93 TC EATC Issue

My 93 TC has a problem relating to the EATC. Most of the time you have to put the blower control full on for the blower to work. I ran the diagnostics which returned no error codes. Occassionaly the unit works normally; most of the time it doesn't. I have heard a relay click under the dash in conjunction with the EATC. What am I missing? BTW I subscribe to the online Alldata.:banghead::banghead:

I doubt that relay click has anything to do with your blower problem.

Here's what I think is happening; there's a Blower Speed Control that regulates blower speed by restricting voltage to the blower motor. This is accomplished by running the power through a huge transistor mounted to the circuit board inside the blower speed controller.

Whoever made that board for Ford used a low melting point solder to hold the hot terminal to the board... we all know how hot these things can get... the solder melts and the transistor wont slow the blower anymore, hence; only high speed works.

The speed controller is mounted to the outside of the EATC unit, under the hood, behind the engine. It's hard to get at, it's directly behind the passenger side Valve Cover.

If you just re-solder the hot terminal to the board with some good solder, the problem should be fixed. Some folks just replace this controller too.

I don't have a photo.. hmmm.. let me see what's on the net.. BRB

Here's one picture from www.p71interceptor.com :
(the soldered hot terminal is on he flip side)

http://img88.imageshack.us/img88/9927/blowercontrollered9.th.jpg (http://img88.imageshack.us/img88/9927/blowercontrollered9.jpg)
( click to enlarge )

Thanks for the hint. Electronic troubleshooting isn't new to me, have been doing it for 40+ yeas, back when most electronic stuff glowed in the dark.

EATC blower problem: fixed. Removed blower control module and resoldered the base and emitter leads; checked the connector terminals it appears there was some corrosion on the terminals, so I cleaned them and reinstalled. Blower now functions normally.:grinyes:

Good job !! Did you have any trouble getting it in and out ?

Most of us can't get a tool on the inboard screw :(

Have to remember that one. Bought mine at the bone yard. I would have probably melted the sucker anyway Im not very good with the propane torch.

That side with the tough screw was broken by the guy before and is easy with the rest of it out of the way.

Question about that photo Towncar? That looks like a cut out switch on a furnace. (Round thing) Is that a safety switch for when the A/C coil freezes
or in case that thing really heats up?


WTG on a successful mission.

Thanks and Good Luck

...Is that a safety switch for when the A/C coil freezes or in case that thing really heats up?


That's a voltage regulation transistor. It gets really hot while it's slowing the blower, I believe that's one reason it's mounted inside the blower box.

Removing the controller wasn't that difficult once I removed the block to heater core hose. I didn't have any trouble with the mounting screws I just used a long 8mm 1/4 inch socket wrench. The round "thing" that goes inside is a TO-5 transistor mounted on a heat sink, this is what actually regulates the amount of current that is delivered to the blower motor. The EATC outputs a variable voltage that corresponds to the blower speed required this feeds the large transistor thus speeding up or slowing the blower speed. As the blower speed increases more current passes through the transistor thus generating heat, by mounting inside the air input housing the air flow helps keep the transistor cool.:2cents:

Thanks for info I figured it got hot when saw the heat sink and thought it was a safety in case it got too hot. Now I know.

Saw some rust too. That from condensation as that unit goes from hot to cold in the winter OR from moisture pulled into the system as it is removed from the inside of the vehicle.

Which brings me to the question I have been pondering.

When some one says rhe A/C is an evaporative system I always thought that
it meant that the Freon or R134A is changed from a liguid to a gas.
And that evaporation is what makes it do what it does.

Then I heard because it is an evaporative system that it will take moisture out of the vehicle.

only way I could see the system taking moisture out of vehicle is..

The floor door opens so air in is being drawn from car. Recirulatting.
I thought some of that air was passed through the heater core to dry the air
And then back to A/C side and into the vehicle.

Is my thinking somewhat right or am I missing some law of phyics here?

Thanks and Good Luck

Think of the dew point you see on the nightly weather, that is the temp were moisture in the air turns to water. This is dependent on the humidity of the air higher the humidity higher is the dew point. This water is what drains out the AC drip tube. The first AC systems were designed to lower the humidity in a wood factory so the wood would't swell. There are several tutorials on basic closed loop cooling systems available on line.

So it accumulates an then drips out the tube. i can remember a photo
pf the frame where it rotted out from the water. I couldnt understand why
water would lay long enough to rot it. I was thinking that with the moisture there is also an element of dirt also. Perhaps that dirt doesnt runout with the water, lays on the frame , accumulates and dams up the flow and once water passes all that left is wet mud.

I got enough trouble with salt here in Michigan eating it from the outside.
Last thing i want is it getting ate from the inside.

Thanks for taking the time to answer. Maybe if you field a few of these
treads Towncar will have more time to search the funnies. Trust me his
funny side is just as resourceful.

Thanks and Good Luck