Temp of Relays in Passenger Footwell Fuse Box? | FerrariChat
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Temp of Relays in Passenger Footwell Fuse Box?

Discussion in '348/355' started by whyte, Apr 27, 2014.

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  1. whyte

    whyte Formula Junior

    Apr 25, 2006
    409
    Merritt Island, FL
    Full Name:
    John C
    #1 whyte, Apr 27, 2014
    I'm chasing an electrical gremlin that seemed to appear after tinkering with my fusebox area. I suspect I have one (or more) bad contact(s) or a ground, although it sure isn't apparent from the hours of tests I've done, resistance traces, etc.

    One thing I did notice is that many of my relays get very hot. My laser temp indicator showed the top row of metal relays with several in the 100-127 range, specifically the K relay, ignition and fuel pump relays. Bottom row were much cooler, but the ignition and fuel were warm there also, although not HOT like the top ones.

    If someone could pop their fuse cover after a drive and give me a ballpark (or exact) temp on the top row of relays, I would really appreciate it.

    I suspect this is the root of my problem, causing some idle and ignition flakiness as well. Any other general advice about grounding or contact issues is also appreciated.

    Thanks in advance!
     
  2. whyte

    whyte Formula Junior

    Apr 25, 2006
    409
    Merritt Island, FL
    Full Name:
    John C
    #2 whyte, Apr 28, 2014
    Token bump. Don't need an exact reading. Just a ball park ranging from cool, warm, to "I'm not leaving my finger on this" would be awesome. :)

    Thanks.
     
  3. Wade

    Wade Three Time F1 World Champ
    Owner

    Mar 31, 2006
    32,793
    East Central, FL
    Full Name:
    Wade O.
    #3 Wade, Apr 28, 2014
    I wish I could help but probably won't be able to drive mine until this weekend.
     
  4. Rally guy

    Rally guy Rookie

    Aug 3, 2006
    36
    Toronto
    Full Name:
    Robinson
    #4 Rally guy, Aug 30, 2017
    I have this problem too, and have a laser thermometer. Will post accurate temps soon. If I fiddle with them, the car runs way better. Did you diagnose the issue? My two hot relays are the M and N relays, fuel pump and ignition control relays.

    Rk
     
  5. m.stojanovic

    m.stojanovic F1 Rookie
    Silver Subscribed

    Dec 22, 2011
    3,290
    Serbia - Niš
    Full Name:
    Miroljub Stojanovic
    #5 m.stojanovic, Aug 31, 2017
    One source of heat in the relays is the relay coil itself but not really significant. Relays (in the case of 348) C, D, L, N (fuel pumps and injectors) and B (the K-relay) have 65 Ohm coils and will run warmer than the other relays which have 85-90 Ohm coils.

    A much more significant contributors to relay heat-up is the condition of its pins and its contact points inside. If the pins are somewhat oxidised, they develop resistance towards the sockets and the connection points become powerful heaters. The contacts inside the relay deteriorate (burn) over time and can also develop some resistance = heat.

    I think the relays should be pulled out say once a year and their pins inspected and cleaned. Also, just pulling them out end re-inserting (and doing this a few times) improves the connections of the pins to sockets. This is especially important for the rad fan relays (I & M) which carry very high current as well as the relays C, D, L & N.

    As for the relay contact points, there is nothing you can do in the case of Bosch relays but to replace them. I have replaced all relays on my 348 with Hella relays which can easily be opened and you can also clean the contact points inside.
     

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