Dimmer knob wiring/functioning

[Sukhoi]

I put an aftermarket cruise control system in my gf's car, and I am trying to use the dimmer knob wiring to make the cruise light up when the parking lights go on. First I hooked it up to the dimmer wire that gets +12 VDC constant when the lights are on, but the cruise lighting was working backwards. If I turned the dimmer so the speedometer was lit the cruise was dark, and if i turned the speedometer dark then the cruise lit. I thought for the heck of it I would try the other wire, and that gives me no lighting on the cruise control at all.

Is there any other way to hook to the dimmer switch I'm not thinking of? I don't want to tear the steering column apart trying to find the parking light wire. If that's the case I'll just leave the cruise control dark. 😛

 

[boomerang]

If I understand correctly (and I may not), you need to splice into the output wire from the dimmer not the +12V feed. What you are doing is providing a ground path for that circuit that has less resistance than the dimmer.

Find the output that has variable voltage as the dimmer cycles and that will be the wire you want.

Where to find it, I can't tell you. You're not saying what car it is, but personally it wouldn't make a difference to me. Unless you could find a wiring diagram to link to, I wouldn't be able to tell you which wire you need.

I doubt this helps but it's all I've got.

Edit: I've got more. 😀 There will be a connector under the dash near the column that will have the wire or wires in it that power the parking lamps. With a test light or multimeter you should be able to tell which one it is. It may be a chore because there's probably a lot of wires in that connector. I can't imagine you'd have to tear the column apart for that.

 

[Sukhoi]

Heh I suppose I should have mentioned the car. 2003 Echo.

The variable-voltage wire should be one of the two connected to the dimmer, right? Unfortunately I've tried both and neither work. The one leaves the cruise dark, and the other lights the cruise opposite to the dash.

 

[boomerang]

Originally posted by: Sukhoi
Heh I suppose I should have mentioned the car. 2003 Echo.

The variable-voltage wire should be one of the two connected to the dimmer, right? Unfortunately I've tried both and neither work. The one leaves the cruise dark, and the other lights the cruise opposite to the dash.

It sounds like the dimmer provides a path to ground. So when you are getting nothing you are tapping into the ground. When you get the opposite from what you want you are providing the ground as I said earlier. In other words, what we both thought is a +12V will actually vary depending on the setting on the dimmer. There is a +12V feed to the lights and the ground for those lights is provided through the dimmer. Does this make sense after all my edits?

We were both typing at the same time. Read my edit in my previous post.

 

[Sukhoi]

I hadn't thought about a connector down there...good idea. Maybe I will look for that tomorrow. I suppose I can try to see what color wires are physically connected to the parking lightbulbs, and then try to find those wires inside the firewall.

 

[boomerang]

Originally posted by: Sukhoi
I hadn't thought about a connector down there...good idea. Maybe I will look for that tomorrow. I suppose I can try to see what color wires are physically connected to the parking lightbulbs, and then try to find those wires inside the firewall.

Yes, good plan. They may change color as they go through the connector at the firewall, but that would be really unusual. Highly unlikely I would think.

Post back with your results.

Edit: I made a really awesome diagram. 😉 You probably don't need it to understand the circuit, but I'd hate to waste it. 🙂

Dimmer Circuit