mondial 3.2 heater control problem | FerrariChat
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mondial 3.2 heater control problem

Discussion in 'Technical Q&A' started by mondial5183, Mar 3, 2009.

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  1. mondial5183

    mondial5183 Karting

    Nov 17, 2007
    80
    #1 mondial5183, Mar 3, 2009
    Hi, i have a problem on the heater control. Indeed, i think that the heater control valve is closed every time. I tested it, and i found 12 v when the heater control is on cold or hot position. If i want heater in the internal of my vehicule, i have to remove the relay under the central aerator. Then the valve is opened.
    I tried to change the relay...i checked the control unit behind the passenger's foot...Anybody here knows how this valve works ?
    Thanks.
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,931
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, Mar 3, 2009
    Last edited: Mar 3, 2009
    Send me a PM with your email address, and I will send you a copy of the 488/87 Mondial 3.2 wiring diagram booklet.

    The way this heater valve works is that, when the key is "on", +12V is always on the BR (white/red) wire.

    When the "STOP" push button is pressed on the push button control unit, the relay m (...101) is not activated and the MB (brown/white) wire at the heater valve is directly connected to ground (via relay m) -- which passes a current thru the coil in the heater valve and holds it closed.

    When any other active push button is pressed, this should activate relay m and remove the direct ground signal from the heater valve MB wire. Now the MB wire is controlled by the AC ECU (in the passenger footrest). If the AC ECU "thinks" that no heat is required, it keeps this MB wire at ground, keeping the heater valve closed. When the AC ECU "thinks" it needs to add heat, it (internally) disconnects the MB wire from ground so this opens the heater valve. (And the good news is that when you physically remove relay m and the heater works, this is a good sign that the AC ECU and the temp sensors are OK.)

    The first test would be to just "feel" the outer case of relay m with your finger as you alternately press the "STOP" button and any other active push button (with the key "on" or the engine running) -- if you don't feel relay m clicking off and on, this is the trouble. Try that first, and report the results.
     

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