Fog Light switch/Defroster switch question.

[BobSacamano]

I got an Explorer Defroster switch. Looks just like the fog light switch and is in better shape. So my question is, Can I use the defroster switch in place of the fog switch? I guess defrosters only stay on for a short while but is that from the switch or maybe the relay? Anyone ever done that?

 

[Curious Hound]

When you say defroster switch, are you talking about the switch for an electric rear window defroster?

if so, i don't think that will work. I believe that is a momentary switch. That means that to use it for fog lights, you would have to hold it down for the whole time you want the lights on.

or, you would have to build a circuit with relays to keep the circuit on after you let go of the switch.

 

[BobSacamano]

Thanks for the reply. Yeah I figured it wouldn’t work but thought I’d ask.

 

[BobSacamano]

When you say defroster switch, are you talking about the switch for an electric rear window defroster?

if so, i don't think that will work. I believe that is a momentary switch. That means that to use it for fog lights, you would have to hold it down for the whole time you want the lights on.

or, you would have to build a circuit with relays to keep the circuit on after you let go of the switch.

The GEM/CTM controls the heated backlite and mirror timer. When the rear window defrost switch is pressed, a ten-minute timer is started and the GEM/CTM energizes a relay that provides battery voltage to the heated backlite (and the heated outside rear view mirrors, if equipped).

The GEM/CTM de-energizes the relay when either ten minutes have elapsed, the rear window defrost switch is pressed again, or the ignition switch (11572) is turned to OFF or ACC. The ten-minute timer is temporarily halted if the ignition switch is turned to START, and resumes after the ignition switch is returned to RUN.


I just saw this. Maybe the GEM makes it momentary, not the switch? I opened up the defroster and fog switches and they look the same. I moded the defroster switch with blue LEDs and put a fog button on it. To satisfy my curiosity, I may just have to try it.

 

[Curious Hound]

The GEM/CTM controls the heated backlite and mirror timer. When the rear window defrost switch is pressed, a ten-minute timer is started and the GEM/CTM energizes a relay that provides battery voltage to the heated backlite (and the heated outside rear view mirrors, if equipped).

The GEM/CTM de-energizes the relay when either ten minutes have elapsed, the rear window defrost switch is pressed again, or the ignition switch (11572) is turned to OFF or ACC. The ten-minute timer is temporarily halted if the ignition switch is turned to START, and resumes after the ignition switch is returned to RUN.


I just saw this. Maybe the GEM makes it momentary, not the switch? I opened up the defroster and fog switches and they look the same. I moded the defroster switch with blue LEDs and put a fog button on it. To satisfy my curiosity, I may just have to try it.

No. The switch gives a momentary signal to the GEM to start the timer.

If the switch was continuous, the timer would automatically restart every time the timer is finished. The fact that you have to push the switch again to restart the timer proves that the switch is momentary.

 

[BobSacamano]

So if you took the GEM and timer out of the equation, wouldn’t the switch stay on until you turned it off?

 

[Curious Hound]

So if you took the GEM and timer out of the equation, wouldn’t the switch stay on until you turned it off?

No. It is a momentary switch. It would only be "on" as long as you hold it "on" with your finger. As soon as you let go, it releases and turns off.

It's like pushing the "2" button when you get in an elevator. You push the button and let go. That starts a series of electronic events in the controller. As soon as that series of events (close doors, run the motor until it reaches the second floor, stop motor), is finished, everything stops until another button is pushed. The circuit remembers that you momentarily pushed a button. Then it forgets when the task is finished. You don't have to hold the 2 button the whole time. In fact, the circuitry or computer program ignores all other pushes of the 2 button until such a time as the elevator car is not on the 2nd floor and the button is pushed again.

 

[BobSacamano]

Ok. Thank you for the explanation.

 

[Curious Hound]

In your case, you push the button once. The GEM starts the timer and energizes the rear window defroster and it remembers that you pushed the button until the timer is done. When the 15 minutes us finished, it stops the heater and resets the timer back to 0.

 

[SenorNoob]

It might possible to convert it to a toggle switch... Probably more work than it's worth unless you are bored. Some momentary switches are the same as their toggle counterparts except for an added spring. It might end up missing the latching function then and just kinda flop off and on. Gotta use a little mechanical logic.

 

[Curious Hound]

My recommendation is; " Just buy the right switch and do it right." It's much simpler, easier and quicker than trying to rig something else.