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fire_fly88

Dimmer Switch Momenary Switch

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I have been reading on the forum of people who have changed the usless dimmer switch to activate fog lights. What I cannot figure out is that the dimmer swith is a momentary switch (it is only on when you are pushing the button) so how do they control the fog lights and get them to stay on like a typical toggle switch? Thanks for your help.Calvin

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Latching relayLatching relay with permanent magnetA latching relay has two relaxed states (bistable). These are also called "impulse", "keep", or "stay" relays. When the current is switched off, the relay remains in its last state. This is achieved with a solenoid operating a ratchet and cam mechanism, or by having two opposing coils with an over-center spring or permanent magnet to hold the armature and contacts in position while the coil is relaxed, or with a remanent core. In the ratchet and cam example, the first pulse to the coil turns the relay on and the second pulse turns it off. In the two coil example, a pulse to one coil turns the relay on and a pulse to the opposite coil turns the relay off. This type of relay has the advantage that one coil consumes power only for an instant, while it is being switched, and the relay contacts retain this setting across a power outage. A remanent core latching relay requires a current pulse of opposite polarity to make it change state.

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Hi Calvin,It's not actually a momentary switch. Huronlad has described it well. When you press the switch and release, it has dimmed the lights, and they will stay dimmed unless you press and release the switch again or unless you turn off the car, interrupting power to the switch.So when you re-purpose the switch for fog lights (or whatever) I suppose it will work similarly: switch on the fogs and then switch them off manually, or they will switch themselves off when you turn off the car. Kind of cool...Bil :sun:

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The switch consists of a small circuit board with two connector pins and a tiny push button switch. So what you are telling me is there is a latching relay somewhere that keeps the state of the switch and the momentary switch simply activates the relay. Where is this relay located?

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It is just an input to the computer. The computer will change state of the output, and stay that way until it receives another input pulse, or until the power is removes and the computer reverts back to it's default state.A latching relay can be added to change the way the switch functions, or the computer could be reprogrammed if that is possible. An entirely separate add-on latching relay is much easier to add foglights. Some European smarts are available with factory fogs, so the function is there through the light stalk and could be added that that way.

Edited by Alex

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I'm getting confused!When I wired up lights in the fog light light position here's what I did.First the turn signals have to be wired to the euro position. Then behind the fog light postion there is a wiring connector taped to the frame. That can be plugged right to the oem fogs.Then I popped out the dimmer switch and disconnected the plug. Over on the right will be the fog light plug. Plug that into the dimmer switch and your good to go. Turns on and off the fogs.No more dimmer function.There is a fog light switch available that has a led indicator light on it.

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There you go! The computer function and the wiring is already there. My mistake, I thought the OEM fogs were controlled from the light stalk, but I now believe Uncle Glenn. The existing switch is used to control a different computer input, that in turn switches on and off the output to the harness already in place but not connected to anything. The cars with the OEM fogs would have had a second switch beside the dimmer.I like the dimmer, I get out of town at times with a long night-time highway drive and it's nice to have a dim dash, also I have a screen section to cover the door window over the driver-side mirror so an over-taking car doesn't blind me. The passenger side just gets turned out, the inside has its night position of course, so my night vision stays keen.

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Maybe I should be more specific, I am not actualy hooking up the fog lights, I just wanted to use the dimmer switch to activate an emegency light that I wired onto my windshield behind the rearview mirror. I think the easy thing to do is to change out the whole switch.

Edited by fire_fly88

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Then swap the switch to the harness for the OEM fogs, find the fogs output wire (Evilution has wiring diagrams) and use that to power your light.

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The dashboard lights don't "dim" on the EU/international fortwos; that's a Canadian function, and EU cars only have the one fog lamp switch (or a blank). The PCB inside the "dimmer" switch is identical to the fog lamp switch, minus the LED SMD. It even says "Nebelscheinwerfer" ("fog lamp") on it.On the other hand, I am looking for a latching circuit to turn off my angel eyes when I activate the turn signals. Right now I only have a simple relay that wig-wags them. Because the turn signals work off a CAN signal, I can't figure out how to power a latching circuit.

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On the other hand, I am looking for a latching circuit to turn off my angel eyes when I activate the turn signals. Right now I only have a simple relay that wig-wags them. Because the turn signals work off a CAN signal, I can't figure out how to power a latching circuit.

Run each angel eye through a small 12 volt relay that is controlled by the turn signal on the same side. Turn signals lit, angel eye off. then put a polarized capacitor across the relay, large enough to keep the relay energized for the time that the turn signal is out. You may need to include a diode in series with the capacitor.

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