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
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
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)
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.
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
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.
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