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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 04-01-2016, 02:51 AM   #1
hatetolovee46
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windshield washer pump signals

One of the last things to do on my latest e46 is windshield washer pump. I was just going to get a new one shipped but happened to have a dmm under hood already so added gator clips and 22 guage wire and tested the harness, 2 pins one is a good ground, other pin is seeing a steady 8.95v to ground with car off?
This normal struck me as odd?

Someone go check if you have dmm/gatorclips/22guage stiff wire(needed setup for most harness testing) and are bored thanks, otherwise will just replace it and see is cheap.

Lol at dealers wanting 120-180 for this(from quick prepost searches)

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Old 04-01-2016, 09:57 AM   #2
Cobalt23
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I haven't put a meter on it. But got a replacement pump for about $10 online and replaced it in about 15 minutes. Low effort/$ high reward.
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Old 04-01-2016, 10:00 AM   #3
hatetolovee46
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Yea i know its 15min job just found it odd its fed a constant 9v
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Old 04-01-2016, 02:09 PM   #4
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One wire is ground and the other is about 9V. Nothing unusual about this, because the 9v wire is the input into the DME for reading the signal from the level sensor. The 9V is a "soft pulled up" by connected to 9V via a 5K ohms resistor, typically. This means when the level is full the reed s/w shorts out this soft 9V to GND and the signal = 0V (not empty), or reed opened with signal = 9V (empty or disconnected).

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Old 04-01-2016, 02:21 PM   #5
hatetolovee46
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Interesting 9v inputs to dme i was not aware of woulf explain it, i am talking about washer pump however but presume same
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Old 04-01-2016, 04:02 PM   #6
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Ooops!! my bad. For this little pump the DME probably has one wire to 9v (internal regulated supply form batt) and the other wire is switched to GND for pump ON and opened for pump off. Are you sure one of the wire is grounded constantly? If one wire is permanently grounded, then the 9v you see is just a floating voltage with very little current from the motor driver FET transistor, which is normal to see floating voltage without any load (pump) connected.

2 cases: either a hard 9V and floating ground (to be closed by FET switch commanded by DME), or hard gnd and floating 9V via FET transistor and this floating 9V will be PWM or switch to hard 9V by the FET under DME command.
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Old 04-01-2016, 04:38 PM   #7
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Probably, you washer pump motor is "open." (bad brushes or corroded windings) The 9V would just be there because of a very small (and normal) leakage current. If the motor were good, you would see something really close to zero volts instead. It should switch to around 12V when you press the wash button.

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Old 04-01-2016, 05:21 PM   #8
skylane5sp
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Because of the high input impedance of a DMM, it is not uncommon to "see" an open circuit voltage that wouldn't show with the normal load or with an "old school" VOM.
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Old 04-01-2016, 06:15 PM   #9
hatetolovee46
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What joe? Pump was unplugged was harness that saw 9v to ground on one pin .2ohms to ground on other(and 0v obv)

What sky? What open circuit am i seeing? O.o

Sapote i get what you are saying, ground is held by (ecu?) And switched off when it sees closed circuit and washer pump command not sent to stop pump? Dont get why control it that way though

Or 9v is held because it doesnt detect closed circuit? And if it did(plugging pump back it) would release the 9v untill spray command given?

Still seems over complicated why not just 0v off 12v when you pull lever? :shrug:

What are fet transistors sapote
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Old 04-01-2016, 06:16 PM   #10
hatetolovee46
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Could it be the pump is held at 9v and only closes an internal circuit when 12v is fed? Still wouldnt get why do it that way
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Old 04-01-2016, 07:35 PM   #11
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Buy this

http://amzn.com/B0066TLNT6

Put it in, be done with it.
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Old 04-01-2016, 09:24 PM   #12
Sapote
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Quote:
Originally Posted by hatetolovee46 View Post
What joe? Pump was unplugged was harness that saw 9v to ground on one pin .2ohms to ground on other(and 0v obv)

What sky? What open circuit am i seeing? O.o

Sapote i get what you are saying, ground is held by (ecu?) And switched off when it sees closed circuit and washer pump command not sent to stop pump? Dont get why control it that way though

Or 9v is held because it doesnt detect closed circuit? And if it did(plugging pump back it) would release the 9v untill spray command given?

Still seems over complicated why not just 0v off 12v when you pull lever? :shrug:

What are fet transistors sapote
0.2 ohm means one wire is connected to GND. This means the other wire is driven by a FET (a 3-pin transistor with Gate pin connected to command signal from DME, Drain pin to 12V or 9V, and Source to the pump). When FET is off (pump off) the Source has some leakage from Drain (12v or 9V) and so the meter might read 9V, but when connected to the pump then this leakage voltage will be pulled down to 0V by the pump motor. The FET is like a switch controlling by DME to close or open instead of a human.
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Old 04-01-2016, 09:26 PM   #13
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So nothing is complicated about this -- just a FET switch ON or off to run the pump.
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Old 04-04-2016, 02:57 PM   #14
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Quote:
Originally Posted by Sapote View Post
So nothing is complicated about this -- just a FET switch ON or off to run the pump.
Exactly...
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