ATC fan control? and WTF am I looking at?

Topic: ATC fan control? and WTF am I looking at? (Read 2684 times) previous topic - next topic

ATC fan control? and WTF am I looking at?

March 11, 2011, 11:21:25 PM

What controls the fan speed on a car with ATC? and where is this located.
I have an 88 Cougar XR7 and an 87 TC both with ATC. Both head units work in the TC neither work in the XR7. They will switch modes (defrost panel etc) in the XR7 but no fan. I found this gerry-rigged set up in the XR7 which the TC doesnt have (see pix). A small black box that says PWR Fan Motor with P/N F4LF19E624AA.
What Im trying to do is take the working system from the TC and put it into the XR7. SO if I can just figure out what controls the fan and where it is, I think Ill be all set.

ATC fan control? and WTF am I looking at?

Reply #1 – March 11, 2011, 11:22:54 PM

Oh when I said neither head unit works in the XR7 I mean neither works the fan.. The modes change

ATC fan control? and WTF am I looking at?

Reply #2 – March 12, 2011, 05:31:34 AM

The following picture is a typical A/C setup in a fox body vehicle.

The fan is controlled be the blower motor resistor. It's up behind the glove box IIRC.
The box in the pic you posted has a 1994 part number and I don't remember ANYTHING like that being back there....

ATC fan control? and WTF am I looking at?

Reply #3 – March 12, 2011, 01:30:44 PM

For eatc systems, there is a blower motor controller inside the hvac box.,,, which really sux.
Thanks for the pm on this, i did not realize cars with climate control have a different blower speed controller.

Me thinks i should scan this info and add it.

ATC fan control? and WTF am I looking at?

Reply #4 – March 12, 2011, 04:41:01 PM

yeah the TC was made in 2/87 and the XR7 12/87. The position of the actuators are different from each other. I found the TC's blower resistor and plugged it into the XR7....nothing with the fan. Also where the resistor was in the TC was a blank filler panel on the XR7. So Im guessing the controller is in the box like you said? Maybe those two wires that go up over the box and disappear???

ATC fan control? and WTF am I looking at?

Reply #5 – March 13, 2011, 02:20:13 PM

YO
good news
Blower motor controller is mounted to the outside of the duct work box.
The language used in the shop manual is misleading.

shop manual says to remove the three screws holding it on.
Just locate the connector with the wire colors per the evtm and extract the device.

there should be some simple parts on this board but basically it takes low current signals from the climate control and boosts these to high current so the blower motor can operate.

should be cake to get out.
The device you show on the left picture is the blower motor speed controller.
There should be an easy to replace power transistor (if its blown) or a resistor that is replaceable as well.
Im saying,,,these things can be repaired i would think.
It is critical that they are mounted correctly as well per the shop manual.
The device you have shown is also the same device mounted to the air box per the EVTM page 228.

ATC fan control? and WTF am I looking at?

Reply #6 – March 13, 2011, 02:25:10 PM

If you havent seen one yet,, trust me the blower motor resister bank will be obvious. ITs got a few wires coiled up and it looks like it should get hot,thats because it does.

the blower controller is different in that it steps up the current signals from the eatc and sends out the high current to the blower so the blower has enough power to operate.
Stands to reason that the electronic climate control "blower motor controller" has a big heat sync because it get hot as well.

you should be good to go,,if this is the fault.

ATC fan control? and WTF am I looking at?

Reply #7 – March 14, 2011, 11:46:33 PM

Yeah but I still have no fan. Did a check on the blower speed controller and theres power to it and at the (what I think is the resistor) but nothing heading out to the fan. Its a small rectangle mounted on the heat sink, with more power on one side than the other (test light gets way brighter on one side)

ATC blower control

Reply #8 – March 24, 2011, 11:07:49 PM

ATC system does not use a blower resistor. It has a fan controller that is just a power transistor controlled by the dash panel. The fan motor has 12V to the hot side and the ground side is controlled by the solid state fan controller. Even though this gives potentially infinite variability of the fan speed, the control head only provides low, medium and high options. If you ground the big wire at the controller the fan should run full speed. As I recall, the dash must be loosened and pulled partially back to remove the heat sink from the air box without damaging the glove box.