Hiya. 

New to Skodas.

Recently had the car die on me. Battery light on, alternator not charging. Gave it a whack and charge voltage came back so I've replaced the alternator.

Few days later battery light comes on again. Seems to charge fine when not under load. Voltage drops when I put the fans, lights etc on and very slowly creeps down.

I've checked for breakages in the main positive wire from alternator to battery, all good.

Also checked the blue and red wires from alternator to ECU and bulkhead, also appear fine. 

Running out of ideas of what to check now, any help much appreciated 

Should add when you give it revs the voltage stays up at 14v. When idling under load battery reads from 13v down to 12.8v

Find and improve the bad connection you probably have. Disconnect main chassis to engine earth cable and clean both ends as a first step.

Usually goes from chassis leg to one of the two starter motor mounting bolts.

7 minutes ago, Breezy_Pete said:

Find and improve the bad connection you probably have. Disconnect main chassis to engine earth cable and clean both ends as a first step.

Usually goes from chassis leg to one of the two starter motor mounting bolts.

Will try that this morning. Was out investigating till late last night so may have missed something in the dark.

Ive already checked the earth from battery to chassis and from engine to chassis are there anymore I should be looking for?

Measure voltage drops between alt output stud and battery positive, with loads on. Then do same from alt body to battery negative. 

That should tell you which half of the wiring is responsible for the majority of the voltage drop.

 

How old is the battery?

9 hours ago, Breezy_Pete said:

Measure voltage drops between alt output stud and battery positive, with loads on. Then do same from alt body to battery negative. 

That should tell you which half of the wiring is responsible for the majority of the voltage drop.

 

How old is the battery?

Turns out it was one of the two little wires from alternator. I cut both of them close to the firewall and ran fresh wires back to the alternator, battery light off and seems to be giving correct readings.

Thanks for the help!