Defogger operation

[Bitsyncmaster]

I was looking at the defogger circuit. If you want the indicator light to come on when the defogger is powered, you can just rewire that light wire from the switch to the defogger relay pin #3 (normal relay pin would be pin #30). That is the output pin that drives the defogger.

I measured the current of the defogger:
12.6 volts = 6.9 amps
14.5 volts = 7.9 amps

Power is supplied by fuse #9 which also power the mirrors (and mirror heaters if you install them). The recommended 10 amp fuse could be close to blowing if you have the defogger on and run the mirrors. Would definitely blow with mirror heaters running with the defogger.

I think I will use my fan relay with different software to replace the OEM (green relay). I will have to swap the ground and control pins around in the socket. I guess all I need it to do is power the defogger on for 5 minuets when it first gets powered.

[Bitsyncmaster]

A standard relay would work in the defogger socket but you would not get the cycling on and off of the OEM relay. I guess they had to swap the ground and control pins to fit their circuit board into the unit (that's why it's so tall). To use a solid state relay you need to put the ground and control pins back to the standard pin configuration.

[Bitsyncmaster]

Now I guess I need to wrap my harness to finish things up.

I was able to feed the new light wire up to the defogger switch without pulling the center console.

[Christian Dietrich]

Hey buddy, so you designed a solid state relay for the rear defogger or is this if you run heated mirrors along with the rear window? I have convex mirrors but thinking of changing them out to heated mirrors, and i'm guessing that what this solid state relay does?

[Bitsyncmaster]

Hey buddy, so you designed a solid state relay for the rear defogger or is this if you run heated mirrors along with the rear window? I have convex mirrors but thinking of changing them out to heated mirrors, and i'm guessing that what this solid state relay does?

I used my fan relay and programed it to turn off after 5 minuets. I rewired the fogger lamp to the output of the relay. If I had a momentary switch for the fogger, I would program it to use that but for now it just uses the stock switch. So I can turn it off with the switch or wait for the 5 minuets to time out. If I leave the fogger on it would turn on again when I start the car up. But the fogger lamp would show me that it is still on.

You can run a standard relay and it will work with the basic full on or full off. The OEM relay cycles power after it is on a while. That also would let you run the lamp on the output.

[Christian Dietrich]

I used my fan relay and programed it to turn off after 5 minuets. I rewired the fogger lamp to the output of the relay. If I had a momentary switch for the fogger, I would program it to use that but for now it just uses the stock switch. So I can turn it off with the switch or wait for the 5 minuets to time out. If I leave the fogger on it would turn on again when I start the car up. But the fogger lamp would show me that it is still on.

You can run a standard relay and it will work with the basic full on or full off. The OEM relay cycles power after it is on a while. That also would let you run the lamp on the output.


So, your defogger circuit now powers the back glass and the mirrors using the original switch? If I read that right ofcourse.

[Bitsyncmaster]

So, your defogger circuit now powers the back glass and the mirrors using the original switch? If I read that right ofcourse.

It could if you wire the mirror circuit to the defogger circuit. I never really thought or looked for the mirror heating circuit. If I had heated mirrors, I would wire it like that.

Edit:
I just looked at the schematic and stock wiring, the mirrors are powered all the time. So you would want to move that circuit to the output of the relay. The OEM relay would cycle the power like the rear glass so you probably want to use a standard relay.

I would also power the relay with fuse #9 so the switch does not have to carry all that current.

[Christian Dietrich]

It could if you wire the mirror circuit to the defogger circuit. I never really thought or looked for the mirror heating circuit. If I had heated mirrors, I would wire it like that.

Edit:
I just looked at the schematic and stock wiring, the mirrors are powered all the time. So you would want to move that circuit to the output of the relay. The OEM relay would cycle the power like the rear glass so you probably want to use a standard relay.

I would also power the relay with fuse #9 so the switch does not have to carry all that current.

Doesn't sound to difficult to do other than finding the wire in the fuse box area.

[Rhye]

The mirror adjustment will obviously work only with defogger switched on if you do that.


Doesn't sound to difficult to do other than finding the wire in the fuse box area.

[Bitsyncmaster]

The mirror adjustment will obviously work only with defogger switched on if you do that.

Mirror adjust and mirror heaters are already wired to fuse #9. Wiring fuse #9 to power the defogger relay and moving the heater wiring to the output of the relay would not add the heater current through the defogger switch and even power the defogger not through the switch.

I don't know what the current of the mirror heaters is. My guess would be an amp or two each. Quite a useless load when not needed.

[Rhye]

Mirror adjust and mirror heaters are already wired to fuse #9. Wiring fuse #9 to power the defogger relay and moving the heater wiring to the output of the relay would not add the heater current through the defogger switch and even power the defogger not through the switch.

I don't know what the current of the mirror heaters is. My guess would be an amp or two each. Quite a useless load when not needed.

Correct. My point was that there's only one "hot" wire (fuse #9) coming to the door (mirror switch) so you'd need to route an extra one if you want to power mirror heaters (if fitted) from defogger circuit (unless there's a spare one in the roof harness, but I can't recall that).

[FABombjoy]

I have my heated/convex mirrors wired this way - needing to turn on the rear def switch for heat and adjusting. For me it was pretty much set and forget, so having mirrors on the defroster switch isn't a big deal.

In practice convex mirrors rarely need adjustment. Because the mirrors are so deep in the housing, adjustments mainly change how much of the housing is visible along the edges, but has little affect on how much road you can see. With factory flat mirrors it was more important.

Once in a while I try to adjust the mirrors then remember not much actually changes. If the mirrors were flush to the edge of the housing then adjusting them would probably be more useful.

[Bitsyncmaster]

I wrote new code for my defogger relay. It now can work plug and play (same as using a normal relay) or with some wire changes it can work with a momentary push button to turn it on or off. If I can somehow get a new switch cap with a defogger logo to use with the DMCH lighted window switches I will replace my current defogger switch with that. My current one is the SPST smaller switch used on another car.

I already wired the defogger light to the output of the defogger relay. I would need to wire the power input pin to an AUX relay.

Then using a momentary switch, push once to turn on the defogger for 5 minuets. Push again would terminate an already on defogger. Works like new cars.

Not that I ever use the defogger but would like the lighted switch.

[Bitsyncmaster]

I wired the relay power input pin to green/white wire feeding the power to the defogger switch. Easier to do splices anyway under the ash try. I'm still thinking what I can do to change the translucent decal on the DMCH window switch.

[Bitsyncmaster]

I've been busy putting lattice up under my front porch so things have mostly stopped with the D. I did however 3D print a switch cap for the DMCH window switch to use the momentary switch for my rear defogger. I hope it will also work illuminating the "decal" 3D printed in the cap.

I need to pull my center console to replace the switch because I had glued in the switches (before the vendor plates came out).

[Bitsyncmaster]

Not perfect but pretty good for now. Maybe we can convince DMCH to produce a new switch cap to use with their lighted window switches. My defog unit will work with the normal on off switch but you need to wire the defog light to the output (defogger circuit) so you can see when it shuts off after 5 minutes. I built this for two reasons. One was to get a lighted switch, the other is to get that tall green defogger relay gone. Now every relay are now my solid state relays.

It took quite a lot of work getting the switch cap built. I used the .STL file someone had already done but removed some of build used to actuate the stock switch. I then had to build up the inside of the cap with epoxy to get proper switch operation. I used V4 resin which is not as flexible as the injection molded caps. So I had to sand the clearance so as not to break the cap when pushed onto the switch. I would use a little less white dye on the decal infill. Mine is not quite as translucent as the DMCH window switch cap.

Here is a video of it working.

https://youtube.com/shorts/YPuasehnRps?feature=share

[Bitsyncmaster]

Here is my relay compartment. Now what am I going to design?

[dmc6960]

Looks amazing Dave, love it!
+1 on using a momentary rocker for activation as well. Who the heck puts a hard on/off switch on a timed circuit?

Do a new wiper delay module next!

[Bitsyncmaster]

Looks amazing Dave, love it!
+1 on using a momentary rocker for activation as well. Who the heck puts a hard on/off switch on a timed circuit?

Do a new wiper delay module next!

Now that's an idea.

[Timeless]

Now that's an idea.

:thumbup2:

[Bitsyncmaster]

Ran across this note when cleaning the garage. If you want to use the DMC window switch as a momentary switch, and you want it to work both directions, you need to use diodes for the two load outputs when you tie them together because those outputs ground if not turned on.

Switch pin number

1) Load
2) Ground
3) +12 volts
4) LED power
5 Load

Just wanted to document this.