No Battery warning Light, Alternator not charging unless Revved

[booke23]

Hi all,

Just got myself a 2006 Fabia Estate 1.9 TDI.

I've got no battery light when I turn on the ignition, and when I start the car the alternator does not charge unless I rev the engine to about 2000 rpm, where upon it continues charging whatever the RPM until I shut it down.

I've read about the issue of broken wiring in front of the gearbox, and was thinking this was the problem. But I took the multi-plug off the alternator and with the ignition switched on measured 8.2V on the L wire (blue wire) and 11.7V at the DFM (grey/red[orange?] wire).

This would suggest that there is not a complete break in any of these wires, however 8.2v sounds low on the L wire......does anyone know what the normal voltage should be?

I should mention that when I scanned with VCDS there was a 01117 fault code - Generator Terminal DF Load Signal 27-00 - Implausible Signal......ross tech wiki suggests this could be either a wiring issue or alternator/voltage regulator issue.

Any views welcome!

Edited 30 August, 2012 by booke23

[hockeylad72]

Would think it is the load signal wire that has a break in it.

Have a look here http://www.seatcupra.net/forums/showthread.php?t=209472

It's below the starter, one does the alternator and the other supplies the a/c compressor.

I have had both break on me, I would suggest doing both.

Cheers

Davie

[Tech1e]

So you have read about the broken wire in front of the gearbox? Read the thread on it and looked at the pictures etc etc

and still not checked the plug?

[booke23]

Thanks hockeylad. That certainly seems to be the main cause of this issue.

But I'm confused as to why I'm able to measure voltage at both wires at the alternator end. I want to rule out regulator/alternator issues before doing a bypass on the gearbox multiplug, although even if this isn't the cause it sounds like it could be good preventative maintenance.

So you have read about the broken wire in front of the gearbox? Read the thread on it and looked at the pictures etc etc

and still not checked the plug?

Thanks for that tech1e.....that helps alot.

[AndyPandy]

Reading voltages in various places,in a bit misleading.The reading depends on the impedance of the meter.Meters are best used to measure voltages ,at a point where load is being taken.To make my point a reading at the battery may be 12.7 volts ,(engine not running) .The same meter on the same range would read 12.7 volts at the cigarette socket (nothing plugged in). The same meter reading across a rear light bulb (switched on) would be say 12.4 volts ,The drop is due to the resistance of the wire ,fuses,and switches. So a low reading of say 11 volts again across the bulb ,would indicate a bad switch,or connection.

Regarding the Seat Cupra repair, you should always use the same colour wires as the original, when you extend or replace bad wires,it makes it a lot easier for the next person (or even you in a few years ) who is tasked with the job of faultfinding!!

Edited 2 September, 2012 by AndyPandy

[booke23]

Yes I think you're right Andy. I jacked the car up yesterday, got the undertray off and had a look at the offending plug.

Sure enough there was damage to both the blue wire and the brown/orange wire. But they had chaffed against part of the black outer sheath that protects the wires......just before the plug.....the multi-plug was fine.

The chaffing had exposed the copper wire which had corroded and was in bad state. I think maybe one strand of copper was still intact, hence the (low) voltage I was able to measure. No doubt this single strand had so much electrical resistance, that it might as well have been cut.......hence the fault code etc.

I did a bypass on the plug, to stop that causing trouble in future and it's all working again.

Thanks for your thoughts!

Edited 2 September, 2012 by booke23