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Struggling with Heater Valve / Heater Control Testing. Super stumped.

Discussion in 'Mondial' started by Albert Penello, Mar 10, 2020.

  1. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    The problem I'm having is the Heater pot seems to have no effect on the heater valve. I've been doing a lot of reading on the issue and I'm absolutely stumped. This thread was a good read, I've gone over everything and am unable to get the pot to work. My fans work, and the fan pot works and I can get a range of blower speeds.

    Heater works, as I have the heater valve connector disconnected letting heat pass (it's cold here in Seattle)

    Here's what I've done.

    1. Removed heater valve and inspected the physical heater valve plunger and it's in good shape. As said above heater and blower works fine.
    2. Checked all relays and fuses, specifically the three relays under the dash at the back of the center console.
    3. Put an OHM meter across the heater pot terminals, and verified 0-10 OHMs as the pot moves.

    What I was told to do was wire in a light across the terminals at the heater valve. Turn on the car and press the push-button unit to any position and turn the heater pot. The light should blink and eventually go off.

    So here is where I'm stumped - no matter what I do, I cannot get any movement on the light. It's always full 12v.

    1. If I remove the SIPEA 0440 relay under the dash, the light stays on (!)
    2. If I remove the interior temp sensor wiring, the lights stays on
    2a - I grounded out the pink wire on the temp sensor and the light goes off.
    3. If I remove the 4-pin plug at the HVAC ECU, the light goes off.

    So no matter what I do, I cannot get the heater pot to change the light. However, everything else seems to be in working order.

    The thing that seems very strange to me is that removing the heater valve relay keeps the light on. According to the wiring diagram that should shut it off.

    Am I doing something wrong?

    @afterburner I'm hoping you can take a look and provide some advice!

    https://www.ferrarichat.com/forum/threads/a-c-electrical-testing-advice.562449/
     
  2. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
    Uk
    Are you sure you have the correct relay fitted. One relay can be normally open, other can be normally closed if i remember my electrics correctly. Try changing for another on the board to see if it cures the problem
     
  3. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Jan 11, 2001
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    What year/version Mondial? (Your Profile only lists a 360.)
     
  4. Wade

    Wade Two Time F1 World Champ
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    Mar 31, 2006
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    What lingo is that? Heater Pot and Fan Pot?
     
  5. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
    Uk
    I think his fan pot is number 61 on the drawing, listed as air conditioning fan speed variator and his heater pot is number 64, air con potentiometer for temp selection . Everything seems to end up at number 109h, electronic unit for internal temp ( under passenger footrest) if that helps
     
    Wade likes this.
  6. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    "Pot" would be another way to talk about a potentiometer (http://www.resistorguide.com/potentiometer/) in reference to the heater knob on the center console.

    I have the relays per Urs wiring diagram (upgraded to the purple/brown). Under the dash, I am aware that there is one different Relay and confirmed that it's in the right spot (Ferrari kindly puts a paint mark on that socket). So it's unlikely to be a relay problem since I checked those but I will check again.

    The strangest thing IMO is that removal of that relay does not turn the light off that's connected to the heater valve socket. Even though Urs diagram shows that as the "heater valve relay"

    Steve Magnusson thanks for checking in. It's a 1985 QV (I've updated my profile)
     
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  7. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
    Uk
    Are you sure someone has not rewired the relay base to in effect bypass it
     
  8. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
    Uk
    Looking on the wiring diagram i see the electro valve for the water flow to the heater unit, but the only relay i can find is that on the fuse board. Valve as 2 wires, one is marked MB- brown striped white which goes to C14 and then to the electronic temp control unit.
    Other wire is BR-white striped red, goes to C11- connector for central tunnel behind passenger foot rest.
    Does that help ?
     
  9. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Thanks Mike.

    I have this diagram and have traced the wires and relays - as well as done the tests in the other string. This is why I'm confused - I don't see any physical changes to wires (good thing this car does not appear to have any altered wiring) so I don't think it's been changed although that's still a possibility.

    I'm printing the workshop pages and will test the values at the pin.

    I've tested the relays and what's strange is that pulling the relay for the heater valve seems to have no effect on anything - the light still stays on. Only pulling the plug from the HVAC unit cuts the light, or grounding the pin on the internal temp sensor.

    So again I've confirmed that my pot is working (0k - 10k ohms) but absolutely nothing I do can get the light to blink/turn off.
     
  10. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
    Uk
    The drawing is not showing a relay that i can see. My drawing is of a 3.2 qv euro. Put a meter across the valve wires and then disconnect one of them at the connector c11 or c14. You should lose the circuit. From what i see the
    Electronic unit under the passenger foot rest controls the valve action. Terminal 8 on C 14.
    If this valve is opening a variable amount then i would think it would need a variable voltage from the control unit
     
  11. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    I don't think the 3.2 is the same as the QV.

    I confirmed via the terminals at the HVAC unit that all the sensors are in spec! Let the car sit overnight and checked this afternoon.

    Ambient temp in the shop was 14c (about 57 deg)

    Heater Temp Sensor (Spec @14c 1646ohms), actuals 1669ohms
    Evap Temp Sensor (Spec @14c 4537c), actuals 4340ohms
    Car Inner Sensor (Spec @14c 1699ohms), actuals 1750ohms

    All of these will within range of between 13c - 15c Ambient so I feel like the sensors are good.
     
  12. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
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    You can have all these reading but you need to see if the valve is getting volts and what happens when you remove the volts, ie prove the valve . If it works then you are back to this control unit which is generating the signals
     
  13. Steve Magnusson

    Steve Magnusson F1 World Champ
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    I can't find any relay called "relay for the heater valve" in either the 308/84 OM nor the 1984 Mondial QV wiring diagram book. Can you identify it by its letter given either in the 308/84 OM or the 1984 Mondial QV wiring diagram book Fig 11 or relay section?

    Have you checked the condition of the small fuse in the AC fan speed potentiometer assembly? (Not sure that this would have anything to do with the heater valve operation, but want more status).

    Also, is this something that was working and suddenly failed, or is it something that has never worked since you bought the car?
     
  14. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
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    I cant find this relay either on my 3.2 drawing, the valve is wired to this electronic temp controller under the passenger footrest, using terminal 8
     
  15. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
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    I have not checked that fuse Steve, because the Heater fan blower works fine at all speeds. So never looked at it but I will.

    It never worked. When I got the car a few weeks ago, there was no heat. Being familiar with Mercedes of this era I was aware of the broken monovalve rubber, so assumed that was the problem. Removed the heater valve and the diaphragm was in fantastic shape so I ruled that out. When I disconnected the wire I got heat, so I knew it was electrical.

    I saw some of the other posts on this so wired a dash light into the terminals for the heater valve to test the system. No matter what test I've run, I'm unable to get the light to blink/dim - I'm getting constant 12v the whole time. This is what started the search to repair it, since I know the pot is working (verified 0k - 10k at the pot), and verified all the sensors are in spec, and verified everything is physically connected.

    I'm using Urs wiring diagram. The one I'm referring to is the SIPEA 0440 (purple) relay above. It's part of a cluster of 3 relays under center of the dash (at the end of the center console).

    I only have the 1983 factory wiring diagram (if you have a link to the 1984 I would love it), but on Figure 11 There are 3 relays - C, M, and N.

    C = Blower Motor Relay (SIPEA 0442)
    M = Relay for Elecrovalve (SIPEA 0440)
    N = Relay for A.C. Compressor (SIPEA 0442)

    The 83 wiring is different slightly from Urs so I assume it's a change from 83-85. However I think the factory manual has swapped M and N.

    The Ferrari wiring doesn't show the internals of the HVAC ECU (Urs does), but that Purple relay goes to the ECU at Pin IV which is labeled (heater valve control) (brown/white wire) and also looks like it's directly connected to the ground of the heater valve wiring (brown/white). The red wire goes to Pin III on the HVAC ECU
     
  16. Steve Magnusson

    Steve Magnusson F1 World Champ
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    This link:

    https://www.dropbox.com/s/4kpwkx0in6g6xkl/Wiring Diagrams Mondial QV 1984 US Version.pdf?dl=0

    should get you a pdf copy of the 1984 Mondial QV US version wiring diagram book (and I believe 1985 US Mondial QV are the same). In this one, too, in Fig 11 they wrongly switched the descriptions for relays m and n (Urs' figure has it right). The reason that you always get +12V between the heater valve terminals even with the heater valve relay removed is that that terminal on the heater valve is still also connected to HVAC ECU -- so the HVAC ECU can still "hold" that terminal at ground (even if it's doing so wrongly).

    If you've verified that all the input signals to the HVAC ECU are OK, but the HVAC ECU still holds the heater valve closed when requesting heat = have to, unfortunately, say that that isn't a good sign for the HVAC ECU itself. Good Hunting!
     
  17. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Thanks for the link, Steve.

    So a used ECU is coming from the UK and should be here this week. In anticipation of this issue I ordered one last night. We'll see if this fixes the problem.

    It looks like they are available new, too still from Ricambi. I'll be perfectly happy to spend the $$ if this solves the problem since everything else seems to be good.

    Wish me luck!
     
  18. afterburner

    afterburner Formula 3
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    #18 afterburner, Mar 11, 2020
    Last edited: Mar 11, 2020
    When I upgraded the 3 relays I found that the original SIPEA relay had different terminal positions from the modern Hella.
    I had to switch wires around to get the same function.
    Please verify your wires are going to the correct terminal on the new relay.

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    The sockets can be detached by pressing the middle area spring clip and then sliding then vertically down.

    Sorry for the late reply I was traveling overseas.

    Hope this helps
    Urs
     
  19. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Thank you! I haven't changed the relays at that area yet in order to keep the amount of diagnostics down.

    Is the wiring in these pictures correct for the new relays?
     
  20. afterburner

    afterburner Formula 3
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    Yes it is - those are from my own car.
     
  21. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Know that you've already moved on to trying another HVAC ECU, but, for completeness, I really should've written:

    If you've verified that all the input signals to the HVAC ECU are OK and the +12V power and ground signals to the HVAC ECU are OK, but the HVAC ECU still holds the heater valve closed when requesting heat = have to, unfortunately, say that that isn't a good sign for the HVAC ECU itself.

    Side question: Does the HVAC ECU run the AC system properly?
     
  22. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Thanks Steve - I'll double-check but I assume the answer is yes although it's worth confirming.

    The AC doesn't appear to be working, however I have not got that far yet. I have no idea the state of the charge in the system and I get an occasional Yellow light on the Check Control Unit. When I press the AC button nothing happens but honestly I've left it alone at this point to try and get the basic heater working.
     
  23. afterburner

    afterburner Formula 3
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    Jun 20, 2008
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    AC - the clutch trigger relay is a micro-relay in the ECU that on my car burned out at one stage.
    It's worth opening up the ECU to have a look.
     
  24. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    So funny I pulled the relay apart and it looked fine inside - almost brand new actually. But I’m not great with electronics so not sure how to test it :(
     
  25. mike32

    mike32 Formula 3

    May 13, 2016
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    A relay is just a switch. It will have a load supply wire and a load outlet wire. Also a coil which gets a signal applied to it, when it gets the signal the coil is energized and it makes the connection from the load supply wire to the load outlet wire. You can rig up a 12 volt supply to the coil and you should see the relay operate. That is the simple sort of relay and there are other variations on this.
    The relay may have a diagram on the side of the cover to show its internal layout.
     

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