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Blower not coming on, kinda

Posted by dwall (My Page) on
Mon, Apr 25, 11 at 15:19

Ruud Furnace, AC, auto thermostat, 20 years old


I think I may have 2 issues/conditions.

1. Blower will not come on when TS set to Blower=On, or when TS commands cool.
2. Blower comes on by itself in summer.

A few years ago my blower limit switch was replaced and ever since then my blower just comes on by itself in summer, I assume this is no big deal and is caused by limit switch adjustment. Limit switch can turn on blower regardless of TS setting right?

Now my blower not coming on when cool command sent by TS, or when set to Blower=On. However blower still comes on by itself as described above.

If blower starts then capacitor is good right?

I am guessing Blower Relay is bad. I see a plate on left side, behind panel, that has transformer and I assume blower relay, sound correct?

I am very new at this, so forgive me is I have left out info or mis-named something. If my logic is off, please put me on the right track. BTW I can handle simple wiring and a VOM, and I have 2 units, upstairs and downstairs, I hate parts swapping, would rather test. I am wide open for experienced opinion.

Thanks very muchin advance. Help is greatly appreciated!!

Thanks, Danny

Follow-Up Postings:

RE: Blower not coming on, kinda

Sounds like you are on the right track. Check for 24 volts at the relay when the stat fan switch is on. If no 24 volts then could have a bad switch in the stat or a bad wire going from stat to relay. If fan switch is set at 120 on 90 off, run both up 5 degrees. also check that transformer for 24 volts.

RE: Blower not coming on, kinda

Thank you paul52446m, I replaced the transformer. Then I learned sometimes things cause the transformer to go bad, then I replaced contactor. Then had my local HVAC co come out and check freon, it was low, he charged two pounds.

How does he know how much? He said experience, I say a scale is the proper way. Do any professional techs weigh, or is that all gone these days.

Anyway thanks for your help, I'm cool for now with most likely a small leak somewhere, oh yeah, tech said leak would 99.9 % be in evap, then must replace entire system because of new freon and old together cause goo. That turned out to be way over hyped in automotive business! What say you in HVAC business?

Thanks again, Danny

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