Relays under dash (behind centre console)? | FerrariChat

Relays under dash (behind centre console)?

Discussion in 'Mondial' started by belfry, Jan 18, 2019.

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  1. belfry

    belfry Formula Junior

    May 14, 2015
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    Robert Batt
    #1 belfry, Jan 18, 2019
    I have been in the process of replacing the heater blower resistor in the central ventilation vent. While tracing the wiring back to the connector plug under the dash I found some relays under there. Does anyone know what their purpose is? 1990 Mondial T RHD Image Unavailable, Please Login
     
  2. AndruL

    AndruL Karting

    Apr 4, 2018
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    AndruL
    #2 AndruL, Jan 18, 2019
    I don’t have the T but in the 3.2 those are relays for your max fan speed, heater valve and air con.

    What heater blower resistor were you referring to? There is no such thing. You probably meant the transistor in the center air vent?
     
  3. belfry

    belfry Formula Junior

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    Robert Batt
    #3 belfry, Jan 19, 2019
    Sorry. Yes, I meant transistor. I’m having an intermittent issue where the heater fan won’t work. I do have the ability to vary the speed of the fan (when it runs), so the transistor is doing what it’s supposed to.
    I wonder if I need to change these relays to see if this fixes the issue?
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #4 Steve Magnusson, Jan 19, 2019
    Last edited: Jan 19, 2019
    Probably not.

    This is more indicative of losing (and sometimes recovering) all +12V power to run the whole AC system. There is a ...113 (IIRC) relay in the main group of relays for supplying AC power, but an even more likely suspect is a burned connection in the white connectors on the main relay panel-PCBA. An easy first thing to do is just unplug all the white connectors and look for burned connectors/discoloring (it isn't visible when they are plugged in).
     
  5. belfry

    belfry Formula Junior

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    Robert Batt
    #5 belfry, Jan 19, 2019
    Thanks Steve.

    I will check for discolouration on the relays (on the main fuse box I guess?). One of the 3 relays under the dash was quite dirty and tarnished (centre one) so I've cleaned them all.

    I didn't replace the transistor in the heating vent as I have the ability to vary the fan speed.
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,144
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #6 Steve Magnusson, Jan 19, 2019
    Yes, at the main fuse box, but it's the unplugged connectors you need to check for discoloration/burning (not the relays).

    Correct - if the variable speed is working when it works, and maximum speed is not working when it doesn't work = very strong sign that the power transistor is OK, and the trouble is elsewhere.
     

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