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2G Defroster to toggle switch

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Turbodhi

Proven Member
115
10
Oct 18, 2015
Olathe, Kansas
Hey guys,

I removed the HVAC controls in my car but is like to retain the front defroster. I can manually set the ducts to blow on the front window but in not sure how to wire the fan to a toggle switch. I'd like to do it properly. Any advice would be appreciated.

Thanks!
 
- Is this a 4g63T or 420A or ???
- MT or AT?
- Do you still have working AC?
- I can tell you how to wire a toggle switch in (in place of the selector switch for just full speed) but w/o working AC your windshield will just fog up in winter and when it's raining.
- If you don't have working AC you still want me to tell how to add a toggle switch to the blower (to replace the selector fan speed switch)?
 
Last edited:
It's a 4g63T
Manual
I removed all AC components and the selector switches(everything under the hood). I still have the under dash unit, vents, heater core etc.

it already fogs up in cold rainy days, but I really just need something to help with removing ice in the winter and to keep it from freezing on the inside on my way to work.
 
To just run the blower (on full speed) with no AC, (and assuming blower motor relay is still connected) either 1) connect the blower motor black/yellow wire to a toggle switch with other side of switch to ground or 2) connect the blower switch (8 wire connector) black/yellow wire to a toggle switch with other side of switch to ground.
 
Maybe im misunderstanding something but both of those options look like the same thing.
 
There's a lot of current load through the blower motor on high speed. So make sure your toggle switch is high amperage or, the better way, is to run the blower motor off a relay. Relays are much better at handling high current situations. So in that case, key on power to one leg of the relay, your toggle switch to ground on the other side, then fused 12V power to the switched side of the relay with the supply to the blower motor on the other side. If you're gonna just run a toggle switch, I'd definitely put the switch on the ground side of the blower motor. Controlling the ground side will put less current through the switch and keep you from melting it in the long run. That's how I had it setup in my car for a very long time. It works well with the heat on in winter /snow, but rain it's very likely to just keep fogging up.
 
There's a lot of current load through the blower motor on high speed. So make sure your toggle switch is high amperage or, the better way, is to run the blower motor off a relay. Relays are much better at handling high current situations. So in that case, key on power to one leg of the relay, your toggle switch to ground on the other side, then fused 12V power to the switched side of the relay with the supply to the blower motor on the other side. If you're gonna just run a toggle switch, I'd definitely put the switch on the ground side of the blower motor. Controlling the ground side will put less current through the switch and keep you from melting it in the long run. That's how I had it setup in my car for a very long time. It works well with the heat on in winter /snow, but rain it's very likely to just keep fogging up.

It's been a busy week so im just now able to sit and think about this. I made the crappy diagram included. Let me know if I need to tweak some stuff.
 

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So the blower motor should still be fused from the factory harness but the switch I install will need one too. Is there a power rating I need to stay in range of with the switch and fuse?
 
In the schematic I posted, that's assuming you're disregarding the factory harness all together. Unless you de-pin the KO power and blower supply from the big connector that goes to the HVAC control head.
 
In the schematic I posted, that's assuming you're disregarding the factory harness all together. Unless you de-pin the KO power and blower supply from the big connector that goes to the HVAC control head.
Ok so I bring 2 separate 12v source from the battery. One to the switch side of the relay and one to the blower side. 10A fuse for the switch (I got that number from some reading) and 30A for the blower. The relay is rated to 30A. Which should be max max for the blower on high setting. At this point I need to know what wire on the blower to attach to the relay and which one to attach to ground.
 
Ok so I bring 2 separate 12v source from the battery. One to the switch side of the relay and one to the blower side. 10A fuse for the switch (I got that number from some reading) and 30A for the blower. The relay is rated to 30A. Which should be max max for the blower on high setting. At this point I need to know what wire on the blower to attach to the relay and which one to attach to ground.


Pretty sure it's gonna be the black with yellow at the blower for power. That leaves the other for ground. If you have a power probe, you can supply power and ground to the motor and see what does what. I'd definitely keep the factory blower connector. Just cut the wires and connect your wire setup to them.
 
Pretty sure it's gonna be the black with yellow at the blower for power. That leaves the other for ground. If you have a power probe, you can supply power and ground to the motor and see what does what. I'd definitely keep the factory blower connector. Just cut the wires and connect your wire setup to them.
So far so good! I just need to pick up some thicker gauge wire from the auto parts store and wire up the actual blower then I'll be done.
 
U
Pretty sure it's gonna be the black with yellow at the blower for power. That leaves the other for ground. If you have a power probe, you can supply power and ground to the motor and see what does what. I'd definitely keep the factory blower connector. Just cut the wires and connect your wire setup to them.
Update!!

The second schematic worked! The blue cable is power the black and yellow is ground.
 
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