Ford Fiesta 2009. The passenger window does not go up or down. 

Pulled the door apart, unplugged the motor. Tested voltage on the motor connector with passenger switch on - 11.58V, same voltage as directly from the battery (it is not used much, need to charge, but driver's window works fine). Replaced the motor with a new one (tested, works 100%). Switch on - nothing happens. 

My mind refuses to understand: how can I have appropriate voltage and a valid device, but nothing happens?!

Is there any coding required for a new motor? Or is there some fault with the switch somehow? Is there any 'smart' electronics that measures voltage and somehow refuses to operate if certain conditions are not met? I did try popular advice about 10s up and 10s down (and vice versa) - does not help either.

It needs a full circuit.  As you've proven power, does it also have an earth?

If yes, then the wire is probably damaged, and not allowing enough amps through for the motor to operate, but fooling the meter with apparent battery voltage when no load demand.

Test for 12V with a test lamp - something that draws significant current.  A meter is a high impedance device, so does not draw any significant current.  For power you need both volts and amps.

12 hours ago, TomsFocus said:

It needs a full circuit.  As you've proven power, does it also have an earth?

If yes, then the wire is probably damaged, and not allowing enough amps through for the motor to operate, but fooling the meter with apparent battery voltage when no load demand.

Where should I look for this earth cable? There are only 2 wires at the motor, a lot more at the switch. What am I looking for?

9 hours ago, Paulkp said:

Test for 12V with a test lamp - something that draws significant current.  A meter is a high impedance device, so does not draw any significant current.  For power you need both volts and amps.

Do you mean a circuit tester with a croc clip and a light inside? I never used this method before with 12v, usually a meter was sufficient. But that was a boat's 12v.

When working on low voltage/high current circuits (ie a car) a voltmeter with it's very high input impedance (MegOhms) will not draw any noticeable current.  So even if there is a circuit resistance of 10-Ohms, then it will still read 12V.  However if you try and draw any current, you wicircuit.ll only get 1.2A.   Something like a headlamp bulb, as they will draw about 5A, but be careful with the glass getting hot !

So if you have 12V to the motor, you may still have a sufficiently high resistance in either the supply or chassis circuit to stop the new motor working.  Does a 2009 Fiesta have a door control module, or does it use good old fashioned copper wires, switches and relays ??!!

Analogy might be 8 AAAs in series, ie 12V, but it won't turn over a starter motor....

Never used a circuit tester, but I think they were for mains....

1 hour ago, Paulkp said:

When working on low voltage/high current circuits (ie a car) a voltmeter with it's very high input impedance (MegOhms) will not draw any noticeable current.  So even if there is a circuit resistance of 10-Ohms, then it will still read 12V.  However if you try and draw any current, you wicircuit.ll only get 1.2A.   Something like a headlamp bulb, as they will draw about 5A, but be careful with the glass getting hot !

So if you have 12V to the motor, you may still have a sufficiently high resistance in either the supply or chassis circuit to stop the new motor working.  Does a 2009 Fiesta have a door control module, or does it use good old fashioned copper wires, switches and relays ??!!

Analogy might be 8 AAAs in series, ie 12V, but it won't turn over a starter motor....

Never used a circuit tester, but I think they were for mains....

Thank you for the explanation of currents and resistance in cars! This is something a bit new to me.

I will find a spare headlight lamp and test again.

But how do I debug and find the problem if the light does not turn on? Particularly finding this mystical earth. Do I need to test every cable for resistance/continuity?

3 hours ago, Gedimin said:

Where should I look for this earth cable? There are only 2 wires at the motor, a lot more at the switch. What am I looking for?

There's no separate earth cable for window motors.  And in fact, that was poorly worded on my part.  It's technically negative rather than earth when in a car setting.

If you've tested across the two pins at the motor plug, then you have proven both positive and negative connections for a full circuit.  Most voltage testing we do is from one plug pin to a known good negative point, but that only proves the positive/power connection.

So if you do have the full circuit, but the motor isn't moving, then there isn't enough amps reaching it for some reason, usually due to a crushed or frayed wire, or a loose or corroded plug connection.  If that is the case, you do just have to go through methodically from the motor plug, through the door pillar plug and the BCM/fusebox plug etc.

55 minutes ago, TomsFocus said:

There's no separate earth cable for window motors.  And in fact, that was poorly worded on my part.  It's technically negative rather than earth when in a car setting.

If you've tested across the two pins at the motor plug, then you have proven both positive and negative connections for a full circuit.  Most voltage testing we do is from one plug pin to a known good negative point, but that only proves the positive/power connection.

So if you do have the full circuit, but the motor isn't moving, then there isn't enough amps reaching it for some reason, usually due to a crushed or frayed wire, or a loose or corroded plug connection.  If that is the case, you do just have to go through methodically from the motor plug, through the door pillar plug and the BCM/fusebox plug etc.

Ah, so there is no earth that I should be looking for? Some people (in other places) did suggest earth, but I could not figure what they meant - I only worked with simple 12v systems with pos and neg. 

Passenger window does not work both from its own control and from master control on the driver's side. Does it give any clue for the location of the problem?

With car connectors it seems very hard to trace a single wire - I would need to remove connectors or understand how to read every pin, right? At this point I'd rather install a mechanical window... 🙂

You probably have a broken control wire in either the passenger door harness or even the driver door harness, normally in the part that extends/flexes from the door to the body connector

38 minutes ago, Gedimin said:

Ah, so there is no earth that I should be looking for? Some people (in other places) did suggest earth, but I could not figure what they meant - I only worked with simple 12v systems with pos and neg. 

Passenger window does not work both from its own control and from master control on the driver's side. Does it give any clue for the location of the problem?

With car connectors it seems very hard to trace a single wire - I would need to remove connectors or understand how to read every pin, right? At this point I'd rather install a mechanical window... 🙂

It is difficult to trace car wiring, particularly for doors as more an more electronic tech gets added to those throughout the years.  Really you need a wiring diagram to follow from motor to source.  It needs to be specific to your exact year and model.

I seem to remember the power for these goes through the drivers door first, so a wiring break is not limited to just the passenger door.  As Dave says, damage usually occurs to the loom in the rubber boot between chassis and door where the wires bend every time the door is opened and closed.