Ruud Furnace - Blower Fan Not Coming On Automatically - HVAC - DIY Chatroom Home Improvement Forum

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Old 01-04-2012, 12:14 PM   #1
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Ruud Furnace - Blower Fan Not Coming on Automatically

HI all,

I hope someone can help with this, even just to confirm my current course of likely getting a professional in, after some attempts at dyi.

I have a Ruud UGAC-09KC Model Furnace. It is likely about 10 plus years old, and came with the house I just bought.

Here's what works:
-The thermostat (new), calls for heat, and the heat ignites and comes on strong, very nice flames, I've cleaned out the burners even.
-The fan works when turned to "on."
-The limit switch (what I initially thought was bad) is brand new, and appears to work as it should, raising as the heat stays on, clicking at 150 to turn on. To verify it works, it also turns off the heat at 200.
-The relay. I bought a replacement one, and tried it all with the new one on, nothing.

Here's what doesn't work:
-The heat comes on, the limit switch moves, but when it hits 150 and clicks, it does not turn on the fan automatically, as it should, being set so at the Thermostat.

Any suggestions? Thoughts? Need more info to help me? Let me know. Any help is greatly appreciated, as I thought the replacement of the limit switch and now the relay would have solved things.

thanks! Love this forum!


Last edited by mattach; 01-04-2012 at 01:39 PM.
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Old 01-04-2012, 09:20 PM   #2
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Blower relay may be faulty. Calling for Fan from the stat uses cooling speed. The limit uses heating speed.


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Old 01-05-2012, 07:55 PM   #3
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If its a dial limit it's definitely older than 10yrs old. Sounds like you need new limit. See if when it clicks you get 120v to the motor or not. You should have 120v to the limit then when it clicks you should have 120v out of it.
BrandonKJN is offline   Reply With Quote

blower fan , furnace , ruud

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