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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8768
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a york diamond 80 my 6-1/4 amp fuse blowing up after

Customer Question

I have a york diamond 80 my 6-1/4 amp fuse blowing up after few minute running.
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.


So far it sounds like a bad fan motor( $150 for the part) or a bad fan motor run capacitor ( $7 for the part). The fan motors are good for 7 to 10 years run time, the capacitors sometimes fail a bit before that.

Tell me about how old the furnace is, and if you are near a Grainger Industrial Supply or Johnstone Supply store or not.

We can go from there.

Expert:  Phil replied 1 year ago.

If you want to measure the amperage draw on the motor you will need a clamp around type amp meter, $25 at harbor freight, $50 at lowes or home depot for a slightly better one.

Customer: replied 1 year ago.
I can't even get to measure amperage, it will only run for about 30 sec. I replace fuse-stat what they call 6-1/4 amps 6 times and its $7 a pop. Can i by-pass this fuse for a while for troubleshooting? do you recommend fuse or breaker?
Customer: replied 1 year ago.
Do you have the part # ***** the motor and capacitor? I'm close to Grainger store.
Expert:  Phil replied 1 year ago.

Hello again, there will be no benefit in bypassing the fuse, the motor will simply burn out if you do that.

You do not need a part number for the run capacitor, just remove it from the furnace and take it to Grainger for a match up... its most likely rated a 4 or 5 micro farads, and that is stamped on the capacitor as 5uf for example, and 370 volts (even though your furnance is 120 volts the capacitors are rated at 370 or 440v) Cost will be $7 or so.

Good luck with it, keep me posted, we can go from there.

Customer: replied 1 year ago.
Do i need to change just the capacitor? or both motor and capacitor?
Expert:  Phil replied 1 year ago.

Hello again, the motors last 7 to 10 years on average, some last longer. If there is *any detectable sideways play in the motor shaft at all, replace the motor... (end play is OK, its normal, that can be eighth to a quarter of an inch with no problem(.

I would start with a new capacitor and see how that goes, since those are only $5 to $7.