York Diamond 80 Still Short Cycling!

Old 01-27-22, 09:46 AM
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York Diamond 80 Still Short Cycling!


First post here and am hoping for some assistance!

I have a york Diamond 80 Model P4DNA12N06401A

It has been short cycling

I have changed flame,sensor, high limit (plastic square mounted on unit box), limit on burners, cleaned the A Coil, cleaned the blower motor...

I jumped the sensor that is on the blower housing (part is not easily found since it is discontinued.

I had a tech out and have confirmed the heat exchanger is good and see no obstructions in the ductwork..

What am I missing?

This unit is about 18 years old and runs great....I'd appreciate any tips from someone who knows these units!

Thanks so much
Old 01-30-22, 08:51 PM
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You need to figure out what's actually causing the furnace to shut down - is it losing a call for heat, is one of the safeties open.

Need to use a multi-meter, not randomly jump things out.
Jumping out safeties can be very dangerous.

Looking for 24v ac if the safety is open, 0v if closed, assuming the circuit has power.
The flame sensor current can be checked by setting meter to dc microamps and wiring in series - bad ground, dirty burner can cause low current despite having a new sensor.

A competent tech should have no issues figuring this out.

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