Inducer motor won't start, but no power in line

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Old 01-26-16, 10:20 AM
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Inducer motor won't start, but no power in line

I am coming to this forum to get some help on a strange problem of my furnace.

Furnace stopped working the other day, it is a HEIL H8MPT100F14B1 two stage gas furnace, built in 2006.

Inducer motor simply does not start.

Circuit board blinks three flashes, code is Low Pressure Switch open when should be closed.

first changed both pressure switches, same problem;
second, suspected relays, got new circuit board, connected everything exactly the same as before, still the same three blinks.

With multi-meter, measured W and C, 27V AC, so no problem for thermostat or thermostat wiring;
measured C and R, 27V, so transformer is working;
measured 115V output port for the inducer motor, found no voltage at all.

What could be the problem? I have brand new board and pressure switches.
 
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Old 01-26-16, 10:34 AM
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On a call for heat you should get 120vac on the inducer line. That 120v may be shut off in one minute. It could be restarted again or the board may go right into lockout.

So check for 120v within the first minute of a call for heat.
If nothing leave the board model number.
 
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Old 01-26-16, 04:12 PM
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Personally I'd be inclined to condemn the circuit board as being bad right out of the box.

The time a part is MOST LIKELY to be bad is when it is brand new!

Also, check very carefully to be SURE you have the new part connected properly.
 
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Old 01-26-16, 09:57 PM
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I find it unusual to have a board in service fail and a new replacement board to have the same exact problem.

Check the resistance of the inducer motor. (rule out a bad motor)
Check any connecting plugs and jacks CAREFULLY for corrosion. Those plastic housing connectors with the steel pins have been know to be corroded and intermittent.
 
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Old 01-27-16, 12:59 PM
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<<I find it unusual to have a board in service fail and a new replacement board to have the same exact problem.>>


True --- but I've had just that kind of thing happen.

<<Check the resistance of the inducer motor. (rule out a bad motor)
Check any connecting plugs and jacks CAREFULLY for corrosion. Those plastic housing connectors with the steel pins have been know to be corroded and intermittent.>>


Certainly worth doing.
 
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