A/C Blowing cold at 60 degrees, but warm at 65?? Am I missing something here? lol

[biodole]

Ok guys, so I have a fairly new blower controller (the actual unit that sit inside the car with the controls for my a/c). I replaced it about 20,000 miles ago. My car currently has 88,000 miles and is in relatively good shape.

Anyway, I live in South FL - and the weather here has been getting pretty cool lately. It's about 40 degrees outside right now with a huge wind chill factor. Anyway, for about the last week (incidentally also the time it's been pretty cold out) my car a/c has been having a strange issue.

When I run the A/C at 60 degrees MAX a/c (coldest setting) the a/c blows nice and cold. However, when I ramp it up to 65 degrees, it starts blowing warm. At 68 degrees, the air coming out is outright hot...feels like I have the heater set to 85-90 degrees in the cabin.

Is something going on here?? Or am I missing something? Does this have something to do with the temperatures outside? I know it sounds weird that I'm using the a/c at all given the temperatures outside, however sometimes I prefer the a/c to riding down the highway with the windows cracked and unable to hear myself think lol.

Please give me some insight about this - I'm very confused and wondering if theres something wrong with my a/c - or if this is totally normal in cold weather.

thanks guys!

[FordNut]

See if this makes sense...

It should be trying to achieve the setpoint temperature in most circumstances. I know earlier EATC systems had a separate cabin air temperature sensor that it uses for a reference temperature. Not sure if the MM has a separate sensor or if it is now integrated with the EATC. If it is blowing out really hot air and you have it set for 65 degrees, maybe the sensor is bad.

MOST circumstances means all temperatures except the min and max. At the min 60 degree setting it should always run air conditioning. At the max (I think 90 degree) setting is should always run heat. Anything in between and it should automatically choose heat or air to achieve the setpoint temperature.

[fastblackmerc]

See if this makes sense...

It should be trying to achieve the setpoint temperature in most circumstances. I know earlier EATC systems had a separate cabin air temperature sensor that it uses for a reference temperature. Not sure if the MM has a separate sensor or if it is now integrated with the EATC. If it is blowing out really hot air and you have it set for 65 degrees, maybe the sensor is bad.

MOST circumstances means all temperatures except the min and max. At the min 60 degree setting it should always run air conditioning. At the max (I think 90 degree) setting is should always run heat. Anything in between and it should automatically choose heat or air to achieve the setpoint temperature.

I believe the sensor is behind the slots to the right of the EATC.

[RoyLPita]

Blend door actuator.

[biodole]

hmmm...

thanks for that info guys...

seems that my g/f's mercury montego is having the same issue.

I've already replaced the blend door actuator before. Maybe the sensor has an issue.

I will check out the senor and report back.

Thanks again

[musclemerc]

Mine is doing the exact same thing. Please post your results.

[TFB]

Mine was doing same when I bought it, found the sensor was unplugged from rear of EATC head...

Works fine now...

BTW the sensor is just behind the small grille openings just to the right of the EATC... Also if the sensor is the problem, it should give a code when the self test is performed...

[LincolnLSE]

im new to Marauders but not to MarkVIII's. Ive owned 2 Mark VIII's and I know that they suffer from the deadly blend door actuator, but I didnt know that Marauders had the same problem.

[fastblackmerc]

im new to Marauders but not to MarkVIII's. Ive owned 2 Mark VIII's and I know that they suffer from the deadly blend door actuator, but I didnt know that Marauders had the same problem.

Some Marauders have had the blend door problem, most haven't.

The two common problems are the o-rings inside the EATC need to be replaced and the BCM (Blower Control Module) needs to be either re soldered or replaced.

[RoyLPita]

I strongly believe that there is a tooth missing from one of the gears that are in the blend door actuator.

[2vmodular]

ye, it sounds like a blend door position problem. it could be caused by missing teeth on the blend door actuator. it could also be caused by an interior temperature sensor that is giving incorrect temperature values to the eatc control head.

for the first diagnostic step, run this test:

http://www.p71interceptor.com/eatcswap/selftest.html

and then report back here any codes that are displayed.

btw: lots of bacground info about how the eatc system in these cars works is avaliable here:

http://www.p71interceptor.com/eatcswap/


I strongly believe that there is a tooth missing from one of the gears that are in the blend door actuator.

[TFB]

IF it were the blend door why would it suddenly switch from cold to hot with one step in temp change??? Blend door problems usually cause the temp to never change...

[2vmodular]

60 degrees is a failsafe mode so that you can get cold air out of the vents if temperature sensors are broken. if you leave the engine running in your car with the eatc set at 60 degrees and the blower motor on high speed, you should be able to get the temperature of the car well under 60 degrees. playing around during 80 degree summer days, i've measured interior temperatures in the mid-30's with the eatc set @60.

at 60 degrees, the eatc control head ignores all temperature sensor data and commands the blend door actuator to move the blend door to the full cold position.

when you go up to 65 degrees, the eatc control starts looking at the temperature data again and commands the blend door actuator to position the blend door at what it thinks is the appropriate position to obtain the 65 degree desired interior temperature.

at this point, it is not definitively known why the blend door is in the improper position. like mentioned above, i'd run the eatc self diagnostics mentioned above as the first diagnostic step. this will command the blend door actuator to do a full sweep through it's travel range and monitor position feedback. if you've got chipped teeth on the actuator gears, you should see an error code. you should also see an error code if the blend door inside the plenum is stuck because of debris like a pencil in there. however, temperature sensors often will not set codes when they fail. and the venturi effect hose that goes to the interior temp sensor will not set an error code if it falls off either.

if all the above info seems too technical for you, it might be time to bring your car to the local ford dealership for repair. that greatly simplifies your repair, just describe your problem to the service advisor and you'll get a phone call when your car is fixed.


IF it were the blend door why would it suddenly switch from cold to hot with one step in temp change??? Blend door problems usually cause the temp to never change...

[TFB]

^^^^ AIN'T MY PROBLEM, fixed mine months ago by reconnecting the temp sensor that was unplugged... The code given indicated the circuit was open and with it unplugged that was no doubt the case...

BTW In 44+ years of owning vehicles, I ONLY visit the dealer for recalls, and sometimes not even then... Got the third letter for the cruse switch harness addition on my '93 Lightning a couple days ago... Since I never use it, it's been unplugged for a couple years now...

[2vmodular]

you did good fixing that problem. you figured out how to run the builtin eatc diagnostics and then how to physically access the faulty sensor wiring.

but one question that is still unresolved is how the temp sensor in your car got disconnected in the first place. these parts clip together with a great deal of force and don't just randomly fall apart.


^^^^ AIN'T MY PROBLEM, fixed mine months ago by reconnecting the temp sensor that was unplugged... The code given indicated the circuit was open and with it unplugged that was no doubt the case...

cars are becoming really complex electrically these days. if you need certain repairs done, the ford dealer is sometimes the only place in town that has the needed tools and training to complete the repair. either you only own older cars with simple electrical systems or you've been very lucky until this point in time.

btw: that cruise control recall involves placing a low amperage fuse inline with the deac switch on the master cylinder. unplugging the cruise servo does nothing to eliminate the reported fire risk.


BTW In 44+ years of owning vehicles, I ONLY visit the dealer for recalls, and sometimes not even then... Got the third letter for the cruse switch harness addition on my '93 Lightning a couple days ago... Since I never use it, it's been unplugged for a couple years now...

[TFB]

On the Lightning, I unplugged the switch on the brake junction block... Looked at that switch again today while I had it on the lift checking out a oil pan gasket leak, still dry with no sign of leakage... Gonna have to pull the pan and repl the gasket... Since I didn't have the lift avail except for the morning(at a buddy's car lot), I cleaned it and spread some RTV over the area, surprisingly it isn't leaking at the moment...

My Marauder had a tree fall on on back in '08 before I bought it, crunched the hood, busted the windshield and dented the top, I suspect the EATC head was removed at some point during the repair... I also found a long dead leaf behind the radio when I had it out freeing a stuck disc, guessing it got there at the same time...