Radio fuse stays hot when car is off?

[Foogoo]

I've been hardwiring A119s in mine and friends' cars piggybacking on either the radio or cigarette plug fuse with no problems. Trying to do the same on a 2000 Honda Accord however has me puzzled.

The Accord radio and cigarette plug share a 20A fuse. When the car is off, the radio and plug are off/cold as expected. The fuse however, remains hot, slowly going from 0v-12v over about a minute once the car is turned off.

The car did once have an alarm system which removed. I've pulled all the panels and checked every wire and plug for visible shorts or circuits that may have been left. I also disconnected the radio harness and the fuse still remains hot.

Any other suggestions of why the radio fuse remains hot (yet the radio doesn't turn on) when the car is off? Thanks.

 

[flip9]

Headunits need constant 12v to keep the RTC (clock) running and on older units to keep the radio stations and settings saved. The harness will have a constant 12v wire then an ACC wire to turn the headunit on/off.

 

[Foogoo]

Wow thanks, it's unfortunate to know I wasted so many hours looking for a non-existent problem.

 

[Foogoo]

Here's something weird, all the fuses remain powered, yet their devices are not operable. Could it be a relay from the old alarm?

 

[flip9]

The factory ACC/IGN relays are after the main fuses so yes its possible to find a lot of hot fuses as they are switched on/off down the line. The ACC fuse should definitely not be hot with the car off.

Below is a typical car wiring diagram. You will see many of the fuses are connected directly to the battery. The only fuses that wont be hot are the ones after the relays (particularly fuses after the AM1 and AM2 relay)

 

[Foogoo]

Thanks a ton for your help. Pulling up the specific wiring diagrams, they actually indicate which fuse is hot and when. I haven't gone through all the diagrams yet, but if all the ACC fuses are remain hot when off, my guess is my only choice is to tap directly into a wire after the relay?

 

[flip9]

Check the wiring diagram for your car and see if there's any cold fuses past a relay.

If there's none then you can splice into the cigarette sockets wire.