Washer Motor Wiring

[JerrySab]

This is more of a vent.
Was experiencing some electrical gremlins with the windshield wipers. Intermittent function didn't work. Wipers don't park at bottom. Wash was working but then it started acting fussy. The wand on steering column had quite a bit of play, so found a new one. Then began testing continuity in wires. Was tracing the ground wire attached to the washer motor plug.

ok. Despite radiator ground being 6 inches away from the plug. this ground wire travels all the way back to firewall, u turns, then tucks into a connector, which then runs DOWN THE FRAME AND DISAPPEARS BEHIND THE INLINE PUMP SHIELDING AND GROUNDS GOD KNOWS WHERE I haven't found the connection point yet WHY

 

[Curious Hound]

This is more of a vent.
Was experiencing some electrical gremlins with the windshield wipers. Intermittent function didn't work. Wipers don't park at bottom. Wash was working but then it started acting fussy. The wand on steering column had quite a bit of play, so found a new one. Then began testing continuity in wires. Was tracing the ground wire attached to the washer motor plug.

ok. Despite radiator ground being 6 inches away from the plug. this ground wire travels all the way back to firewall, u turns, then tucks into a connector, which then runs DOWN THE FRAME AND DISAPPEARS BEHIND THE INLINE PUMP SHIELDING AND GROUNDS GOD KNOWS WHERE I haven't found the connection point yet WHY

Why?

Because you haven’t ordered the EVTM or wiring diagrams book for your truck that would tell you where to find that ground connection.

It doesn’t make a lot of sense to us. But some things like that are done solely for the purpose of making the manufacturing process easier. If you had been there to see how the wiring harness was installed in the factory and where that falls in the overall assembly process for the truck, there’s a good chance it would make more sense.

When we do things to repair or modify our trucks, we often only deal with a few wires and components. We look for the closest and easiest place to mount and connect things. We think about it as “how can I route these one or two wires from here to there around all the crap that’s in the way. But the truck wasn’t Built that way. Here, at BMW, the body wiring harnesses are some of the very first things installed in the empty body. Some wiring harnesses under the hood are installed early. But the drive train is installed with most of itself wiring on it and then the loose ends are connected to. The car once the drive train is in. It’s crazy. And if you look at the finished car, you would wonder how did that get from here to there and why is it done that way?

 

[RonD]

The washer and wipers shouldn't share the same ground in most years

A long ground wire for Cab operated electrics in engine bay may be to bond a circuit together, as all "grounds" in a vehicle are not always the same
Engine and trans sit on rubber mounts so no connection to frame or body
Body sits on rubber mounts so no connection to frame

Usually the Battery's main ground cable attaches to the engine, for starter motor and alternator use, the 2 largest AMP circuits

There can then be 1 or 2 smaller battery ground wires to Rad support(headlights/horn) and inner fender(relay grounds)

There is always a ground strap from the rear of engine's head to Firewall, this is the main ground for ALL cab electrics, drivers side head on a V6
Its often left off after engine work, so check for it

Then a ground strap on bottom of the cab to frame(tail lights and fuel pump)
Also, if a pick up truck, a ground strap from frame to under side of bed

When in doubt ADD A GROUND
Engine to frame
Engine to Cab
Make sure rad support and inner fenders have good grounds



Wiper Park is a 12volt thing not a ground or wipers wouldn't work at all
In the wiper motor transmission is a wheel with a Peg on it
The wheel will rotate 360deg with one wiper cycle, park to park
The Peg will contact a micro switch that will be push open and that cuts key on wiper power
When wiper switch is ON, low or high, the turn signal switch provides 12volt power all the time, and the micro switch has 12volt power as well from the same fuse but directly, not from/thru turn signal stalk

When you turn off wiper's 12v from the turn signal stalk or interval wiper power is turned off, then micro switch still provides 12v until the peg opens the micro switch which happens when wipers are down all the way, so "they Park"

If you shut off the wipers and they just stop where they are then Park micro switch has no 12v to keep the wipers working or micro switch is bad

Same if interval wipers only come on briefly and stop, the interval wiper circuit just gives the wiper motor a brief 12volts to move the wheel with the peg so the micro switch closes and takes over powering the wiper motor until the peg comes back around and cuts 12v, in Park position
So the "delay" interval is just timer circuit which gives the wiper motor a brief 12volt shot, to start it thru one cycle

 

[JerrySab]

@RonD thank you so much for this. So thorough. Stoked to (hopefully, finally) put some of these issues to bed.