Hey

 

My ASR light comes on after exatly 10min and no battery light when ignition is on.

 

Battery light might come on and blink occasionally when the car is running but seems like the rear defroster triggers the light when pressed as the rear defroster won't stay on.

 

It's a 2006 1.4TDI Fabia with the 55kw AMF engine

 

I know this seems to be a common issue with Fabias and other VAGs as well.

 

I'm running out of ideas how to sort mine out as the usual suspect is the load signal wire being chafed or cut

 

So far I've tried the following

New MAF (Was suggested somewhere so decided to renew at only £25)

New (used) Alternator + new voltage regulator (Charging at 14.3 at idle and under load)

New exciter wire (blue) directly from Alternator 2pin to the main connector under windshield wiper cowl (flux, solder and heatshrink))

Bypassed the 2pin - electrical connector at gearbox for the DFM/load sense wire to ECU and measured with a multimeter for 0.06Ω resistance when measured directly from 2pin connector at alternator (flux, solder and heatshrink)

Both lines from the 2pin connector on alternator show ~11.4v with ignition on.

Decided to change the battery yesterday for a known good one I had laying around

 

It seems like my only remaining option might be the ECU - please convince me it's not 😁

 

It's not.

 

Clearly the broken wire only loses continuity when the engine's running so simply replace the other wires as well.

2 minutes ago, sepulchrave said:

It's not.

 

Clearly the broken wire only loses continuity when the engine's running so simply replace the other wires as well.

 

Sorry, what other wires are you referring to?

39 minutes ago, Jiba said:

 

Sorry, what other wires are you referring to?

 

There are two running from the alternator, you mention replacing one of them, you say you've bypassed the plug under the gearbox but you really need to run a brand new pair of wires all the way from the alternator to the ECU to be certain.

@Jiba - I was thinking pretty much the exact same thing as @sepulchrave , also known as a "hot short circuit". If you've replaced one of the control wires, the issue is clearly with the other one.

26 minutes ago, KenONeill said:

@Jiba - I was thinking pretty much the exact same thing as @sepulchrave , also known as a "hot short circuit". If you've replaced one of the control wires, the issue is clearly with the other one.

I'm going to replace the wire going from Alternator to the ECU today fully - thanks guys!

 

I'm a bit dumbfounded as the blue exciter wire should control the battery light which has been replaced but the light still doesn't work as intended
 

The DFM/load sense wire "hot short circuit" might be the case for the ESR light - I'll get that checked out

2 minutes ago, Jiba said:

should control the battery light

Yeah, but you don't actually care about the 'battery light' as such; what you care about is that the alternator is turned on when required.

Blue wire fault might be within cabin?

Goes to the onboard supply control unit.

 

58 minutes ago, Wino said:

Blue wire fault might be within cabin?

Goes to the onboard supply control unit.

 

I've checked with a multimeter that the connection from the main harness pins to the onboard supply control unit should be fine and dandy, Although the problem might be within the plug itself but should present itself with a myriad of other problems if the plug is faulty 😀

It would be nice to have an oscilloscope on the DFM wire; don't suppose you have access to one?

On 12/03/2020 at 16:11, Wino said:

It would be nice to have an oscilloscope on the DFM wire; don't suppose you have access to one?

 

Sorry mate, that's something I don't have :S

 

 

Went on an replaced the line to ECU with no difference, so both lines are new now within engine bay and under cowl

You might be able to see the DFM waveform as a variable voltage; depending on how your meter samples it. For a given engine rpm the 'effective average' voltage of the PWM signal from the alternator will decrease as more electrical loads are applied to the system, I think. Might be the other way round, can't remember just now.

Measure while both ends are connected, probing into the back of one of the connectors' cable entry.

Edited 13 March, 20206 yr by Wino