windscreen wiper moter RRC

jan_rrc39v8 · Post by **jan_rrc39v8** » Fri Jun 01, 2012 8:37 pm

can a wiper motor function at half power? My wiper moter can only wipe the blades over dry glass very slowly to the point of nearly stopping halfway.

i took the moter out and it ran nicely without the mechanism attached.
i opened up the gearcase and there was enough grease in there. No damage to the gears.
i undid the motor slightly to try to get a good look at the brushes, i counted 3 (correct? and they are all of sufficient lenght)
i couldn't find anything wrong so i reinstalled it making sure to reattach the small mass wire

i also used liberal squirts of ATF to lubricate all swivelpoints in the mechanism.

then i tried the wipers again.
result: disappointing, hardly any change...

fyi: the starter motor turns fast and powerful. so battery OK.
other users do not dim( engine off) when i also switch the wipers on.
no blown fuses.

What's the verdict on this wipermotor? is it on it's last legs?

JSF55 · Post by **JSF55** » Fri Jun 01, 2012 9:00 pm

Have you checked all the connections and motor earth first ?

jan_rrc39v8 · Post by **jan_rrc39v8** » Fri Jun 01, 2012 9:30 pm

there is a little mass/earth strap that connects the wipermotor casing to the carbody. i cleaned both ends and re-attached them tightly.

am i overlooking something?

JSF55 · Post by **JSF55** » Fri Jun 01, 2012 9:44 pm

I would check the fuse connections, switch connections and motor connections too

DaveEFI · Post by **DaveEFI** » Fri Jun 01, 2012 10:40 pm

jan_rrc39v8 wrote:there is a little mass/earth strap that connects the wipermotor casing to the carbody. i cleaned both ends and re-attached them tightly.

am i overlooking something?

On my SDI, that earth strap is just to ground the assembly - probably to prevent it radiating interference as it is insulated from the body. The motor ground is in the harness. The body of the motor is not connected to ground.

My theory is these older Lucas motors loose their efficiency due to the magnets becoming weak with age. I bought a NOS one from Rimmer which was no better. And I did check for voltage drop from the actual battery.

My cure was to fit a modern ferrite magnet motor from a BMW, made by Valeo. Bench tests showed it produced 2.5 times the torque at stall than the Lucas one, for approx the same current. All down to the much better magnets.

However, before going to those lengths, clean all the connectors, wiper switch, and the relay contacts in the delay unit.

ChrisJC · Post by **ChrisJC** » Sat Jun 02, 2012 9:00 am

Check the voltage at the motor when it's running. Obviously it should be about 12V or more. If it's e.g. 5V, then you've got bad wiring somewhere.....

Chris.

jan_rrc39v8 · Post by **jan_rrc39v8** » Sat Jun 02, 2012 10:08 am

thanks for all the pointers , i will check those first.
@DaveEFi: I would be interested to know which BMW model/year could be a donor.

DaveEFI · Post by **DaveEFI** » Sat Jun 02, 2012 11:29 am

I used an E39 one, since I have a 528. The wiper motors don't seem to give problems, so are cheap and plentiful secondhand. It looked to be about the same physical size and shape. But it could well be there are others even more suitable.
The only difficult part was adapting the drive lever fitted to the Lucas motor to fit the Valeo. The Valeo uses a splined and tapered drive rather like the wiper arm ones. I made up a taper bush by bolting a number of washers together - all with different size holes to achieve the taper. Then welded them to the arm.

Of course you might well think of an easier way depending on what facilities you have.

New mounting holes on the frame have to be drilled for the motor. You also have to add a relay for the parking switch as the Valeo uses a micro switch for this rather than the Lucas high current one.

I did an article for the SD1 club mag giving full details - it's in Issue 108 which I think you can view online.

ChrisJC · Post by **ChrisJC** » Sun Jun 03, 2012 9:28 am

jan_rrc39v8 wrote:thanks for all the pointers , i will check those first.
@DaveEFi: I would be interested to know which BMW model/year could be a donor.

It shouldn't be necessary. The Range Rover wiper motor is perfectly OK when everything is working OK.

Chris.

DaveEFI · Post by **DaveEFI** » Sun Jun 03, 2012 10:56 am

ChrisJC wrote:
jan_rrc39v8 wrote:thanks for all the pointers , i will check those first.
@DaveEFi: I would be interested to know which BMW model/year could be a donor.
It shouldn't be necessary. The Range Rover wiper motor is perfectly OK when everything is working OK.

Chris.

The SDI one was too - when new. I tried totally bypassing the original wiring etc and running it straight off the battery. It still stalled on a near dry screen on normal speed. The Valeo doesn't.

Many SDI owners 'cure' it by fitting shorter wiper blades.

BTW, I'm assuming RR of the same age used the same sort of system.