Wiper motor connection

Gentlemen,
Today I had cause to investigate a wiper motor electrical fault someone reported on a 2009 Beemer 7 series. Upon disconnecting the power feed to
the motor, inspecting the plug wiring showed 3 wires in total. Two of these appeared good for probably 10A or so, the third, thinner wire perhaps 1A tops. The wipers are normally functioning in three options: fast, slow and intermittent. Since the motor was not in an easy location to view fully, I am unable to determine if its case was earthed or not. What is the most commonly encountered scheme for powering up motors with 3 wires, please? I mean, I know how *I* would go about it, but the Bosch, for some reason, have done it differently and I can't work out how without removing it entirely and stripping it. Can some kind soul save me the bother?
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If it is like the Valeo wiper motor on my last BMW, the thin wire will be the feed from an internal micro limit switch. With a relay (or whatever) external to the motor to switch the full motor current when parking, etc. Unlike the Lucas system you're probably more familiar with where the limit switch carries the full current.
But that motor had four terminals, one being ground. Other two fast and slow. Intermittent was basically a timer which pulsed the slow speed - in other words, started the motor and let the parking circuit stop it. Then repeat.
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On Sat, 12 May 2018 00:23:40 +0100, Dave Plowman (News) wrote:

Ta Dave. I'll take a butchers in the light of that tomorrow. I also like to take resistance measurements from the connectors once the motor is out of situ as it eliminates the possibility of some black magic going on at the side that can't be seen all the time it remains mounted.
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It's possible modern motors contain electronics. On all the ones I've played with they were external.
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On Sat, 12 May 2018 17:37:26 +0100, Dave Plowman (News) wrote:

Looks like that's it. None of the static resistance measurements make any sense otherwise. The lowest resistance I'm seeing with *any* combination of the wires-to-wires or wires-to-ground is 56k which rises over time to over 70k before I lose the will to live. So clearly some capacitance there for some reason. Even at 56k the current would be too small by miles to be able to operate a wiper motor so there's some monkey business going on here which requires complete excision and investigative strip- down. Thank god I don't have to deal with this crap for a living!
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Thinking about it, I made those measurements with a digital meter which uses *very* low probing voltages and has *very* high input resistance. Maybe I should get the old Avo out and check those same resistances at 1.5V and 20 kohms per Volt instead. Maybe there are diodes inline that are not being turned on at the DVM test voltage...
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It's odd it appears to have the old three brush system for hi/lo speeds. With electronics, would make more sense to control the speed using PWM.
I suppose the motor is known to be good? Have you Googled for details of that exact motor? It won't be made by BMW. My E39 had a Valeo unit.
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On 12/05/2018 17:37, Dave Plowman (News) wrote:

The modern cars are using two motors and no linkage must be servos/steppers or they'd go out of step with each other ;)
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Ah - not come across one like that. Makes some sense, though, once you go down the electronics route.
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Dave Plowman (News) used his keyboard to write :

The fourth one must have been a permanent (ignition) live, to allow it to have power to park.
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Not so. The limit switch provided a ground which operated an external relay (part of the delay unit). So no need for a permanent live to the motor.
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On 14/05/2018 00:04, Dave Plowman (News) wrote:

that was not the case on older systems.
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Yes - said that earlier. As I've fitted a more recent wiper motor to my SD1.
The original - Lucas - was the same when either used stand alone or with a delay unit. If you are making one for delay only, no need for the high current switching inside the motor. Easier to do it all in the delay unit, using a low current signal from a micro switch to give the park position.
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wrote:

Same era BMW/Mini wiper module operation taken from the wiring diagram system CD
Front wiper motor The wiper motor is a rotary motor without electronic modules. The wiper motor is configured for two different wiper speeds. The wiper motor is activated via two external relays. The wiper motor's end position (off position) is detected by a reset contact integrated in the wiper motor. The reset contact switches earth to the JBE as soon as the wiper motor has reached the end position (rest position). The reset contact is also used for monitoring the wiper motor.
Diagram here - wiper motor (3) and relay (2) at top left
https://ibb.co/bMJkWJ
Note that switching contact mentioned above is shown as not connected on this simplified diagram
The reset contact also signals correct wper operation to the JBE such that after 16 seconds after switch on if a reset has not been received the JBE no longer operate the relays and thus the motor for protection against wiper blade freeze to the screen or a mechanical wiper arm block
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On Mon, 14 May 2018 09:09:11 +0100, The Other Mike wrote:

many thanks for that, Mike.
I'm going to have to come back and view this diagram again in a day or two when time and physical health permits. Right now I can't even work out what a "JBE" is.
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wrote:

Junction Box Electronics. It's the thing that sits at the heart of the car interfacing with almost everything else. Often under the dash or behind the glovebox or in the footwell just forward of the door
Commonly has lots of relays and fuses on one side of it (and a few relays in it) but also a shedload of electronics and interfaces to the Body CAN bus and the Engine CAN bus plus the interface for the diagnostics
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