"Hot wiring" the 348 heater valve? | FerrariChat

"Hot wiring" the 348 heater valve?

Discussion in '348/355' started by ///Mike, Jun 18, 2018.

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  1. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
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    Could have sworn there was a thread on here describing the electrical characteristics of the 348 heater valve but it didn't turn up in a search, so here goes...

    Trying flush my cooling system. Never had any trouble with the heater valve in the past and, in fact, it worked just fine for the first round of flushing. But no matter what I tried I couldn't get heat out of the vents during the second flush, even though the hose heading to the heater valve was warm. Had both the temp and fan control set to high but the only thing coming out of the vents was ambient air.

    During the first round of flush I noticed that the heater temp had to be set to max in order to get heat so it's my guess that the control unit will not activate the heater valve above a certain ambient temp. Can anyone confirm or deny that?

    In any case, I'd like to find a way of either tricking the climate control into actuating the valve, or just to hotwire the valve temporarily in order to properly bleed the cooling system. Problem is, I have no idea what voltage to apply to the valve, or even if the voltage is constant when the valve is supposed to be fully open.

    So, any suggestions as to how to either manually open the heater valve or play some electrical trickery to get it to open? Surely there's got to be a way to do it in order to bleed the cooling system in hot weather.
     
  2. m.stojanovic

    m.stojanovic F1 Rookie
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    You can operate the valve with a 12V supply on the end pins in the 5-pin socket on the motor. One +/- orientation opens it, the opposite closes it. Since in such manual operation there will be no control when to stop the motor, you have to watch the movement of the connecting bar between motor and valve, or the tab at the valve body, towards their stops and disconnect when they are near the stop. The attached pics show the position of the bar and the tab when the valve is CLOSED. So, to open the valve, they will need to be moved towards their other stops. Briefly touch the end pins with 12V and see which way the bar is moving to find the power supply polarity which will move it to near the "open" stop (the bar is moving rather slowly so you will have time to react before it hits its stop). Avoid hitting the stops with the bar as it will stall the motor and stress the gears inside.

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  3. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
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    Hugely helpful, Miro. Once again, I am in your debt. I was afraid that the climate control unit might be doing something strange to control the valve, or at the very least running the motor off of 5 volts. Considering the rarity of 348 climate control bits I don't want take any chances. Think I'll use a regulated 12 volt bench supply to power the motor so I can use the on/off switch to control movement whilst keeping a close eye on the movement.

    Out of curiosity, am I correct in assuming that the purpose of the potentiometer within the assembly to provide position information to the climate control unit in order to prevent loading the motor/gears against the stops?

    Finally, in searching for info on this topic I found reference to parts from other applications that would interchange directly with the Ferrari bits, but subsequent posts suggested that these were NLA. Is anyone aware of currently available rebuild parts for the 348 heater valve?

    Again, Miroljub, many thanks for your help. I'm getting very close to getting the car back down on the ground after many months but not being able to properly bleed the cooling system could have turned into a real impediment if it weren't for your kind assistance.
     
  4. innerloop

    innerloop Formula Junior

    Jan 17, 2010
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    Houston Heights, TX
    Could someone who knows give us some information on the specific pins in the connector? Specifically which two pins are for the motor and which pins are for the potentiometer reading? Thanks.
     
  5. m.stojanovic

    m.stojanovic F1 Rookie
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    You are absolutely correct. Absence of a potentiometer in the fresh air flap motor is what brakes its gears or the flap coupling.
     
  6. m.stojanovic

    m.stojanovic F1 Rookie
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    The information on the position of the valve is not only to prevent overloading of the motor against the stops but it is also for the AC ECU to be able to set the percentage of opening of the valve in order to achieve the demanded temperature, taking into account the outside air temperature, inlet air temperature atc.
     
  7. Qavion

    Qavion F1 World Champ
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    #7 Qavion, Jun 18, 2018
    Last edited: Jun 18, 2018
    Innerloop, pin numbers are not shown in the diagrams, so you'll have to go by wire colours (assuming the colours are visible). They are as follows:

    Red-blue and yellow-black are the motor wires (polarity changes depending on whether the valve is opening or closing). Pin numbers may possibly be 1 & 5 or 1 and 6.


    The remaining three wires are the potentiometer (black = earth, possibly pin 2, blue wiper arm (pin 3?), yellow (power from ECU/Control Panel) (pin 4?)

    Anyway, here's the diagram: (See "Water Heating Valve Control Motor")

    F348 HVAC Wiring Diagram

    (Edit: disregard.. I see Miro has already answered the question in another thread: Heat won’t turn off
     
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  8. Qavion

    Qavion F1 World Champ
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    What part of the valve were you looking for, Mike? I bought a VW combi valve ("cock") a few years ago which can be modified to suit the valve portion (not the motor/potentiometer part). See link below

    F355 heater/ac control ecu
     
  9. m.stojanovic

    m.stojanovic F1 Rookie
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    On my (unmodified, I believe) heater valve, the valve body has a Volkswagen "W" stamp and it can be seen that part of the plastic has been cut-off in order to mate the valve with the motor bracket. There is a sticker on the valve with number 26079011 but this is neither Ferrari nor Volkswagen part number.

    Anyhow, the valve is Volkswagen p/n 171819809E and it is easily available. Its plastic extension is cut as shown on the pictures and the tang needs to be cut a bit shorter, bent upwards and a hole drilled through it. Looks like that's how it was originally done for Ferraris.

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  10. m.stojanovic

    m.stojanovic F1 Rookie
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  11. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
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    Thanks for the additional info, gentlemen. The potentiometer serving two purposes makes perfect sense.

    As for parts availability, I was wondering what's available and what's not, so I know what parts to keep an out out for. It appears the motor itself is NLA from either Bosch or Saab, which is not exactly encouraging. :(
     
  12. m.stojanovic

    m.stojanovic F1 Rookie
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    There is a possible replacement valve sold by Summit Racing (https://www.summitracing.com/int/parts/vta-50507-vua/overview/, $89.99). I can see that the valve actuator has 5 wires, looks like 2 for the motor and 3 for the potentiometer. If the 3 wires are for the potentiometer, and its resistance is similar to the Ferrari one (5.5 Kohm), the valve can be connected to the Ferrari's 5-wire loom. Otherwise, it can be installed complete with its controller and manually operated (nice control knob). Perhaps worth buying and checking it out.

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  13. ///Mike

    ///Mike F1 Veteran

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    Fortunately, my climate control seems to be fine at present. But the scarcity of certain parts concerns me for the future. That these electric heater valves exist is encouraging because even if its not totally compatible out of the box one has to think that a skilled EE could find a way to control it with the 348's ECU.

    Thanks for sharing that info, Miroljub. I wasn't aware these existed.
     
  14. ///Mike

    ///Mike F1 Veteran

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    Nice find! Wonder what it'd take to use it with the factory CCECU.
     
  15. m.stojanovic

    m.stojanovic F1 Rookie
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    If its potentiometer is around 5 Kohm, then it can be connected straight to the Ferrari's 5 wires. In such a case, the only thing to find out would be in which orientation the two potentiometer end wires (wires 2 & 4 of the Ferrari's connector) go to the aftermarket actuator's two pot end wires (the wires between which the resistance does not change with the valve rotation). If the orientation is incorrect, you would get more heat when you set to less heat and vice versa. Then you just simply swap the two connections.
     
  16. m.stojanovic

    m.stojanovic F1 Rookie
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    If the potentiometer of the aftermarket unit has different resistance (like 3 Kohm or 10 Kohm), it will not work. Perhaps certain logic interface which would convert the range 0-3 Kohm, or 0-10 Kohm, to 0-5 Kohm could be a solution. Or it would probably be a voltage logic converter (Operational Amplifier) that would do volts conversion, not actually the resistance conversion.
     
  17. m.stojanovic

    m.stojanovic F1 Rookie
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    On second thoughts, if the AC ECU controls the valve based on voltage (coming from the potentiometer's wiper, the middle pin), then it shouldn't matter if the potentiometer in the aftermarket valve is somewhat different. If it is (say) 10 Kohm, the voltage on its wiper, for a given position of the valve, will be the same as on the original Ferrari's 5.5 Kohm pot so it should work. What the AC ECU does is, I think, it calculates the voltage that it wants to see from the potentiometer's wiper according to the selected temperature and other relevant sensors inputs and it then moves the valve until it gets that voltage from the potentiometer.
     
  18. whyte

    whyte Formula Junior

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    ...

    Mother of God. That is a MAGNIFICENT diagram! Whoever cleaned that up, you are a true VIP.
     
  19. Qavion

    Qavion F1 World Champ
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    LOL... Thanks.. Yes, it does clean up well... but lots of "elbow grease" required.

    These diagrams are constantly evolving. It's easy to add notes to the diagrams with Windows Paint (or something similar). However, I'm relying on my fellow FChatters to proof read them, though... I don't have a 348 to double check the wiring.

    Other diagams available on request :)
     
  20. Cauf61

    Cauf61 Formula Junior

    Jul 12, 2016
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    Indeed. Anything between 3.3 k and 10k will do fine.

    Like explained in the ECU topic, the ECU compares the voltage from the potentiometer to a D/A conversion from a stored table ( temp/voltage) and regulates to achieve balance via the heater valve. Mostly done by an few opamps followed by an power transistor.
     
  21. chas-3

    chas-3 Formula 3
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    This post just saved me from a lot of searching. Valve came in today, just under $11.00. Cheapest Ferrari part EVER?!
     
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