Help reading this wiring diagram

[CyFi6]

So im trying to figure out this wiring diagram and need some help. This is the rear window defogger circuit.
http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=084

The trouble i am having is understanding the defogger switch. It is labeled "with timer" and "w/o timer", and i am wondering, is this how the actual switch, or are there two different circuits in the switch labeled that i cant tell apart. Also, i am wondering how the switch works, i do not understand. You can push the switch up momentarily to turn on the defrogger, and once the key is cycled off an back on, the switch is no longer on. How does this circuit work and can i immitate it using a regular momentary push button switch?

Also, how do i know if i have a timer in my switch or not, and is it possible to dismantle it and bypass the timer so it is always on? The reason i ask these things is because i want to use a defogger switch for a different circuit, but i need it on all the time and cant have it turn off until i cycle the key off. THanks a bunch for any help.

Also, do all supras have heated mirrors? How do i know if i have them or not?

 

[Kckazdude]

I havent seen a defroster switch that didnt have a timer in it. The way the switch is assembled I can tthink of a way to mod it to work like you are wanting. The best I can think of it to build you a custom switch panel and install your own rocker switches.

 

[isnms]

Just use a fog light switch.
Buy one off a part out. It fits switch panel.

 

[CyFi6]

i dont want an on off switch though. I want a switch that turns on when you turn it on, but automatically turns off when the key is turned off, but not back on when the key is turned back on, just like the defogger switch does.

If i understood how the switch worked i might be able to disable the timer

 

[figgie]

Ok just to clarify.

That timer / wo timer switch is actually the same switch and has always been with timer.

 

[CRE]

Google "latching relay".

 

[jetjock]

There were three types of switches used by Toyota during those days for defogger operation:

1) Switch with no timer

2) Switch with IC timer

3) Switch with discrete timer and cancel function.

The MKIII uses # 3. Timing is done by charging a 220 mf capacitor (C2) in an RC network that keeps a darlington pair on as long as it takes for C2 to bleed down. The darlingtons in turn energize the defogger relay. Pressing the cancel side of the switch discharges C2 to ground and shuts the transistors off. I'll leave it up to you to figure a way around that.

Easier is to use a NO momentary button of your choice and a double pole relay configured for latching to get what you want. The stock defogger switch can be modded for use in that application or you can use a fog light switch as suggested but you'll either have to make it momentary or remember to cycle it on then off...or off then on the next time you start the car.

 

[CyFi6]

Thank you guys for all your help. I did some testing with the cruise control switch which works similarly to the defogger switch but does not have a timer. I opened it up and figured out which point gets power when the relay is energized, so i will use a new cruise control switch and run a relay off of this said point. That way whenever the cruise is latched on, my accessory will be, and whenever its off, my accessory will be too.