5 Amp Fuse Blows York Heat Pump

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Old 03-23-20, 06:12 PM
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5 Amp Fuse Blows York Heat Pump

York Heat Pump Model #B3HP024A061
Unit ran fine all winter. We had a warm-up here in Tennessee and switched to A/C.The heat had not been on in a few days. Nothing happened. No blower, no compressor...nada. Could not even get the fan to run. Replacing batteries did not help.
The old Honeywell programmable thermostat always drove us crazy and was sometimes displaying random characters so I bought a T2 Honeywell non-programmable. Still nothing. I did a lot of reading and found a blown 5 amp fuse on the fan control board. Replaced fuse and it blew again. Same symptoms. No fan, no compressor, just dead in the water. I wondered if I wired it wrong, but it was still doing the same thing before I replaced the thermostat. I read it could be a low voltage short (24v )Pulled service disconnects and checked contactor per a video I saw. Its checked good. I got 8 ohms on the coil and I have continuity on each side when I held the actuator down. Thought it may be a short in the wire from unit to thermostat. I pulled the thermostat face off and disconnected the wires from the fan control board and checked for a short between them. No short found. I am wondering if 8 ohms is ok for the contactor or if that is too low. Plus, most all the reading I have done has you measure between the common (blue) wire and other wires. This unit has the blue wire disconnected at the fan control board as well as the thermostat. Has been running fine for the past 5 years like this. I really don't have any idea where to go from here. Any advice would be greatly appreciated.
Thanks in advance!
 
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Old 03-23-20, 06:38 PM
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You could disconnect the stat wires at the furnace/air handler and see if it blows the fuse if you jump between the R and G terminals. The fan should start. If it doesn't then you have an issue with the stat wires or the condenser wires. Note: the condenser low voltage wire does not normally go to the stat.

Check outside and see if the low voltage wire to the condenser is damaged between the house and unit or inside the unit. I wouldn't be surprised if maybe a mouse chewed the insulation causing a short that blows the fuse.
 
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Old 03-24-20, 04:23 AM
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Thank you for the quick reply Tolyn. I will disconnect the stat wires and jump R & G terminals and check for the fan.
I did have the stat face off and the stat wires disconnected from fan control board and checked for shorts between each wire and did not find any shorts.
I really appreciate the help. It got into the 30s 2 nights ago and was pretty chilly in here!
 
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Old 03-24-20, 10:18 AM
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Red is the 24vAC supply line.
That 24v is connected to each of the following colors depending on function selected.

Orange to red to activate the reversing valve in cooling mode.
Green to red to activate blower.
Yellow to red to activate the condenser.
White to red to activate the electric reheat coils.

At the thermostat you can jump from red to each color to see which one blows the fuse.
I'd also recommend changing to a 4A fuse to protect the 24v transformer.
 
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Old 03-24-20, 01:57 PM
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PJmax!
Thanks so much for your advice and help!
I will get the 4 amp fuses as recommended.
As you directed I jumped:
Red to Green=Blower ok
Red to Yellow=Condenser ok
Red to White=Heat ok!!
Red to Orange=ok
Fuse did not blow.
I'm surprised to say the least. Called Honeywell thinking there was something wrong with the new thermostat or I wired it wrong. Tech went over the wiring with me and it was correct. Programmed options were correct. I put the thermostat face back on and as soon as I did, the heat and fan came on. Checked the A/C while he was on the line and after the delay, it worked fine also.
He did not have an explanation.
I'm just glad not to be cold but....I don't have that warm fuzzy feeling about all this.
Going from blowing fuses to no problems.
What do ya call it..."intermittent"
 
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Old 03-24-20, 03:26 PM
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If you went to use the A/C and that's when the system failed...... it's likely to have a problem in the wiring from the house to the condenser..... and more precisely inside the condenser to the reversing valve. This valve is only energized for cooling mode..... not heating mode. We've seen wiring shorts inside the condenser on a sharp metal edge.

Keep and eye out. The fuse blew and more than likely will blow again.
 
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Old 03-24-20, 04:08 PM
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Thank you so much, PJmax.
Makes sense.
I never opened the access panel on the opposite side to check anything. Only the panel where the control board resides. Believe me, that will be the first place I look when this happens again. So the reversing valve solenoid wire comes off the defrost board, if I am reading the schematic correctly?
I really appreciate your advice.
 

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Old 03-24-20, 05:12 PM
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Yes..... the orange wire controls the reversing valve. It may change color inside the unit. The valve may be visible looking down thru the fan opening.
 
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Old 03-24-20, 05:59 PM
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Good deal.
This gives me a good starting point of what to look for and where to look.
I have learned a lot.
Thanks for sharing your knowledge!
 
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