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Discussion Starter · #1 · (Edited)
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Apologies in advance if too much detail, but rather that than too little.

Head unit packed up in SWMBO's Corsa C. Took the opportunity to replace with one that has the bluetooth, etc, that she wanted: Sony MEX-BT3100U

When I installed it, it wouldn't work; I tried the old trick of swapping the yellow and reds around and all seemed OK -- until the ignition key is removed, when it loses all memory.

I also have a SONY (older, etc) in my car, so I tried to isolate the fault by swapping them round. Both work fine in my car; neither works properly in hers, so I resorted to a voltmeter. This is where things got weird!

With the ignition off and radio disconnected, the permanent supply (yellow) and switched supply are both 12.xV
When I connect the radio, the yellow pd drops to around 8V.
When I connect the radio and switch on the ignition, the yellow pd drops to around 2.5V

The red pd appears to behave as it should (drops to a tad under 12V until engine is running).

I assume this behaviour on the permanent supply is not normal, so:

Is it a known "feature" and, if so, how do I rectify it?
If it's not easily fixable, is there somewhere else I can run a permanent supply from easily?
If I run a permanent supply from elsewhere, shuld I fuse it, and with what value fuse?
Is there another obvious-to-everyone-else question I should have asked (& if so what is it and its answer?)?

I know next to nothing about auto-electrics, so imbecile-proof responses will be welcome!

149 Posts
This is a known feature with the facelift corsa C's with CANBUS, you need either an ISO to CANBUS adaptor (I use this one)

You can also swap the live one for the cigar lighter.

You can run memory to both, the radio is fused so you don't have to, but the radio will need manually switching off when leaving the car
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