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Old 10-09-2012, 05:06 PM   #16
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Can't locate fuse on heat pump circuit board


You'll need to check for shorts before you install the new transformer, and power it up.

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Old 10-09-2012, 08:11 PM   #17
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Can't locate fuse on heat pump circuit board


Put a inline fuse(3amp) in series with the control voltage. It will prevent you from destroying the new transformer if you dont find the short!
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Old 10-18-2012, 07:30 PM   #18
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Can't locate fuse on heat pump circuit board


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Put a inline fuse(3amp) in series with the control voltage. It will prevent you from destroying the new transformer if you dont find the short!

Thanks for the great advice. Finally got transformer today. Installed 3A fuse in between control voltage and tuned on power. Started with heat on thermostat, turned on right away. Switched to a/c, fuse got blown. If there was no fuse, transformer could have been fried again. Installed new fuse heat worked again. Turned everything off and went out to a/c unit. Switched off the power to the unit and opened the cover. Nothing seems to be short. Capacitor checked good. Visually checked all cables good. Turned on A/c and fuse again was blown. Now heat/ fan are working, what should I be checking? Earlier I had tried to start outside unit by direct contacts and unit came up. Good thing it is in fifties here and just need heat. Have time to work on A/C. So where should I start now? Thanks again to all and this site for great advise!
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Old 10-18-2012, 08:32 PM   #19
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Can't locate fuse on heat pump circuit board


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Thanks for the great advice. Finally got transformer today. Installed 3A fuse in between control voltage and tuned on power. Started with heat on thermostat, turned on right away. Switched to a/c, fuse got blown. If there was no fuse, transformer could have been fried again. Installed new fuse heat worked again. Turned everything off and went out to a/c unit. Switched off the power to the unit and opened the cover. Nothing seems to be short. Capacitor checked good. Visually checked all cables good. Turned on A/c and fuse again was blown. Now heat/ fan are working, what should I be checking? Earlier I had tried to start outside unit by direct contacts and unit came up. Good thing it is in fifties here and just need heat. Have time to work on A/C. So where should I start now? Thanks again to all and this site for great advise!
you have a short in the control wire to condenser..that will blow fuse..or a contactor coil short... that will also blow a fuse..ben sr
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Old 10-23-2012, 08:33 PM   #20
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Can't locate fuse on heat pump circuit board


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you have a short in the control wire to condenser..that will blow fuse..or a contactor coil short... that will also blow a fuse..ben sr
To pin point the short I disconnected control wire from the contactor, still fuse was blown. Disconnected capacitor completely, still short. So does it mean that short is in the control (red) wire between circuit board and outside before connecting to connector or somewhere else? Still heat works but no A/C. Good thing I don't need a/c here so I have time to play around and learn. Thanks.
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Old 10-23-2012, 08:52 PM   #21
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Can't locate fuse on heat pump circuit board


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To pin point the short I disconnected control wire from the contactor, still fuse was blown. Disconnected capacitor completely, still short. So does it mean that short is in the control (red) wire between circuit board and outside before connecting to connector or somewhere else? Still heat works but no A/C. Good thing I don't need a/c here so I have time to play around and learn. Thanks.
remove the wire off the y terminial on control board wire off c terminal.....take an ohms meter read between these wires..should be open if no short...
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Old 10-25-2012, 05:16 PM   #22
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Can't locate fuse on heat pump circuit board


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remove the wire off the y terminial on control board wire off c terminal.....take an ohms meter read between these wires..should be open if no short...

Removed Y terminal and C terminal and checked ohms on multimeter. Reading stops at 00
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Old 10-26-2012, 06:10 AM   #23
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Can't locate fuse on heat pump circuit board


I still trying to fix a/c issue. Heat works fine, A/C does not work. I have installed 3V line fuse between control wire to transformer. As I turn A/C on from thermostat fuse is blown. WIres from the control board to the outside unit seems to be good. I have been able to start the a/c motor by
direct contacts. I am stuck and need help to fix this issue. Also I have checked resistance with ohm setting with multimeter on the wires outside
unit. It starts with numbers and stops at 0
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Old 10-26-2012, 03:08 PM   #24
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Can't locate fuse on heat pump circuit board


check the contactor coil on the condenser. you should get some ohms. looks like the coil is short. Disconnect the wires.
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Old 10-26-2012, 03:40 PM   #25
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Can't locate fuse on heat pump circuit board


Disconnect the wires for the A/C from the furnace control board. Then turn power back on to furnace and set thermostat to Cool and set the temp below the room temp. See if fuse blows. If so, its in the wires from the stat to the furnace. If the fuse doesn't blow. then disconnect the wires from the A/C and connect the wires back to teh furnace. See if the fuse blows. If not, its probably the contactors coil. If it blows with just the wires connected, then its in the wires.
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Old 10-26-2012, 04:11 PM   #26
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Can't locate fuse on heat pump circuit board


Nothing to contribute.....except thanks to the good advice you guys are giving the OP.....especially about the fuse.....

It eludes me as to why they would not install one inline with the transformer in the first place. Good advice for anyone to do the same....fuses are cheaper than transformers.
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Old 10-26-2012, 04:16 PM   #27
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Can't locate fuse on heat pump circuit board


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Nothing to contribute.....except thanks to the good advice you guys are giving the OP.....especially about the fuse.....

It eludes me as to why they would not install one inline with the transformer in the first place. Good advice for anyone to do the same....fuses are cheaper than transformers.
cause it doesn't save the manufacturer any money, nor does it make them any money.

Newer furnaces have fuses on the board. because it cost them money when someone returns a board under warranty because there was no fuse.
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Old 10-27-2012, 01:59 PM   #28
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Can't locate fuse on heat pump circuit board


Got some progress. On the heat pump circuit board, two wires Red (joined with yellow from TT) and white are going to outside unit. I separated yellow from the red and turned on A/C. Fuse did not blow and fan started running. Earlier only heat was working, now heat and fan in A/C mode are working. Red and white wires are connected on the circuit board and outside unit but yellow is the only one disconnected. So does this situation telling something? Thanks you all for the great education I am getting from this forum.
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Old 10-27-2012, 03:38 PM   #29
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Can't locate fuse on heat pump circuit board


Short may be in red wire to white wire, or the contactor coil.
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Old 10-28-2012, 07:53 AM   #30
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Can't locate fuse on heat pump circuit board


Is there any possibility of circuit board being short?

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