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I have a Fujitsu 18C1 split type AC system that does not power up at all. I replace the condenser unit fuse and the wall unit fuse, but the system continues to blow fuses on the wall unit only. What might be wrong with my system?

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When you say wall unit I assume you mean indoor portion that circulates the cool air or the evaporator. Check to see if the fan will turn freely when unit is off. This fan should spin free. You could have a bad fan motor a shorted capacitator. This unit should have some type of a drain line to drain condensate. Be sure this hasn't gotten plugged up causing a moisture problem inside the unit. You could "unwire" the motor and see if this stops blowing the fuses. If it does, then your problem is isolated to the fan motor.

Posted on Jul 09, 2010

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  • duggdeth Jul 10, 2010

    OK. Here's what I found:

    (1) both the outside condenser unit fan and indoor evaporator unit fan spin freely w/AC off

    (2) drain line is clear

    According to these results, can I assume it's a shorted capacitor? And if so, which capacitor is likely to be the problem?

  • duggdeth Jul 11, 2010

    Another update on troubleshooting: I pulled the control board (Edition 06) from the wall unit and found scorch marks on the back of the board @ R2. Areas on the backside around R1, D1, D2, and D5 also looked like the solder heated up around them, but no scorching is evident.

    All the capacitors look ok, but I haven't put anything on a meter yet. Does this new info give you any more clue as to the nature of my AC problem? Better yet, is it possible to just buy a new control board and filter board rather than replacing individual parts?

  • Tom W Jul 11, 2010

    I viewed your last posting about black marks, and possibly melterd solder. If these terminals are for the relay that turns the fan on, it coudb be thatevaporator fan motor (or it's start capacitor) is shorted. Again, I would disconnect the blower fan motor. If the unit powers up now witout tripping breaker or blowing fuse, it would indicate you have a motor problem.

  • duggdeth Jul 12, 2010

    I disconnected the blower fan motor, and no change--although it didn't blow the fuse now either. There appears to be no power getting to the inside wall unit @ all. I traced the yellow molex connector from the control board (marked CN4 FANCAPA) to what I believe is the fan start capacitor? (a black box, approximately 1&1/2"x 3/4"x1&1/4"). It also doesn't appear to be "bad", although I haven't run a meter on it. What else can I do to try an fix this POS?

  • duggdeth Jul 13, 2010

    More new findings: the fan motor capacitor tested fine--no short/open circuit. Any other ideas you might recommend?


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