Trane condenser fan issues and OFT A and OFT B


Old 06-06-19, 07:42 AM
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Trane condenser fan issues and OFT A and OFT B

Retired HVAC tech from late 1970;s. Question around a work around I did that most have said should be just fine - wanted to check in with some other experts. Working on a Trane TWY030A100A5 outdoor unit (XL-1400). Had been experienced intermittent condenser fan issues, sometimes it started with the compressor and sometimes not. Checked the electrolytic 5 uF cap and it was fine. Replaced it anyway due to age with a new Genteq. Replaced contactor - pitted contact points, but was still working. I tested continuity on the Fan Relay on the defrost board and it was fine (is a N.C. type and normal closed). What the issue was, was the OFT A/OFT B sensors that cut the fan down to a lower speed, under certain moderate temp conditions outside. What i found inside the outdoor unit was only three wires coming from fan and into control area (might have been four at the fan, but maybe someone cut it). Also, someone had put a wire nut on the low speed red wire coming from one of the OFT B. I simply bypassed both OFT's and took the Blue/Black wire from T2 and connected it to the high speed black fan wire ("R"). All works just fine now, condenser fan runs high speed all the time.

Should i look to replace the fan with a correct two speed one and in addition replace the THT0741 and THT0744? That would cost me wholesale $350 and would it really gain anything on an old unit from 1996?
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Old 06-06-19, 06:12 PM
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Welcome to the forums.

My forum partner, Houston, might be able to answer it better
but I see no problem running the condenser fan on high speed.

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