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I'm hoping someone knows which wire I can "modify" to disable the a/c compressor from coming on automatically when defrost is selected and only come on when I push the button. I know there's certain times it's beneficial to use but I think I'm capable of deciding that for myself :confused:
 

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marcat75 said:
I'm hoping someone knows which wire I can "modify" to disable the a/c compressor from coming on automatically when defrost is selected and only come on when I push the button. I know there's certain times it's beneficial to use but I think I'm capable of deciding that for myself :confused:

You don't really want to do that. It coming on serves two purposes that I know of. One, it helps to remove the moisture from the air which aids in better defrosting and prevents frost/ice inside. Two, it helps to keep the ac unit lubricated and functioning thus the seals don't dry out preventing leaks and the unit doesn't seize up.

Good luck if you find a way to do it.
 

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Heatstroke said:
You don't really want to do that.
Yes - I do really want to do that :) Have background in hvac, EPA refrigerant certified Univeral & Section 609, blah blah blah. Hence: "I know there's certain times it's beneficial to use but I think I'm capable of deciding that for myself" Also I've had no problems on previous vehicles that didn't have the compressor tied-in to the defrost switch because I knew when to use it. But yes I guess I'd agree that if someone doesn't know/can't remember to run the compressor every now and then they shouldn't disable it (hopefully they will have the need to run defrost).
IMO - I think the automakers were getting owners who didn't/wouldn't read the owners manual complaining that the defrost wasn't clearing the windshield so the automakers re-designed to accomodate for those people, kind of like idiot lights instead of guages.
If I had the wiring diagram I'd figure it out myself and post it, with a disclaimer of course for those that require that sort of thing.;)
Nothing personal, just didn't want others thinking I didn't really want to do it anymore and not post the answer if they have it.
 

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marcat75 said:
I'm hoping someone knows which wire I can "modify" to disable the a/c compressor from coming on automatically when defrost is selected and only come on when I push the button. I know there's certain times it's beneficial to use but I think I'm capable of deciding that for myself :confused:
(sorry huge picture)


K here's how to do it, if you pull your climate controls out on the right hand side there is a wire I think it is brown on my truck (2000) Just disconnect that harness and the AC will not come on with the defrost. (see green circle in picture below)

Just out of curiosity why do you want to disconnect it? The ECU disengages the AC clutch under hard acceleration and some other situations.


edit: hold on I am resizing pic, way too big.
 

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akshunj said:
(sorry huge picture)


K here's how to do it, if you pull your climate controls out on the right hand side there is a wire I think it is brown on my truck (2000) Just disconnect that harness and the AC will not come on with the defrost. (see green circle in picture below)

Just out of curiosity why do you want to disconnect it? The ECU disengages the AC clutch under hard acceleration and some other situations.


 

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Discussion Starter #6
Thanks for the tip!

akshunj said:
Just out of curiosity why do you want to disconnect it? The ECU disengages the AC clutch under hard acceleration and some other situations.
When I just want to heat the windshield to maybe thaw out around the wipers so they won't tear when turned on. Or just simply to blow warm air up and over instead of through the vents w/o having the compressor run. Also maybe to help mileage on a long road trip when just needing a touch of defrosting that can be handled w/o the compressor. Or maybe I'm just a control freak ;)

FYI for anyone that's interested - the compressor/refrigeration system pulls moisture out of the air as it flows across the cold fins of the evaporator coil, that way the air is drier and can absorb more moisture as it flows up onto the windshield area (in a nutshell).
 

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marcat75 said:
Thanks for the tip!

When I just want to heat the windshield to maybe thaw out around the wipers so they won't tear when turned on. Or just simply to blow warm air up and over instead of through the vents w/o having the compressor run. Also maybe to help mileage on a long road trip when just needing a touch of defrosting that can be handled w/o the compressor. Or maybe I'm just a control freak ;)

FYI for anyone that's interested - the compressor/refrigeration system pulls moisture out of the air as it flows across the cold fins of the evaporator coil, that way the air is drier and can absorb more moisture as it flows up onto the windshield area (in a nutshell).
I hear ya on the control freak. I suppose if you found the exact wire in that harness where I circled in the picture you could wire a switch in to turn the compressor on and off. I would imagine it is just a ground applied to the circuit.
 

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akshunj said:
I hear ya on the control freak. I suppose if you found the exact wire in that harness where I circled in the picture you could wire a switch in to turn the compressor on and off. I would imagine it is just a ground applied to the circuit.
Don't even need a switch, just cut the right wire. If he wants the compressor to run he can just push the a/c button.
 

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marcat75 said:
Yes - I do really want to do that :) Have background in hvac, EPA refrigerant certified Univeral & Section 609, blah blah blah. Hence: "I know there's certain times it's beneficial to use but I think I'm capable of deciding that for myself" Also I've had no problems on previous vehicles that didn't have the compressor tied-in to the defrost switch because I knew when to use it. But yes I guess I'd agree that if someone doesn't know/can't remember to run the compressor every now and then they shouldn't disable it (hopefully they will have the need to run defrost).
IMO - I think the automakers were getting owners who didn't/wouldn't read the owners manual complaining that the defrost wasn't clearing the windshield so the automakers re-designed to accomodate for those people, kind of like idiot lights instead of guages.
If I had the wiring diagram I'd figure it out myself and post it, with a disclaimer of course for those that require that sort of thing.;)
Nothing personal, just didn't want others thinking I didn't really want to do it anymore and not post the answer if they have it.
There was a post somewhere, within the last couple of days, that included a link to a toyota service manual for a 2003 that has all the wiring diagrams.
 

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marcat75 said:
I'm hoping someone knows which wire I can "modify" to disable the a/c compressor from coming on automatically when defrost is selected and only come on when I push the button. I know there's certain times it's beneficial to use but I think I'm capable of deciding that for myself :confused:
I would love to be able to do this on my 2001 as well. Currently I have the belt cut off because the idler pulley is full of mud and was squealing like a stuck pig.

If you figure out which wire to cut, please let me know. I figure that I too am smart enough to figure out when I need the air conditioner to dry the air for me, once the belt is back on. In the mean time, I would like to not have it trying to switch on the A/C when it's not doing any good anyway.
 

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I did this on my '99, and if I remember right this is how I did it:
1. Take the frame and cover off the climate control panel.
2. There is a wiring plug that plugs into the dial that selects where the air comes out (so that whenever you turn to defrost it turns the compressor on).
3. Unplug and reassemble.

I live in the desert and I didn't need the air conditioned all the time, and I wanted the efficiency on long trips when I just needed a little air moving over the windshield. I can still just hit the A/C button when I have too much condensation.
 
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