348..... AC compressor 30A fuse

Discussion in '348/355' started by marc556, May 16, 2018 at 11:17 AM.

  1. marc556

    marc556 Formula Junior
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    Jul 15, 2007
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    Wiltz (Lux)
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    Marc Foyen
    I've written this thread in the Technical Q&A part, but I'm not sure that you saw it.
    So I put it here-under


    Dear all,

    as some of you know, I have to work on the electric wiring of my 348, it will be done the next weekend.
    I also want to take the time to modify the followed thing...
    I want to replace the 30A fuse used tor AC compressor + Fan + Heater ECU by 3 separate fuses:
    30 A for AC compressor
    10A fan
    5A ECU.

    Do you know the colors of the wires ?
    I can imagine that some of you did this modification, so maybe you can share some pics to help me.

    Thank you so much
     
  2. Qavion

    Qavion Formula 3

    Feb 20, 2015
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    Ian Riddell
    ECU power wire colours mentioned here, Marc...

    Dead HVAC/AC panel

    Miroljub may be able to tell you if these fuse values are ok. Were you thinking of keeping the 30Amp master fuse?

    Full diagram here:

    F348 HVAC Wiring Diagram
     
  3. m.stojanovic

    m.stojanovic Formula 3
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    Miroljub Stojanovic
    Not quite correct - the main consumer is the blower fan so you should go as follows:
    30 A for Blower Fan
    10A for AC Compressor Clutch (its current draw is in the range of 3-5 Amp)
    5A ECU (the heater pump draws about 2 Amp and the rest is small so max. draw should not exceed 3 Amp)
     
  4. BT

    BT F1 World Champ

    Mar 21, 2005
    14,387
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    Bill Tracy
    I had Tim Stanford convert the A/C fuse to a breaker when I first got my 348 back in 2004 or so. He indicated that the fuses can overheat the fuse block and cause all sorts of problems or possibly even a fire if left as-is from the factory.
     
  5. marc556

    marc556 Formula Junior
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    Marc Foyen
    So that means it is very important to modify.....
     
  6. John Glen

    John Glen Karting
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    Dec 30, 2009
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    John Glen Wesanko
    I did a similar type mod on my 90 348 ts. I replaced the 30 amp fuse with a resettable aircraft 35 amp circuit breaker. Simple and effective. JGW
     
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  8. Qavion

    Qavion Formula 3

    Feb 20, 2015
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    Ian Riddell
    As long as you don't treat the circuit breaker as a switch, it's a good idea. e.g. When you see a fuse holder melt on a fuel pump circuit and you have to repair the fuse holder and wiring, you have a really good incentive to check out the circuit components properly before powering up the repaired circuit. With a circuit breaker, it's tempting to just reset it.

    I recall that the Boeing Maintenance Manual says that you have to replace circuit breakers if they have been tripped. Having said that, I think that rule was bent quite a few times in the real world. CBs do break, but it's rare.
     
  9. John Glen

    John Glen Karting
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    Dec 30, 2009
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    John Glen Wesanko
    I wouldn't worry about an a/c quality circuit breaker. Having worked as a licensed aircraft mechanic for several decades I've seen "breakers" used as switches for fuel pumps and other circuits continuously for decades on the same aircraft and never replaced. The chances of having to reset the breaker enough times to render it unserviceable are very small and it won't heat up like a fuse. JGW
     
    Wade likes this.

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