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monsterbuck · Jun 16, 2009, 04:29 PM

Central Air - Goodman
Furnace - Tappan
Thermostat - Robertshaw (Programmable)

I keep blowing a 3 Amp fuse that is located on a computer board inside of my furnace panel when turning on the Central Air unit. I've replaced the fuse and was able to run the furnace and the blowing fan just fine, until I turn the AC on. This blows the fuse and the furnace, blowing fan and AC all cease working. Replace the fuse and furnace and blowing fan work fine. Went outside and made sure fan on AC unit was freely moving and it was fine. Threw breaker in my house electrical panel to the AC unit and switched thermostat to cool mode and blew the fuse again. So I think I've found out that the outside unit is fine, if I'm blowing the fuse when the power to the AC unit is off?? Do I have a bad transformer inside the furnace?

Thanks in advance for the help!

Kurt

mygirlsdad77 · Jun 16, 2009, 05:04 PM

I almost guarantee that your contactor in outside unit has a short on the low voltage coil.

Unhook thermostat wires from contactor on outside unit, turn thermostat to cool and let me know if fuse blows. If it doesn't, you will need to get a new contactor. This really is an easy part to replace and doesn't cost all that much. Please let me know what you find and how things turn out, or if you need more help, come on back. Good luck,, and I really think this is the problem, if not, check thermostat wires near unit to make sure they didn't get cut by(dog chewing on them, weedeater, lawnmower, etc, etc). IF wires shorted together, it will also blow fuse, but usually it's the contactor itself.

monsterbuck · Jun 16, 2009, 05:57 PM

Thank you very much! You're awesome! I think that's the problem... I unhooked as you said, turned thermostat to cool and furnace fan kicked on! All that was happening before this was the fuse blew. Looks like a simple fix as long as I can find a new contactor. Should I be concerned with the compacitor that is sitting next to the contactor if I have the power off?

mygirlsdad77 · Jun 17, 2009, 04:14 PM

Yes, don't touch the leads on capacitor with bare hands unless you use an insulated screwdriver to short between leads first. This will discharge capacitor if it is charged and then you can touch it all you want. If you touch both terminals on cap at same time when its charged, you will get one hell of a jolt. The shock won't last long but the memory will stick with you for a lifetime. In changing the contactor, you shouldn't have to touch capacitor, so you should be all set.

Remember all above advice is with power to unit off, 24 and 240v.

monsterbuck · Jun 21, 2009, 04:12 PM

Thank you so much for your help! I've replaced the contactor and it's cooling better than ever!

mygirlsdad77 · Jun 22, 2009, 03:31 PM

Glad to hear it. Good job.

nspectr64 · Mar 9, 2014, 02:26 PM

What if the fuse blows after you disconnect the thermostat wire from the contactor?