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Coleman EB23B heat pump: Air Handler Humming Loudly, Blower Runs

Coleman EB23B heat pump: At the air handler, inside house, humming/buzzing starts the instant the fan knob on thermostat in turned on (while in Cool mode and Cool ''Off'' also). Blower starts in a second or 2 but the hum is instantaneous with turning on at thermostat. Blower seems to run ok but hum continues and ceases only when blower turns off. Replaced the run capacitor on blower but no change in hum as described above.
Blower motor had big clumps of dust on back and is likely dirty inside but squirel cage spins easiliy when pushed by hand.
There was a clogged pan drain pipe that was overflowing (the cutoff float switch was submerged and did not turn off the unit as intended. I cleared the drain and it now drains).
Why is this thing still humming/buzzing? Is the fan needing cleaning, is it going bad? Something else maybe?

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If you're mechanically inclined - and you seem to be - with all the stuff you've already done - you should be able to 'fix' this problem - if you decide to after reading what I have to say.

First of all - the humming you hear is most likely your 'fan relay.'

The fan relay is nothing other than an electrical coil that is enerigized by 24 volts from the thermostat. Once it's enerigized - it snaps together a set of points (usually copper) which completes a circuit sending 115 volts to your inside fan motor.

These 'fan relays' are notorious for 'buzzing' especially when they are wore a little. If it was me - I'd change it out to keep from having to deal with it at a bad time, i.e. 4th of July - Labor Day or just a lazy weekend.

If you decide to do this yourself - just be sure you have all voltage off before you mess with it. The relay is easy to find - just trace the line voltage wire - from the relay to the motor or vice versa. It (the line voltage wire) might go to a terminal block (although I doubt it) in which case you just need to determine which wire on the terminal block goes to the fan motor. In any case the relay will probably be black and it will have 4 wires going to it. 2 of the 4 wires will be the low voltage (24V) and the other 2 will be the line voltage (115 volts).

When you remove the relay just be sure you label all your wires so you can replace them on the new one just like they came off the old one. Usually the low voltage wires will go to the terminals marked 'coil' and the line voltage wires will go to terminals marked line but not always. The low voltage wires may go to numbered terminals that has a picture of a coil and the line voltage wires will go to numbered terminals that show an open wire connection.

Try and get an exact replacement but if you can't - have the parts man explain to you (if need be) which are the low voltage terminals and which are the line voltage terminals.

You'll probably have to go to an Air Conditioning Supply House - I doubt if Lowes or Home Depot will have the relay - but hey - it's 2010 - they might have it. Might be worth a try.

Also - if you have a buddy or relative in the AC business you might see if he/she would go by and pick you one up. Some AC Supply houses sell 'wholesale' to everyone but most - sell 'retail' to the general public.
So, if you can get it wholesale it will save you a few bucks.

Last thing... since I'm not there to look/listen to the buzzing - there's a small chance it could be something else - but I doubt it. Also, sometimes if you just 'tap' the relay with a screwdriver or pliers it might stop the buzzing - although I doubt it will stay quiet - it'll probably start buzzing again - but - then again - it might not.

Hope I've helped - and it's something different - get back to me.

good luck!

Posted on Jul 29, 2010


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