Punto Electric Window Fault

I need some suggestions as to what to look for on son's Grande Punto electric window.

Passenger side works fine. Driver side doesn't. It seems to have 10v at both terminals of the motor. The motor works fine in both directions. I replaced the switch thinking that this might be the issue but no joy. Relay next? Looking at the wiring diagram there only seems to be one relay for both windows - I'm not that familiar with modern stuff so is there a double-acting relay or am I reading the diag wrong? Any other suggestions. 10v seems to be an odd value on a 12v circuit - especially with no load.

A friends Clio 172 cup the cable snapped or wound round its self(i cant quite remember even though i fixed it)so there was power and some slight movement but it wouldn't go right up or down just a bit either side of where it was sat about 5 inches from top. An ebay replacement worked fine after a refit. The design was obviously to cut cost and very poor and i imagine a Punto might have something similar.

I would remove door card i think that is your best bet to investigate.

NB: While i looked on net for an electrical possible fault for his Clio before removing the card there was some sort of reset pushing both buttons for newer Clio's a work friend did this reset and it worked so maybe google Punto window faults first.

I've had the door card off a few times and googled faults. As above, the window moves fine with an external voltage applied so I'm pretty certain it's the supply.

Not 100% on the Grande, but presumably it has a large multiplug at the door/pillar joint. Have you checked and cleaned those connections?

Yes it does - I had a quick look and it seemed OK. I will be doing a much fuller investigation next week so I'm keen for ideas. I was particularly surprised to see voltage at both terminals of the motor connector.

When you say the motor works fine, you mean on the driver's side when you apply 12V direct to the terminals? And when the motor works the window goes up and down OK?

Do you measure 10V at both terminals when the motor is connected to the wiring loom? If you separate the connector, do you still see 10V at the connector?

Have you pulled out the relay, tested it, tried another?

Can you post up a wiring diagram? Is it a proper FIAT one or a Haynes type of best-guess diagram?

So - yes: motor works with an external voltage applied. The window goes up and down just fine.

The 10v is at both terminals of the free connector plug.

No - not yet tried a different relay partly because the only relay diag I've found so far only shows one relay and I was expecting there to be a relay per window.

I will try posting the Haynes version of the wiring diag (only one I have) when I'm back next week.

Does the diagram look like this? (from Haynes by the look of it)

It does in indeed show one relay supplying both windows via "dash panel switch assembly" which musty be Haynes-speak for a little central electronic module that controls various functions. For my wife's Volvo V40 I have just bought a second replacement CEM to sort out the headlights: there are mini-relays or connections inside the CEM that stop working, and whilst repair is possible, modern-day soldering (with lead-free solder and miniature components) is beyond my capability (tried it and generally failed). The solution may be a new "assembly" box (from a scrapyard).

That diagram is the first I found and is for a Punto rather than Grande Punto, although I suspect they are similar. Have you checked the Fiat Forum at all?

I think it's actually a better diag than the Haynes one. I've swapped the switch unit but that's made no difference. I'll take a closer look at that diag and see if it gives me some clues.

This PDF has the proper FIAT diagrams like the Coupe, again for a plain Punto, 2 pages for electric windows (17,18) and check last two pages for component names (no wiring colour code however, but they'll be the same as the Coupe I think). There is a window ECU (155) which looks to be just for the windows and nothing else, and perhaps interrupts the power to the switch when the door is open? But beware, this is for a Punto, not Grande Punto...I will keep looking...

Try testing the connections to the switch. If my memory of italian colours is correct, there should be a black cable (N) for earth, red (R) for power +12V when ignition is on (and perhaps when doors are not open?) and the other two should have nothing normally. When the switch is pushed to open, one should be +12V and the other earthed, and vice versa when the switch is pulled.

You may be able to swap the window switches on the driver's side (those for the driver and passenger windows) to test, but the connector shapes may be different.

Thanks, Dave. I need to take a more systematic approach to fault-finding this and I haven't had the time so far to dedicate to it properly.

The switch unit doesn't look as though I can swap stuff around and the connector is one big monoblock thing. It's possible that both the units I have contain the same fault but probably unlikely. I need to understand why there's only one rely too - that doesn't seem to make much sense to me as the windows operate independently. If there's also some other condition that needs to be met before the window will operate (like door closed) then maybe I'm hunting in the wrong place altogether.

I think that Punto diagram is old school, with a separate single ECU for the windows. I've found a Grande Punto workshop manual via the Fiat Forum here but it's in Italian

In section 9.4 "Alzacristalli elletricci" (page 474 of 534) it describes the electric window system, and it looks more similar to what I think you have. Is yours 2/3 door or 4/5 door? The 2/3 is understandably simpler than 4/5. However, you should still be able to test the signals coming out of the switch module when you try each window switch (still connected) by poking paper clips down in the holes where the wires enter the connector, and using your trusty voltmeter leads with croc clips) - but be careful not to short anything out...

Cool - thanks - I'm a dab hand at Italian car wiring diag.

The fault has clearly been investigated before because there are "pin" holes in many of the wires' insulation.

So with luck you will succeed where others have failed

I finally got to the bottom of this. The voltage I was seeing was indeed a floating earth compounded by an LED and resistor within the circuit supplying the downstream side of the switch. The earth issue was a right PITA to find. It turned out that the earth wire and been cut/bodged/altered within the rubber housing by the door multi plug. Once I found that, all became clear and he now has two working windows on his wagon.

Thanks for your help with the docs, Dave, though, frankly, they weren't any help. Quite what they think you are going to be able to do with them, I have no idea: especially with the blank boxes with five connections.

Glad you found it! Yes, man with voltmeter is a rare match for these new-fangled modern cars They make the Coupe seem so last-Century, oh wait, it is