Electrical Defrost switch ignition?

Teen'93stang5.0 · May 16, 2026

I was watching the BigTime guys fight with their ‘89 GT on YouTube and noticed they somehow have the defrost switch hooked up as a starter switch.

I was wondering if this was just some custom thing that the previous owner did (they never mention it in the episodes), or if this is a pretty common thing? Anyone ever seen or heard of anything like this?

AeroCoupe · May 16, 2026

Not in 25+ years of messing with these cars have I seen that. Not saying bad or good about it as that depends on how they wired things.

Noobz347 · May 16, 2026

I have my defrost button setup to activate Machine Guns.

gkomo · May 16, 2026

Love watching those BigTime guys. Can’t wait for their next video fixing the Fox (or did they already do that?) last I remember they blew up the motor.

General karthief · May 17, 2026

I don't have de-frost.
Or machine guns
I do have a fox......where'd I park that thing?

Teen'93stang5.0 · May 20, 2026

Well, would I be completely an idiot if I assumed that just routing the ignition wire through a momentary switch in the dash would work? It doesn’t negate the need for a key, but a little quirk and maybe even a little theft protection could be worth it.

Noobz347 · May 20, 2026

Teen'93stang5.0 said:
Well, would I be completely an idiot if I assumed that just routing the ignition wire through a momentary switch in the dash would work? It doesn’t negate the need for a key, but a little quirk and maybe even a little theft protection could be worth it.

Correct. You would wire the defrost switch in to trip a relay beefy enough to send power to whatever it is you want to power.

By the same token, you could leave your key switch intact and use the defrost switch to power/disable the start relay.

So, your ignition sequence might be something like this:

Key ON
Defrost Switch Pressed and Released
Key to START

Without the momentary press of the Defrost Switch to close the power relay to the start solenoid, you'd get nothing. Not even a click.

You could then use the Defrost Light to indicate whether the Start Solenoid Power Relay was energized or not energized.

I mean... There's lots of ways you could do it.

Teen'93stang5.0 · Wednesday at 7:31 PM

the dash is gonna have to come out sooner or later, so whenever that is I’ll do some creative wiring in there

Noobz347 · Wednesday at 7:50 PM

Teen'93stang5.0 said:
the dash is gonna have to come out sooner or later, so whenever that is I’ll do some creative wiring in there

Just remember to draw yourself a wiring diagram so you can remember what the hell it was that you did X many years ago.

Teen'93stang5.0 · Wednesday at 8:38 PM

Noobz347 said:
Just remember to draw yourself a wiring diagram so you can remember what the hell it was that you did X many years ago.

This sounds like speaking from experience

Electrical Defrost switch ignition?

Teen'93stang5.0

AeroCoupe

lube between the nut and the face. I know my lubes

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

gkomo

now i can hopefully expect to receive the shaft

General karthief

wonder how much it would cost to ship you a pair

Teen'93stang5.0

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

Teen'93stang5.0

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

Teen'93stang5.0

Similar threads

Electrical Defrost switch ignition?

lube between the nut and the face. I know my lubes

Stangnet Facilities Maint Tech... Er... Janitor

now i can hopefully expect to receive the shaft

wonder how much it would cost to ship you a pair

Stangnet Facilities Maint Tech... Er... Janitor

Stangnet Facilities Maint Tech... Er... Janitor

Similar threads

Privacy & Transparency

Privacy & Transparency