A/C on with Defrost

Just throwing this out there but after this wire is cut could it instead be used to trigger the heated mirrors for those of us who have done or are considering that mod?

 

Clever idea TacomaDad.

But I don't think this would be straight forward. The green wire outputs different voltages depending on the air-vent-mode selected per the table below.

0V Defrost
3V Defrost-Feet
6V Feet
9V Feet-Vent
12V Vent

I assume you only want to trigger the heated mirrors when one of the defrost modes is selected (0V or 3V). But I'm not sure how one could easily build a circuit with a trip point between 3V and 6V (or between 6V and 9V if the polarity is reversed)? I doubt 12V relays opperate at that voltage range, and I don't know if their hysteresis is that tight (this would all be easy to prove experimentally though). Also, you might have to figure out how much current the green wire can supply without letting any magic smoke out of the servo motor amplifier (my guess is it's just a simple restive voltage divider).

My two cents.

 

super easy mod......except for the fact that i can't get the green wire to release. i guess i'll just keep the defroster stock for now. i'd hate to force it and break something.

 

tag for when i get my truck back

 

Great mod, a way to save gas for free.

 

Can't wait to do this mod this weekend, when I have some daylight.

 

just got out and did mine, glad i found this thread cause i hate car's that automaticly turn the AC on with defroster, i like to leave all of my cars on floor/defrost and now i can leave the truck set like this

edit, this should be stuck in the mods sticky if it isn't already!

 

This, along with a lot of other mods are posted in the Cheap/free mods thread.
Cheap/free mods

 

I assume most of you folks doing this mod already know this, but I'll add it for those who don't. There are two reasons that the AC is linked to the defrost:

1. Running the air through the condenser first dries it as well as cooling it, so there's less humidity in the air being forced onto the windshield.

2. You need to run the AC periodically so that the seals don't dry out, crack and leak.

 

That's great, but try heating your truck up and thawing the windshield in below zero temps with the AC running. Air's pretty dry at that temp already, and cooling the air before heating it isn't going to help anything. I think a good portion of the people doing this mod have weather like that. Or are really trying to squeeze out more MPG's.

Oh, and if you're idling the truck to warm up/clear windows in winter this "feature" wastes more gas. You have to idle longer for the air to warm up and clear windows if it's on, and more load on the engine.

Personally, I just leave the selector on the top position (feet) since it sends air to the feet, windshield, and side vents to clear the windows. Only flip it past the top option when it's humid out and I need the AC to dry the fog on the windshield. Even then I need to play with the temp as too cold makes fog form on the outside of the windshield.

 

so i have an interesting comment on this ( i think) got my truck brand new in 07 and since i can remember my a/c button always allows me to turn the a/c on/off during defrost no matter what section its on, feet, windshield or both. any thoughts?

 

Yes the button does turn the compressor on & off in all positions - except the defrost. The compressor comes automatically when the defrost is on. The light on the button does not light up though.

If you listen carefully, or if you have the truck in gear, you can hear it or feel it come on.

GA

 

That's weird... I literally just did this on my first gen. The funny thing is, on the 1st gen all you have to do is take the knob off and turn it past defrost... voila! Defrosting without A/C. Oh the joy of the simple 1st gen

 

I think my 2011 does this, no light but cold air was blowing

 

ahhh yea makes sense. i have felt it before but usually im inside the warm house hitting the remote start button in the morning

 

Just did the mod. Will let you know when I start her up tomorrow. Thanks for the write up on the 09s and up!

 

i know this is a dumb question but were would the servo be on a 98?

 

Well this answers my question on whether anyone figured out how to do this on '10 models. Now I just need to read back and find it.

This whole A/C linked defrost idea might work in the south or warmer states, but here in New England we need our defrosters to blow HOT air. Forcing this on us was not thought out at all by Toyota engineers.

 

Have you tried have the selector on the feet only position? I live in NY with ice and snow, and that works fine for me. Once the engine is warmed up if I really need to melt ice and clear the windshield the windshield-only position with the AC works fine too. It was -15f last week for 2 days when I drove into work. No problems there. Had to let the truck idle to warm up before leaving anyway, and being that cold my breath kept fogging the windows so the AC helped clear them. Even with the feet only position enough hot air hits the windshield to melt ice off the wipers. It even clears the two front side windows, blows along the floor and 2 of the front vents to warm the cab. I never use windshield only unless the windows are fogged on the inside.

 

I would say if your window isn't clear you need to stop driving. Planning to sue will never work out. Im sorry the defrost isn't strong enough but please don't continue to drive if you do not have a clear view. When you run over some kid how is a law suit going to bring their life back?