench test the motor when all the new bits are in. We will then see if I have any other problems with the motor. I was wonder it an elastic band between the brush arms would work for the bench test in the short term.

I believe there is a thermal cut out switch in there somewhere. Could this have been blown with brushes flopping about in the casing. I did not notice any insulation on the long fixing screws. Can these be wrapped in insulation tape to avoid any shorting issues.

I will post some pictures for any other intrepid travellers who intend to travel this route in the future.

On a slightly different note, when I search wiper motor I do not seem to get all the topic on the subject and I am then surprised when searching the net, lots of items relating to this which were generated originally on the forum. Am I using the search facility correctly.

[Heuer]

I have found a topic from Christopher Storey on how to bench test the motor when all the new bits are in. We will then see if I have any other problems with the motor. I was wonder it an elastic band between the brush arms would work for the bench test in the short term.

Not really as the heat from the motor may destroy the rubber band and you could end up with other problems. Suggest you reassemble the motor using all the correct parts and test.

I believe there is a thermal cut out switch in there somewhere. Could this have been blown with brushes flopping about in the casing. I did not notice any insulation on the long fixing screws. Can these be wrapped in insulation tape to avoid any shorting issues.

The thermal cutout was only present on earlier versions of the motor. Check the Lucas number stamped on the casing - 75404D and 75404E have the cutout 75404F and subsequent do not. It is a thermal cut out which responds to heat and should reset one the heat is gone - based on a bi-metallic strip like the Otter switch.

On a slightly different note, when I search wiper motor I do not seem to get all the topic on the subject and I am then surprised when searching the net, lots of items relating to this which were generated originally on the forum. Am I using the search facility correctly.

We can't compete with the power of the Google, DuckDuckGo, Bing etc search algorithms! However if you search serially our search works very well e.g search for 'Wiper' then search the presented results for 'Motor' then 'Repair' etc. The one advantage we have over the search bots is that they can only access certain areas of the Forum (that I have allowed them to ) so cannot provide a comprehensive set of results.

On a separate note I can highly recommend the DuckDuckGo search engine as unlike Google it does not present you with adverts, does not track your every movement and does not sell that data to anyone who wants it. https://duckduckgo.com/ You can make it the default search in any browser

[Tony]

Hi David,

Just to be different mine Is 75403D. Do you think It would have a thermal cutout.

1B1132EB-A11B-4C2A-AD38-4F8C6717CC77.jpeg (27.25 KiB) Viewed 7243 times

In terms of the elastic band i shall wait. I was only going to see if it moved more than run, however i will be patient.

I have moved over to duckduckgo, i thought i would give it a quack. (Sorry crack)

[Tony]

I think that maybe a C ie 75403C

Is that a Mercedes symbol before the code?

[Heuer]

I should have been more comprehensive in my reply - DL3 75404 is the LHD motor, DL3 75403 is the RHD motor. Yours has a D mark so will have the thermal cut out. Even the early 4.2 cars (up to at least 1965) had the thermal cutout although with the E mark.

The Mercedes style symbol has nothing to do with the German car company. It is the Lucas symbol for 'part number'

[Tony]

Thank you David, As usual a very comprehensive reply. I hope when i get the parts i can stop asking so many questions.

I will update the forum on the outcome.

Tony

[Tony]

Yes, my wipers are working, Replaced the brushes,spring and tabs, bench tested it and it runs. Connected it to the car , plugged in all the wires and it ran fine. So I just need to connect it back into the car and connect up the linkage.
I read somewhere that for a right hand drive car the motor ( or more precise the spigot that connects to the wiper linkage) should run anti clockwise. Not sure from which way direction you look at the motor to check. Is it anti clockwise looking from the front of the car of from the back of the car.

Than again for the help.

Tony