Voltage problem? What does VAG-COM measure?

[pargyrak]

Hi all,
I am experiencing problems with my 1.8 16V Seat Ibiza ADL engine.
037-906-024AR is the ECU number.

From time to time it works perfectly and from time to time it stalls and behaves like a bunny

I borrowed a friends VAG-COM (and laptop) and I drove around measuring block 2, where I could see, while the engine was working well, the voltage being almost steady around 13.87.

After a while though the engine started misbehaving again and the voltage was extremely erratic from 6V to 17V. I guess this is not normal right?

I stopped on the side and I measured the voltage on the battery. It was steady at 14.22, while the VAG-COM was still showing erratic behavour voltage wise.

I guess VAG-COM is measuring the voltage fed to the ECU right?

What could be the problem ? Alternator? Grounding? More ideas?


Thanks!


pargy


PS The engine is installed on 1997 Toledo formerly 1.6lt 101hp

[cheshire cat]

power relay?

[pargyrak]

power relay?


I went today to the shop and they did a test run with their 1552 after the grounded the alternator.

The bloody thing worked for 5 mins properly till I left the shop and then the problem occured again. They even said the maybe the laptop did not show correct results.

I drove back again took their 1552 by force and showed them the voltage was going like crazy and not me.

Unfortunately the electrician was not there today to fix the problem but they said either a relay has "frozen" (expression translated from Greek) or some wiring problem.

Thanks!

pargy