VW T4 - alternator problems

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Posts: 266
Joined: Mon Mar 03, 2014 8:46 pm
Passat model: B5 1.9TDI Wagon
Location: Limousin, Central France

VW T4 - alternator problems

Post by alpenweiss2 »

Hello folks. I am asking in here as I have had no joy in the T4 forum (no replies) and I am also a member of the Passat forum.

In October 2020 the alternator failed on our 1998 T4 1.9tdi (professional conversion) which we have owned since 2011 and the conversion was done in 2012.

I suspected possible damage from a slight diesel fuel pump leak, dripping diesel onto the alternator.

Anyway I bought a new Stark Automotive (German made) alternator from Autodoc France online. 14 volts 90 amp one.

Fitted the alternator and all good for several months.

A couple of weeks ago the dreaded battery light stayed on. Took off the undertray and checked the alternator. Wiring looked okay but after checking the battery with a Voltmeter whilst the engine was idling, it was clear that the alternator was not charging.

Took it off and noticed that the blue exciter wire going to L on the alternator had a split in the plastic coating in the wiring loom, right next to the spade connector for the big battery cable connection to the alternator - maybe shorting out? I noticed with the ignition on that the aternator was making a slight sizzling noise??? Anyway repaired the wiring but noticed slight melting of plastic on the alternator body. Even with the wiring fixed it would still not work?

I was advised on another forum to buy a new regulator. I have done this and fitted it to the alternator at a cost of €28.50. As soon as I reconnected the battery I heard a popping noise. Dived under the van and the alternator is smoking without the ignition even being turned on!! Quickly disconnected the battery and it looks like I need yet another new alternator?

Any thoughts as to what would cause such catastrophic failure in such a short time? There are only three wires. A thick cable from the battery positive terminal; a thin blue wire to the L terminal on the alternator and a red/black wire to the W terminal. I just don't understand?

For the diesel leak I have it planned to drive the 150km round trip to Limoges to get it fixed. For now I have fashioned a temporary cover over the alternator to protect it from any drips.

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