A/C control switch in F355

ECU is in the front trunk. You have to remove the weather stripping and then remove the rear felt trunk liner. The ECU is located under the windshield cowling on the passenger side. It is buried and is yellow in color. The hose is on the left side of the evaporator box. Many of these pumps go bad and mine was letting some hot water in even when my switch said it was closed. By blocking the hose I have max cooling all the time. I guess the procedure to sync the system is turn off battery, disconnect the A/C ECU. turn on A/C switch, reconnect battery and ECU and then turn on ignition switch to on position and let system recycle. I have not tried this but everything else so will do it this weekend. If your car blows real cold air at max your pump is fine. On mine even with the A/C off I could feel warm air coming out of the vents so I knew mine was bad.

 

Yes Bob a defective valve(not pump) can do this........this is another issue with A/C systems that do not operate as they should.

 

Mine is working A OK
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Bob did the reset work.

 

I did the reset 3 times before I got the flapper door to work. I connected the barrel motor to the harness and let it hang so I could see it move. Before the reset it did not move at all. After the reset it turned and the reversed itself I am assuming back to the default position and it would not move again. Weird. A few years ago, I crimped off the heater hose going to the a/c water pump so the cold air can't be diluted with warm air. Which means I always have very cold air and even on 90 degree days, I only need the fan on setting 2. I have a spare ECU so I might give that a try.

 

So did anyone ever figure how to fix this issue?

 

There are multiple known reasons why the air blows only through the defrost vents. Many have already been listed.

1) by design (if the external air temperature is cold)... until the car warms up.
2) faulty "timing" actuator (usually stripped gears)
3) faulty actuator wiring
4) faulty ECU or specific chip in the ECU
5) faulty control panel (e.g. burned resistors)
6) jammed tambour... The foam rubber seals on the rotating barrel which diverts air to the screen can get a bit sticky. The rubbing leaves a layer of rubber and dust on the mating parts which can slow the movement. On my car, I can hear the actuator motor straining when it hits the sticky parts. I've tried to trim the seals, but access is insufficient to trim the entire width. The only option is to pull out the entire evaporator a$$embly. I've used a dry lube to lessen the strain on the actuator.

Resetting the battery will make the actuator cycle though its full range. Anecdotally, you'll need to warm up the car to get full functionality. This may or may not be due to a faulty outside temperature sensor under the driver's mirror.

The system can be interrogated with a Ferrari SD1 diagnostic tool. It may pinpoint the issue.