Honeywell Ultra sx80 blower stuck on!

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Old 01-09-13, 03:41 PM
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Honeywell Ultra sx80 blower stuck on!

Hey all,

WE Are building a new shop and finally got the new furnace and thermostat installed. After flipping the power switch the blower fan came on but not the exhaust fan. After some testing we found the 24v transformer was putting out only3 volts so that was replaced. Were still having the same problem. Fan won't shut off even with thermostat disconnected. I'm just a handyman so not much furnace experience.

Also there its no ignition...

Ignition module its Honeywell s8600c. Fan board is st9120c. Any help is great!
 
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Old 01-09-13, 04:38 PM
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Do you have 24VAC between R and C?
 
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Old 01-09-13, 08:54 PM
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my friend may or may not be able to respond. we got the furnace to run now but the fan will not turn off.

I figure one of the three relays is stuck? any ideas which?

turned out the fuse was missing and solved our first issue
 
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Old 01-09-13, 09:07 PM
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make sure thermostat is not set to fan ON.

Remove G wire from thermostat
- fan shuts off = bad thermostat or set to fan ON
- fan stays on = remove wire from G terminal in furnace
- fan shuts off = bad thermostat wires
- fan stays on = bad control board (stuck relay) or fan wired wrong

FYI, that furnace is KNOWN for cracked heat exchangers.......... How old is it?
 
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Old 01-09-13, 09:53 PM
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so i was right, we have a stuck relay.

I have no idea how old the unit is, we just bought it used, the exchangers look immaculate and like new unlike our other furnace with had surface rust on the exchangers

any idea which relay? I can solder in a new relay much cheaper than replacing the board
 
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Old 01-09-13, 10:14 PM
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no, and you should not solder a relay on any hvac control because you are basically unlisting the UL listing and making it your own listing. If something were to happen in the furnace that caused major damage to your shop and the insurance company found out your did something to the hvac control you would be liable for all repairs and they would likely not pay a dime. This is just the way the industry works. If you want to and can replace the relay or all of them then have at it, just know you are assuming all liability.
 
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Old 01-10-13, 01:31 PM
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In addition to HVAC tech's wise counsel, replacing the circuit board renews many other parts and furnace systems, which typically improves reliability in the future.

Quack doctoring furbnace circuit boards should not be done.
 
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Old 01-11-13, 03:58 AM
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yes because a 4 year degree in electrical engineering and 5 years experience and I'm suddenly a "quack". THANKS
 
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