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My A/C indoor PCB blower runs about 40% slower than from new.

I have replaced all capacitors, blower motor. BUT yesterday I noticed I didn't check for one specific capacitor. It says: 0.22 μF (220 nF) but after desoldered it said: 956 pF which is wayyyyy too low. The one in the picture:

Front View

Rear View

Film Capacitor

My questions:

  1. I know if the capacitor is devalued you should replace it, but do you really think it could be the reason the blower spins noticeably slower?

  2. Can I replace that film capacitor with a polyester with the same value (220 nF 275 V AC if the temperature is met)? I heard something about frequencies, but not sure.

Similar to one of these:Polyester Capacitor

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  1. That capacitor is for mains filtering. I don’t think it would affect the blower speed.
  2. No. The original capacitor has a X2 rating which means it is rated to be placed across the mains. This is a safety issue. X2 rated caps should be easy to source - even harvesting them from defunct power supplies and consumer gear.

The fan/blower looks like it is controlled by TR202 and associated circuitry. The big black capacitor might be more likely to affect fan speed. It’s labelled C-FM ( capacitor fan motor??) so that might be a hint.

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  • \$\begingroup\$ Yes, the big black capacitor you 're talking about has been replaced. I do not know how to test that triac: TR202. Somehow i believe what gives the frequency to accelerate the blower motor is getting fewer cycles or duty levels. \$\endgroup\$
    – Panamanian
    Commented Jun 13 at 0:29
  • \$\begingroup\$ My bad, forgot to ask you @Kartman, do you think C330 (next to blower fan connector) could be also the reason? (I did not measure it). \$\endgroup\$
    – Panamanian
    Commented Jun 13 at 5:46
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    \$\begingroup\$ Moreover, polyester is a type of film capacitor. \$\endgroup\$
    – winny
    Commented Jun 13 at 8:10
  • \$\begingroup\$ C330 looks to be only filtering. Nevertheless, it is worth measuring. It could be the opto PC309, C111,R119 or it might be the power supply or the controller? You’ve not told us what the exact fault is apart from fan speed. Does the fan always run? Knowing the symptoms removes some of the guesswork. \$\endgroup\$
    – Kartman
    Commented Jun 15 at 0:24
  • \$\begingroup\$ @kartman optos are only in two states, right? conducting or not conducting, no mid terms as far as I know. So all they conducts (the little led between pin 1 and 2). There's no fault exactly, only about 30% slower spinning and no C-FM capacitor is good 1.49 out of 1.5uf. \$\endgroup\$
    – Panamanian
    Commented Jun 30 at 22:57

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