355 heater control valve

Lots of advice on the FChat forums, jstar...

http://www.ferrarichat.com/forum/threads/355-heater-problem.134274/

Substitute valves may be sourced from SAAB and VW (but some need to be modified to fit)

Could be the microchip in the ECU in the forward luggage compartment (not the control panel).

http://www.ferrarichat.com/forum/threads/f355-hvac-ecu.526186/page-2#post-145236285

You may need to apply power directly to the valve to prove the valve is faulty.

Pins 1 and 5 on the valve electrical plug control the motor. Reverse the polarity to change the direction of the motor. There is a position feedback circuit in the valve which may have to be checked also.

Cooling Circuit

Cheers.
Ian

 

What Ian said. ^

Sometimes it's the valve, sometimes it's the HVAC ECU (not the control panel).

 

The valve can be sourced easily as others have said (I think I bought mine on Amazon for under $10), however the motor is becoming increasingly difficult to find.
I have a spare which I bought since mine wasn't working. Put the new (used) one in and had the same issue. Did a bench test with 12v and found both motors to be functional. Sent my HVAC ECU out for repair to ASI (like several other F-chatters), but continue to have the same issue. I'll post up when I have time to dig into it further.
Best of luck!

 

does anybody know where the grounds are for that valve, the diverter motor? I have two working ECU's and those two motors still don't work. They work on the bench but wondering if there is a bad common ground for those two motors? I have the electrical printout but does not show where the grounds are located? Under dash, trunk area?

 

There are no grounds per say. The HVAC ECU provides power to the motor via the 1 and 5 positions on the connector to the motor. It switches between pin 1 = 12V and pin 5 = G and pin 1 = G and pin 5 = 12V depending on which way it needs to move the valve to give the correct air temp. Problem could be elsewhere, like a temperature sensor. Best to have it properly diagnosed with SD I or SD II .

 

So the pins on the end are the power pins? Since I found it quite challenging to find the stepper motor when I had originally replaced it a few years ago (to get my system to work properly again), I have been purchasing them when I see them come up for sale. I now actually have a spare "944" motor and three "917" motors... wondering if I can just switch the end leads to get it to work like the "944" for our cars?

If anyone wants a perfectly running "917" motor, I'm now in a position where I don't mind letting one or two go for around $100/obo+shipping.

 

Yes, the end pins are power to the motor. The +/- is swapped on them by the AC ECU to get the motor run CW or CCW (open-close). It is an ordinary motor (not stepper type) and it's rotation and positioning of the water valve (closed, partially open, fully open) is controlled by the in-built potentiometer (the 3 middle pins) which signals to the ECU what the angle of rotation of the water valve is.

 

Miro - is it correct then that the power to the motor is turned off based on the pot. "reading?" As an aside, I was always wondering if the little motor/gearbox for the cabin re-circulation air flap stays energized once the flap reaches max. travel or if the power is shut off by reading the stall current or turned off based on a time-out. Any idea?

 

Not possitive who it was but I remember some years ago another took the flap motor apart and I believe it had a similar pot reading system but a bit of a guess. Maybe bruce wright, i tried a search to no avail. They took it apart so it was a good photo of how it worked.

 

Yes, the heater valve motor is stopped when it reaches the desired position (resistance of the pot), as controlled by the AC ECU based on the selected temperature and the input from the temp sensor. The air direction motor is operated in a similar manner.

The re-circulation motor is just stalled and it stays stalled (!?). Bad design causing breaking of the gears and/or the flap shaft. I have installed limit switches for fully open and fully closed to cut power to the motor.

Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login

 

So it just stays stalled then??

 

You dont happen to have a cut apart one or found a pic of one. My original one was not working likely 8 years ago but i just bough a new one. I thought I saw a pic of a cut apart but obviously it does not work the way I remembered.

 

Motor / Gearbox internals

Image Unavailable, Please Login

 

Imput from which temp sensor ? Outside? Cabin?

 

Thanks Miro. I should have known you've already done something like this External micro switches for the flap assembly are in my future. Or perhaps just a timer circuit would be fine - set on "the high side." So maybe the motor stays energized 5 seconds longer than needed rather than constantly energized whenever the ignition is on/car is running. That would not be so horrific as compared to the original design.

 

It would be based on the cabin temperature sensor but the ECU probably takes into account the outside temp. sensor reading also, to some extent. That's how a "proper" climate control system would function, anyway.

 

It should be the cabin sensor. The AC ECU will, I believe, open the valve more if the cabin temp is lower than the selected temp and, as the cabin temp reaches the selected temp, the ECU will start closing the valve until equilibrium is achieved.

 

I have two working ECUs and both don't trigger the air diverter or water temp valve to work. It always defaults to defrost. I know the outside temp works-- bench tested it, so maybe I have a bad cabin sensor. Does the lower dash need to come out to get to it?
I can't really get my hand behind the dash to get to the sensor.

 

I am pretty sure if you taske the dash gauge pod off and then the lhs air vent its rght there. Had mine off last spring tomget vents done by Dave.
Someone who has had their vents done recently could confirm.

 

I have used other timers but never a 12 volt but I would think they make one. Would be a nice upgrade

 

You would probably need two timers as the polarity on the motor is swapped for closing/opening. Also, with timers, you would still have the high stress on the gears and the flap shaft for those few seconds which, being repetitive, could still cause damage. With limit switches, you can adjust them to cut the power to the motor just before the stall so there will be small stress but still enough pressure on the flap to keep it closed.

 

Does anyone know how much current it actually draws while working?

 

I think you are right. That should give access to the sensor. Thanks

 

If I remember well, when I tested my new fresh air flap motor in free run, it was about 0.1 to 0.15 amps. Of course, at high loading or stall, this would shoot up to 3-5 times this value.