Helping diagnosing serial communication error with Fujitsu mini-split

mattmia2

I don't think you needed a meter for that.

Looks like it is a 10 a 250v fast acting fuse. The next question is what blew it.

Sethamin

mattmia2 said:
 The next question is what blew it.

So around the time that this system stopped working, I had a separate mini split system being installed (Mitsubishi 48k BTU condenser + 3 heads). They were wiring the condenser up on the day the fuse most likely blew. It's on a separate circuit but the same panel. What could they have done to cause this?

(They of course swore up and down that they couldn't have caused an issue, but the timing is suspicious to say the least)

109A_5

@Sethamin, with the violence that fuse failed with there may be something else wrong with the board or the motor or the wiring. To maintain the manufactures safety features the fuse should ultimately be replaced with the same type and value. The fuse's letter code should be on one of the metal caps, like AGC as the ones in the HD link for example. The same fuse may be available from other vendors besides Fujitsu. To me it looks like a 'Medium Blow' or a 'Slow Blow' fuse. The AGC fuses from HD are fast blow and may not last with motor loads. As a quick test I would probably use the HD fuse.

Replace the fuse with the safety switch or circuit breaker off.

Sethamin

Replaced the fuse and everything is working again! Except that the compressor sounds a little noisy now. Hope that's not a bad sign ..

Illinois_Sam

Where was this fuse located? Your photo of the wiring diagram, was it in the front cover panel?