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Old 12-25-2008, 07:04 AM   #1
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Blown 5 amp fuse on Carrier System


Hello, I have a Carrier central unit that keeps blowing a 5 amp fuse on the control board of the air handler/blower.

Problem began about a week ago when we went to adjust the thermostat and the digital display was blank.

Upon further inspection we discovered the 5 amp that had blown.

Upon replacement, the thermostat came back but the fuse blew again when the heat tried to turn on.

After this we inspected the wiring at the outside unit and found no apparent problems. We disconnected the main black wire from the outside unit and replaced the fuse, and the display came back again and the fan worked inside. When we reconnected the black wire at the outside unit it ran fine on Heat, and EHeat for about a week and has just blown again this morning.

I'm beginning to believe there is a short somewhere in the wiring to the outside unit. Both times we blew fuses it had rained heavily in the previous 12 hours.

If anyone can offer any tips or suggestions to help us speed along the diagnosis to our problem I would greatly appreciate it!


Last edited by chalkstar; 12-25-2008 at 07:09 AM.
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Old 12-25-2008, 09:28 AM   #2
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Blown 5 amp fuse on Carrier System


You are right it is a ahort. If you have an ohm meter than start checking for the short.

Barring that you may have a bad contactor in line to what ever form of heating you are using.

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Old 12-25-2008, 10:37 AM   #3
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Blown 5 amp fuse on Carrier System


Thanks for your reply. I am going to get to work with a meter as soon as I can finish all my holiday festivities. What a rotten day to have your heat go out!
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Old 12-25-2008, 11:09 AM   #4
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Blown 5 amp fuse on Carrier System


That fuse is for Control wiring only. I would check the condition of that small thermostat wire going to the outside unit. Look for signs of damage that may have been caused by mice chewing, or weed whacking -- things like that.
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Old 12-25-2008, 11:25 AM   #5
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Blown 5 amp fuse on Carrier System


agreed.
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Old 12-25-2008, 12:22 PM   #6
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Blown 5 amp fuse on Carrier System


I'll look into it and let you know what I find. Thanks!
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Old 12-31-2008, 11:45 AM   #7
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Blown 5 amp fuse on Carrier System


After a few days of searching (and not running my outside unit) I haven't found a short yet. We cleaned to contactor on the outside unit and tried to cycle on the heat. Now the thermostat does not go blank, but flashes a message of "HP" on the display. Any ideas? I can't seem to track this one down...
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Old 12-31-2008, 02:13 PM   #8
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Blown 5 amp fuse on Carrier System


Turns out the HP message was just a product of having the breakers off outside. We got the unit to kick on for a few seconds, before the fuse blew again. Afterward we found a short to ground associated with the board on the outside unit. Anyone know a good place to get parts?
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Old 12-31-2008, 05:16 PM   #9
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Blown 5 amp fuse on Carrier System


Quote:
Originally Posted by chalkstar View Post
Turns out the HP message was just a product of having the breakers off outside. We got the unit to kick on for a few seconds, before the fuse blew again. Afterward we found a short to ground associated with the board on the outside unit. Anyone know a good place to get parts?

Dang those Gay electrons always blowing something
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Old 07-22-2014, 11:18 PM   #10
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Blown 5 amp fuse on Carrier System


Hi Chalkstar,

I am facing the same issue as you for the carrier thermostat with blowing fuses (3 times in 2 weeks when it rained!). Would you describe the short circuit part on the control board in detail? Thank you!

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