Electrical - Aux battery and Fuse 3 - No lights and no cig

[VicVan]

Just installed an auxiliary battery. Yandina combiner, Blue Seas fuse box, the whole 9 yards. Works fine, EXCEPT one thing... I can't have the radio/lights/cig lighter run on the aux battery.

Vehicle: 1990 Westfalia full camper. had the relay under the driver's seat.

What I did: install the aux battery. I used the existing red wire that runs from the driver's seat battery box to the fuse box, removed it from panel P (permanent +12V) and plugged it in lower socket of fuse 3, so I could have radio/lights/cig run on the aux battery.

What happened: The lights and cig lighter stopped working, the radio still worked.

I removed the spade. Turns out:
1/ There is +12V at the lower spade of fuse 3 socket, contact on or off;
2/ The radio works no matter what, i.e. it is not on fuse 3.

Questions:
1/ How is my radio powered? Are we looking at a possible case of PO's bamboozle?
2/ If my radio is not on fuse 3, why do I have +12V at the lower socket of fuse 3, and why won't the lights work?


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'90 Little Blue Truck, 2WD auto, FAS GenV 2.0 NA (AVH)

[crazyvwvanman]

There are 2 versions of the 86-91 fuse panel. The 2 pins for fuse #3 are reversed in the later version.

With nothing in the 2 pins of fuse slot #3, measure the volts on each pin compared to ground. 1 pin should have constant +12 from the main battery.
DON'T use that pin. Plug the aux battery wire spade into the OTHER pin. That should move what was using fuse #3 to now use the aux battery power. Make sure the wire from the aux battery has a fuse near the aux battery end.

As for why the radio works with nothing in fuse slot #3, sounds like a previous modification.

Mark

[VicVan]

Lux fiat! It works. Thanks Mark.

Regarding the inversion of the fuse for the later models, is it something I could have found out on the Bentley?

I put a 15 A fuse.

As for the radio, I'll have to do some exploration...
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'90 Little Blue Truck, 2WD auto, FAS GenV 2.0 NA (AVH)