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MK Indy with 6V at the washer pump
OrangeJuiced - 19/3/13 at 08:55 AM

I have the dreaded pre spring MOT booked and have a little elctrical issue.

The screen wash motor/pump is not working. Pointless as without a roof I never fancy a screenwash shower but VOSA think otherwise.

I checked every fuse - All fine.
I swapped the relays around with 1 I knew worked - All fine.
I checked the switch on the stalks - Fine. (stalks are off a MK4/MK5 Fiesta)
I checked the motor/pump with 12v - Fine.
Battery is over 12V and fully charged - All Fine.

I have checked the supply at the motor pump and have a constant 6.2V supply to 1 pin? I would have assumed (probably wrongly) that a poor connection would still give me 12V but not the current required to drive the motor/pump. Anyone able to explain the loss in voltage?

Cheers
Adrian

ReMan - 19/3/13 at 09:08 AM

How do you mean a "constant 6V supply"?
Is that before you press the wash button, suggesting a switch to earth?
Or when you press it, suggessting a resistive switch. so check the feed to the switch.

OrangeJuiced - 19/3/13 at 11:52 AM

It must switch to earth. The 6V is before I press the switch. I have just tried a cable straight from the battery to the positive side of the motor (bypassing the 6V) and pressed the button. Nothing happened, suggesting no earth or an incorrectly wired Stalk. I can probably unpick the loom to trace this issue but its really the 6V that is puzzling me. I can't fathom out where it is coming from or what can generate 6V?

ReMan - 19/3/13 at 12:24 PM

Is the 6V on both sides of the pump motor, before you press the button?

ReMan - 19/3/13 at 12:26 PM

Is the 6V on both sides of the pump motor, before you press the button?

snowy2 - 19/3/13 at 01:23 PM

Ohm‘s law.......put a resistor in a simple DC circuit and you will get a voltage drop. something is causing a resistance in the cct.

ReMan - 19/3/13 at 02:43 PM

quote:
Originally posted by snowy2
Ohm‘s law.......put a resistor in a simple DC circuit and you will get a voltage drop. something is causing a resistance in the cct.

Hence the Q ^^^^^^
I wonder if the motor is poorly

ReMan - 19/3/13 at 02:43 PM

quote:
Originally posted by snowy2
Ohm‘s law.......put a resistor in a simple DC circuit and you will get a voltage drop. something is causing a resistance in the cct.

Hence the Q ^^^^^^
I wonder if the motor is poorly

Westy1994 - 19/3/13 at 04:03 PM

quote:
Originally posted by OrangeJuiced

I checked the motor/pump with 12v - Fine.


If we assume this is true and it is a perm positive feed to the motor ( with the neg doing the switching) then you have some sort of high resistance in the positive supply somewhere, never had this myself before, any chance of doing a temp test as close to the switch as possible? Using a single cable direct from the switched side of the switch to the motor ... Seems you have checked everything else ...

OrangeJuiced - 19/3/13 at 09:24 PM

Thanks for all the discussion.
I think I have 2 separate issues. Lack of 12v at the motor and a bad connection somewhere after the stalk switch. I had to stop tracing the fault to fix another of my making as I had dislodged a fog light connector! Damn Electrickery!
According to VOSA I need to provide provision to clean the screen. I'm thinking a temporary switch that simply turns on the pump will have to do for Friday.
Thanks again.

scudderfish - 19/3/13 at 09:27 PM

Or take the screen off (if you can)

OrangeJuiced - 28/3/13 at 09:37 AM

It passed!
Had to rig a temp switch but i now have the time to fix her properly ready for the s*mmer! Ssshhhh! Dont want to say it out loud incase i scare it away!
Thanks for your help.