Fuse for rear amplifier, non-Bose

[MooLard]

Hi there

I offered to have a look at my work buddy’s A6 with a standard stereo in as the rear speakers and sub is not putting out any sound. The stereo looks to work ok as there is sound out of the front speakers so I took a multimeter to the red connector that goes in to the sub in the boot. I can see 12volts on a white wire which I guess may be the switch to turn the amp on, but there is no 12v from the thick red and yellow wire. Oh it’s a standard non-Bose stereo, can anyone point me in the right direction for the fuse for this, assuming there is one?
Many thanks

 

[myth]

I can help you with a wiring diagram if you can tell me the year of the car, engine code and if the radio is chorus or concert.

 

[MooLard]

Evening! Thanks for the reply I wouldn't mind a look at that, I think it's actually a Symphony.

 

[myth]

I checked some models over the years and it seems to be used the same fuses:
F37 with 20A
F43 with 5A
F27 with 15A
F5 with 10A

 

[CHRISTOPHÉ]

I had this problem also on non bose with symphony head unit. It turns out it was the amplifier which is integral to the subwoofer housing, I bought a used one from eBay with some other bits worked out about £30 really.

Chris