355 heater temperature valve problems. Help! | FerrariChat

355 heater temperature valve problems. Help!

Discussion in '348/355' started by Slickmk1, Feb 7, 2016.

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  1. Slickmk1

    Slickmk1 Karting

    Jul 22, 2014
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    Mark
    #1 Slickmk1, Feb 7, 2016
    Last edited by a moderator: Sep 7, 2017
    Hi guys,

    In desperado need of some help re my 95 berlinetta. I have attached some pics and hope others may have experienced this problem before to guide me in what and how to test. My heater control valve was not moving and I had seen that this is a common problem for a few reasons.
    I know the valve works fine as I can disconnect it from the motor and turn it by hand. The temperature then regulates between hot and cold with no bother. I there for assumed that the motor was duff so I got a new one. Swapped it over, plugged it in and nothing. Even if not connected it doesn't turn.

    So, the fan works fine, the ac works fine and the direction also. Just the temp control not working.

    I have dismantled the hvac unit ready to test. I know I can test on the motor connection side of the loom and is that an ecu and relays for the heating that I have pictured below?

    Shooting in the dark here guys so all and any help welcome.

    Also I could only see the one fuse in the foot well for the system. Am I missing anything there?

    Thanks guys,

    Mark
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  2. Slickmk1

    Slickmk1 Karting

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    #2 Slickmk1, Feb 7, 2016
    Last edited by a moderator: Sep 7, 2017
  3. Slickmk1

    Slickmk1 Karting

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    #3 Slickmk1, Feb 7, 2016
    Last edited by a moderator: Sep 7, 2017
  4. Slickmk1

    Slickmk1 Karting

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    #4 Slickmk1, Feb 7, 2016
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  5. johnk...

    johnk... F1 World Champ
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    That is the ABS ECU pictured. The AC ECU is back up under the dash behind the bank of relays shown in the picture.
     
  6. LorenzoR

    LorenzoR F1 Rookie
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    I just developed the same issue. Ive tested everything. I even have 3 hvacs that I tried. Everything works including that little motor you just bought. Ive come to the conclusion its the ac ecu cuz something isn't sending a signal to that little motor to open and close. There is supposedly a reset procedure for it but I ve tried it several times but it didn't work
     
  7. johnk...

    johnk... F1 World Champ
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    Also, you can test the motor by disconnecting the plug and apply +/- 12 V across the pins where the yellow/black and red/white wires were connected. + volts moves the valve one way, - volts the other. I believe they are the outer pins in the receptacle on the valve housing. DO NOT connect any power to the plug on the end of the harness.

    If the valve moves when you do this it means that you are not getting power from the ECU.
     
  8. bcwawright

    bcwawright F1 Veteran

    Jul 8, 2006
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    #8 bcwawright, Feb 7, 2016
    Last edited: Feb 7, 2016
    Here are some "Sensors" that may need to be part of the diagnostic checklist:


    1. Outside Air Temperature Sensor located on the Driver Side Rear View Mirror

    2. Cooled/Heated Air Temperature Sensor(also known as Treated Air Sensor)...

    3. Evaporator Temperature Sensor

    4. Passenger Compartment Sensor(Very Important as this Sensor is used to compare with the control unit knob setting on dashboard which in turn variate s the heater valve stepper motor)


    If any of these are not working the microprocessor(ecu) cannot compute logic(one of its many functions is to control the stepper motor on the heater valve)...
     
  9. LorenzoR

    LorenzoR F1 Rookie
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    Do you know how to test these sensors.
     
    dbluestein likes this.
  10. bcwawright

    bcwawright F1 Veteran

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    Anyone who is knowledgeable about "Negative Temperature Coefficient Thermistors", and has the equipment can test these.

    I believe all of these are the NTC type but someone else may want to comment

    Maybe JohnK can help out
     
  11. cf355

    cf355 F1 Rookie

    Feb 28, 2005
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    chris

    I'm currently looking at a friend's 355 and the heating/ac works properly including the stepper motor however when turned on the stepper motor closes the flap. Take the stepper motor off and reset it again to full open, it closes the flap once plugged in and turned on. Am going to to take a look at the sensors next as it appears one has failed.
     
  12. johnk...

    johnk... F1 World Champ
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    If they are NTC or PTC they should have 2 wires. To test you would just measure the resistance between the two wires and check if it varies if you heat the sensor up, say with hot air from a hair dryer. That would at least show they were responding, but without know the rated resistance (for example they come in 100 ohm, 1000 ohm, etc) it's hard to say they are ok. But chances are, if the resistance is changing smoothly with heat and cooling, it's ok.

    By the way, I'm following this thread closely because I have the same issue. When out for a drive on a cool day and heat was working fine. Next time out it was warmer and I could not shut the heat off. Checked the valve and it was working fine. I applied a voltage to close it and everything works: AC, air direction, Fan speed, temp selection (as long as cooling is required) but heater valve will not open even if I set the controls to manual and the temp selector to max heat (red dot). I setup a little circuit to tell me if power was being sent to the valve and wither it was being asked to open or close. No power either way. No signal from the AC ECU. Being winter now, I' not playing with it and come spring I think I may just have a diagnostic run on it unless something come of this thread.

    Would love to have an AC ECU to swap though.
     
  13. johnk...

    johnk... F1 World Champ
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    Different problem. If you are talking about the recirculation vent flap, if the button is not depressed it is supposed to open and close based on time and/or outside/inside temperature. If the button is depressed it will close. This is discussed on the owners manual.
     
  14. bcwawright

    bcwawright F1 Veteran

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    Ok,the WorkShop Manual Volume 3-Section "Air Conditioning" is saying they are "NTC" type.

    I agree that the big issue in testing is what values are considered "within limits", according to the logic program in the ECU.
     
  15. cf355

    cf355 F1 Rookie

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    Yes I'm aware of what the manual says.
    Whats happening here is the flap is closing and never opening despite any of the settings.

    When the stepper motor is removed and manually reset (12 volts)to open position and then reinstalled (with flap open).....car is started & the flap closes (regardless of where the settings are ) and never opens again although the ac , defogger and heating are working perfectly.
     
  16. Slickmk1

    Slickmk1 Karting

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    This is all great guys.
     
  17. Slickmk1

    Slickmk1 Karting

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    This is awesome. Never realised there would be so many sensors as possible problems.

    Obviously the first one is in the mirror. Where am I looking specifically for the others?

    Thanks,

    Mark
     
  18. bcwawright

    bcwawright F1 Veteran

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    #18 bcwawright, Feb 7, 2016
    Last edited by a moderator: Sep 7, 2017
    #8 and #13 in Diagram

    Cabin Sensor is circled in yellow in pic
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  19. LorenzoR

    LorenzoR F1 Rookie
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    Chris ive done all that. The only things I haven't checked is the sensors that bruce has mentioned. im going to try to test them as well. keep us posted please
     
  20. Slickmk1

    Slickmk1 Karting

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    Thanks Bruce.

    Just out of interest is the heater ecu the box marked 46 in that pic? Is that in the car cabin some where or the other side of the fire wall in the trunk?

    The only reason I ask is my friend has a 355 and said I can try his so it's also got to be worth a go.

    Thanks,
     
  21. johnk...

    johnk... F1 World Champ
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    Not Bruce, but yes, 46 is the AC ECU. As I said, it is mounted behind the line of relays which was along side the ABS ECU shown in your earlier post. Under the windshield area.
     
  22. drbob101

    drbob101 F1 Rookie
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    This is timely for me as of this weekend. Took my 98 Landcruiser to a place to have a remote starter installed. Picked up the truck and when heater controls were set to auto the fan blew at full speed regardless of the temp dial setting. It would switch from heat to Ac and change the ducts but the fan was on high all the time. If I took it off of auto I could control it manually.

    Went back to the shop and explained it to the owner and asked if he had any ideas. He said right away, yes. He came out and said the passenger sensor was unplugged and he had plugged it back in. He unplugged it and all is well. He said the sensors sometimes get clogged and people unplug them although I never did but my point is in this case that plugging the sensor in made things whacky.

    So to Bruce's point , maybe it's a sensor issue.
     
  23. Slickmk1

    Slickmk1 Karting

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    Yeah, need to check all these. Thanks for all the help guys. It's cold in the uk now and a pain to not be able to adjust the temp inside the car.
     
  24. johnk...

    johnk... F1 World Champ
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    Me about it. Snowing again today in New England. 23* F. Fortunately, I have a spider and don't driver it in winter.
     
  25. m.stojanovic

    m.stojanovic F1 Rookie
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    #25 m.stojanovic, Feb 8, 2016
    Last edited by a moderator: Sep 7, 2017
    Here are the values of the four sensors in the 348, should be similar in the case of 355.
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