white/purple wire in red HVAC plug.... - Ranger-Forums - The Ultimate Ford Ranger Resource


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  #1  
Old 07-07-2007
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white/purple wire in red HVAC plug....

anyone know what it is for? i am talking abou the white/purple wire that is in the red HVAC plug.......that is the only wire that i didn't use when i did my EATC swap and i think it has something to do with why my A/C isn't working.....

i have checked the purple wire from the EATC headunit to the safety switch and it is ohm'n out so i know there is no break in that wire......and the wire from the safety switch to the back of the compressor is all together......does anyone know were the green/white (i think that is the colors) goes to from the back of the compressor......it is in the same plug with the wire that comes over from the safety switch....
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Old 07-09-2007
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anyone........anyone at all
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Old 07-10-2007
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The white/purple is the "Hot in Run" wire in the truck's original HVAC wire connector. It should be connected to black/light green wire and to the red wire of the EATC head unit. The EATC will not work if the BK/LG does not have power.

[Note: According to John's How-to, If the EATC came from a 95~97 Explorer, it also has its own white/purple wire and that P/W should also be connected to three wires above.]
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Old 07-10-2007
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i will switch were the power wires go to (i presently have it tapped into the radio switched power).....could that be why the A/C isn't working; because the truck thinks the A/C is off?

the heat is starting to get to me when i drive this thing......

i checked the connections between the purple wire at the headunit and the purple wire at the safety switch on the dryer (under the hood), and it all ohm'd out fine......i am getting stuck here and burning up cause i don't have A/C when i want to drive the truck......now granted i don't drive it much, but when i do, i don't want to melt to leather seats...
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Old 07-10-2007
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could it be a bad EATC unit?
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Old 07-10-2007
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bob.....there is a 3 wire plug that came off my stock HVAC controls that i didn't do anything with when i installed my EATC.....the wire colors in it are: Green/Orange, Yellow/Green, Grey/Purple..........i know there is a Green/Orange wire that goes into the back of my compressor along with the wire that comes over from the safety switch (sorry can't remember the color)........

would that have anything to do with my EATC not allowing the A/C to function?
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Old 07-10-2007
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Quote:
Originally Posted by lifted97ranger
bob.....there is a 3 wire plug that came off my stock HVAC controls that i didn't do anything with when i installed my EATC.....the wire colors in it are: Green/Orange, Yellow/Green, Grey/Purple
Those control the stock 97 blend door. You don't need them because you ran new wires from the EATC HU to the EATC blend door actuator.
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Old 07-11-2007
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what about that white/purple wire, could because i didn't use it for the power be the reason the A/C isn't working?
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Old 07-11-2007
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Quote:
Originally Posted by lifted97ranger
what about that white/purple wire, could because i didn't use it for the power be the reason the A/C isn't working?
If you have the EATC hooked up correctly to a different "Hot in Run" wire like you said, it shouldn't make any difference.
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Old 07-11-2007
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Quote:
Originally Posted by rwenzing
If you have the EATC hooked up correctly to a different "Hot in Run" wire like you said, it shouldn't make any difference.
well darn.....i got it hooked into the stereo switched+......dang i have checked and rechecked ALL the wiring and i don't see a problem........

should there be voltage on the purple wire when the EATC has the A/C on? maybe that is it......if it does have voltage, then by chance do you know how much it is?
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Old 07-11-2007
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The purple wire should be hot (roughly battery voltage) when the EATC wants the A/C to run.

~~~~~~~~~~~~~~~~~~~~~~~~~

Just noticed something....

I know that John's how-to says that the 95~2000 Rangers all use the same wiring method for the EATC. I might be missing something but it looks like the Ranger wiring for 95~97 is significantly different from 98~2000.

The 98~00 uses the purple wire only to signal the PCM when A/C is desired. Using other inputs, the PCM then makes the final decision when to activate a relay to switch on the compressor clutch. (This is similar to how the factory Explorer operates.)

For 95~97 Rangers, the purple wire actually carries the full current for the A/C compressor clutch directly, meaning that you would be switching several amps directly through the EATC HU. Obviously, the stock 97 HVAC mechanical mode switch is designed to handle this level of current but I question whether the same is true of the solid state switching in the EATC HU.
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Old 07-11-2007
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so do you have any ideas on how to fix the problem? i would say it is the EATC HU not sending enough power through the purple wire.......

could i add a switched 12v source to the purple wire for when i want A/C operation? then let the EATC in auto mode decide how much air to blow out?
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Old 07-11-2007
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Quote:
Originally Posted by lifted97ranger
so do you have any ideas on how to fix the problem? i would say it is the EATC HU not sending enough power through the purple wire.......

could i add a switched 12v source to the purple wire for when i want A/C operation? then let the EATC in auto mode decide how much air to blow out?
I'd like to get John's take on whether the EATC HU is capable of handling the current for the compressor clutch directly. My gut says it can't but I have no testing or anything else to back that up. Besides yourself, has anyone actually ever done the EATC on a 95~97 Ranger?

Check and see if you're getting anything like B+ on the purple wire when A/C is selected on the HU. If so, then my theory is wrong.
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Old 07-11-2007
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Quote:
Originally Posted by rwenzing
I'd like to get John's take on whether the EATC HU is capable of handling the current for the compressor clutch directly. My gut says it can't but I have no testing or anything else to back that up. Besides yourself, has anyone actually ever done the EATC on a 95~97 Ranger?

Check and see if you're getting anything like B+ on the purple wire when A/C is selected on the HU. If so, then my theory is wrong.
i don't know of anyone else who has done the EATC on a '95-'97 Ranger....

if the EATC HU was capable of handling it, then how would it be wired for it to handle it?

this might sound stupid, but what is B+? and how do i check for it?
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Old 07-11-2007
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Quote:
Originally Posted by lifted97ranger
i don't know of anyone else who has done the EATC on a '95-'97 Ranger....

if the EATC HU was capable of handling it, then how would it be wired for it to handle it?

this might sound stupid, but what is B+? and how do i check for it?
Sorry, B+ is battery positive voltage. You should see something like 10~14 volts on the purple when the engine is running, the interior temp is higher than the EATC display temp and the A/C button is pushed.

If it does turn out that the HU cannot handle it, you could do a minor wiring revision and add a relay. Of course, you'd probably need a replacement HU, too - if I'm right.
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Old 07-11-2007
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Quote:
Originally Posted by rwenzing
Sorry, B+ is battery positive voltage. You should see something like 10~14 volts on the purple when the engine is running, the interior temp is higher than the EATC display temp and the A/C button is pushed.

If it does turn out that the HU cannot handle it, you could do a minor wiring revision and add a relay. Of course, you'd probably need a replacement HU, too - if I'm right.
alright i will test the purple wire when i get home from work.......oooo the interior temp is MUCH higher than the temp on the EATC (been runnin high 90's here lately....EATC set on 60*)

would i need a replacement EATC HU before trying the minor wiring revisions with a relay or do you want to try putting the 12v to the purple wire through the EATC HU first?

why don't we try the minor wiring revisions first that way i don't have to buy and wait for another EATC HU off eBay.....

is there any way you can draw me up a diagram for the new wiring with the relay and i will try it tonight?
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Quote:
Originally Posted by lifted97ranger
why don't we try the minor wiring revisions first that way i don't have to buy and wait for another EATC HU off eBay.....

is there any way you can draw me up a diagram for the new wiring with the relay and i will try it tonight?
We don't know if the HU is smoked yet or if it will or won't handle the amperage. Better check the purple wire first.
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Old 07-11-2007
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so no matter what, the HU has to supply a voltage to the purple wire? even if it is a low volt/amp amount through the purple wire?
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Old 07-11-2007
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Quote:
Originally Posted by lifted97ranger
so no matter what, the HU has to supply a voltage to the purple wire? even if it is a low volt/amp amount through the purple wire?
The EATC HU is the switch that allows power to pass from the Hot-in-Run wire to the purple wire. Your 97 uses that wire to power the compressor clutch directly instead of using a relay as on later years.

My thought is that several amps being drawn by the compressor clutch could fry the switching circuit in the HU.
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Old 07-11-2007
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Quote:
Originally Posted by rwenzing
The EATC HU is the switch that allows power to pass from the Hot-in-Run wire to the purple wire. Your 97 uses that wire to power the compressor clutch directly instead of using a relay as on later years.

My thought is that several amps being drawn by the compressor clutch could fry the switching circuit in the HU.
alright i will check to see if the purple wire is getting voltage when i get home from work....

now i know when i select the A/C option on the HU, it turns my efan on, so that means it is getting power across the purple wire correct?

if it isn't getting voltage, then do i need a new HU? and if it is, but little voltage, then what could be the problem? possible a cooked HU?
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Quote:
Originally Posted by lifted97ranger
alright i will check to see if the purple wire is getting voltage when i get home from work....

now i know when i select the A/C option on the HU, it turns my efan on, so that means it is getting power across the purple wire correct?

if it isn't getting voltage, then do i need a new HU? and if it is, but little voltage, then what could be the problem? possible a cooked HU?
I suspect that it will either have voltage or have none, nothing in between.

I don't know about the efan because I don't know how it's wired.
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Old 07-11-2007
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Quote:
Originally Posted by rwenzing
I suspect that it will either have voltage or have none, nothing in between.

I don't know about the efan because I don't know how it's wired.
the efan is tapped into the purple wire behind the dash....
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Quote:
Originally Posted by lifted97ranger
the efan is tapped into the purple wire behind the dash....
Then I agree that the purple wire must be getting voltage.
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Old 07-11-2007
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does the purple wire go straight from the HU to the A/C safety switch? or does it go somewhere else before the safety switch?
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Old 07-11-2007
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i am about to rip the dang thing out and go back to my stock setup....

i will take some pictures of the wires that i have together from the stock harness and the EATC harness when i get home....so you can see if i have a screwed up wiring....
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