924Board.org

[mgatlag]

Just installed a new switch today and want to wire the radio as it is supposed to be. Put key in, and radio comes on. I found the pin on the rear of the new switch that gets power when I put the key in and it's the little red wire. Followed it back to the fuse box and lost the wire when I got close to the back of the fuse panel. Couldn't see where it ended and didn't want to cut the zip ties that keeps everything nice and together.

What I'd like to know is...can I run a wire from the (switched) power line off the radio and tie into the wire that comes out of the back of the ignition switch that gets hot when I put the key in? I'd obviously put an inline fuse in too. Or do I HAVE to find that wire that comes out of the back of the fuse panel and tie into that one? It'd be much easier to not go that route.

I was reading some posts on this and Roger said he had to put on a female connector because the early switches didn't have one. But the switch I have (old and new) do have that already in.
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Michael
'77 1/2 924 N/A- 5 speed Audi box
'04 Ford Taurus - gone!!
'92 Jeep Cherokee Laredo - gone!!

Porsche... better than tea with Miss McGill
(Slap Shot)

[Smoothie]

Have a look at the wiring diagrams. For '77.5, the red wire off the end of the ign switch (post "Su") leads to post 85 of the seat belt warning relay.

Yes, I'd say tap into that red wire, but don't use it to power the sound system directly. Later cars got a "radio relay", and you can do something similar with a standard automotive relay - rated somewhere in the 20-30 amp range. You'd use power from that red wire to activate (pull-in) the relay (relay posts 85-86), and have 12V+ from an always-on 12v+ source* running through the switch portion of the relay (posts 30-87 (normally 30 connects to the source, and 87 would go the the radio - though it doesn't matter and would work in either direction)).

*- ideally taken from an "H" terminal on back of the fuse-relay panel, else directly from the battery.

The reason for using a relay is so you're taking a very low current from the ign switch to switch radio power on/off, while actually running the larger current needed to operate the sound system through beefier wiring and connectors. -Thus avoiding meltation of the ign switch...
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[mgatlag]

Very cool, thanks Smoothie. Can I just use 12 Gauge wire for everything? I have lots of it left over. I also have one terminal still not spoken for on the ground cluster behind the fuse box so I can ground the relay there I suppose. And can I pull power from the cig lighter or clock for my other constant power source on the relay?
_________________
Michael
'77 1/2 924 N/A- 5 speed Audi box
'04 Ford Taurus - gone!!
'92 Jeep Cherokee Laredo - gone!!

Porsche... better than tea with Miss McGill
(Slap Shot)

[RC]