Hello everyone, I'm sorry my English is bad but I think I have a problem with the alternator.
  I have EPC, ASR lights, so I tested the alternator with a multimeter and it shows 13.80V, and on the VCDS measuring block 53 in module 01 it shows 13.20V.
Why is there a difference and where should you first look for the problem, the voltage regulator of the DMF wire or...

Welcome to the site

 

I would check the alternator wires down at the gearbox. Does the battery light come on with the ignition turned on (engine not started)?

Edited 22 January, 20233 yr by TMB

Thanks TMB
The battery light comes on when the ignition is on and goes out when the engine starts, the weather here is very bad right now, so I can't even check the wires under the car, I have to wait for better weather.
I am more interested in why the VCDS shows one value and the multimeter shows another and there is a big difference

30 minutes ago, Zehrudin said:

Thanks TMB
The battery light comes on when the ignition is on and goes out when the engine starts, the weather here is very bad right now, so I can't even check the wires under the car, I have to wait for better weather.
I am more interested in why the VCDS shows one value and the multimeter shows another and there is a big difference

 

VCDS is not a calibrated measuring instrument, neither is the ECU, also half a volt is not a big difference. If the wiring's good then your alternator voltage regulator is toast.

Thanks sepulchrave

I will try to replace the regulator and hope that will solve the problem.

On 22/01/2023 at 16:56, Zehrudin said:

Hello everyone, I'm sorry my English is bad but I think I have a problem with the alternator.
  I have EPC, ASR lights, so I tested the alternator with a multimeter and it shows 13.80V, and on the VCDS measuring block 53 in module 01 it shows 13.20V.
Why is there a difference and where should you first look for the problem, the voltage regulator of the DMF wire or...

What does the last measuring block value in 53 read, after the voltage?

May be labelled "Generator load".

Edited 23 January, 20233 yr by Breezy_Pete

Pozdrav Breezy Pete

it reads there 0,0%

I think that confirms the breakage of the DFM wire between alternator and engine ECU.

Edited 23 January, 20233 yr by Breezy_Pete
Typo

You may also need to clean up the connections of the high current connections in the charging circuit. The earth wire from chassis leg to mounting bolt of starter motor (the main engine earth) would be my first suggestion for improving alternator voltage numbers.

 

 

Thanks, I'll check the DMF wire and ground until the snow and rain are gone.