3amp fuse on circuit board keeps blowing mr heater big max model

Replace the circuit board, or call a technician to do it. No one repairs field replaceable subassemblies any more.

Check 24 volt wiring That would be wiring from your thermostat to heater

Short circuited component/s at its internal circuit board.
http://electronicshelponline.blogspot.com/

it should still be under warranty.

That unit has a thermostat I believe and 12 or 24 volts to power it. The 3 amps tells me it may be either line or low voltage, see manual. the fuse blows due to a short in the control circuit, a transformer if low voltage.

disconnect the thernostat wires from the control board. Put a jumper wire between R & G put door back on and turn on power. Blower motor
should run, if it blows the fuse then you have a direct short between R &
G at the board. Do this with R and W(heat) and R & Y(cool).

By disconnecting the thermostat wires and reinserting them make sure that they do not touch when inserted into each terminal. If it still blows
that little 3amp fuse when jumpering between each sequence as mentioned above, then I think your board is bad. When Jumpering out the Y terminal you will have to have the AC wires still hooked up. If it
blows the fuse in that sequence. Disconnect the wires out at the condensor.

You mat have a bad contactor at the outdoor unit.

in the printer there is a power supply board.there is a same type of 3amp fuse on the power supply board.if there is any kind of overheating in the power then the fuse in the plug and fuse on the power supply board blows out.in some cases only fuse on power supply board blows out.this fuse is placed on the board for safety reasons.because in the older model printers when this short circuit problem was happening at that time whole board used to blow out.so in the new model of printer a fuse is placed on the board ,so if any overheating or any power outage or any short circuit occurs.the fuse blows out instead of whole power supply board. You just need to replace the fuse on the power supply board by disassembling the printer.the power supply board is the green color square shaped board.its the board to which your power wire of printer is connected. the fuse is available at any local electric hardware shop.its not any special kind of fuse. This will help. Thanks please keep updated. please please do rate the solution positively .thank you for using fixya

You have a low voltage short. A lot of low voltage shorts come from the wires that go out to the outdoor unit. Go outside and inspect those wires and that they are in good condition. Also check for any splices in those wires that they haven't degraded in any way. This is the only thing that will blow the fuse. That's why it's only 3 amps and based on the size of your fuse, it's a gas fired unit right? Have a great day!

Mr. Larry (guru?)
The thermal fuse is just that It doesn't protect the circuit from over current although it certainly can open in that case. It is there to protect the board from overheating , thus the term thermal. The dishwasher could be allowing the water to heat too hot or the water heater in the home is turned up too much. The heater could also be shorted to case thus allowing it to be on even though the control is not calling for it especially if the polarity is incorrect to the dishwasher or the relay on the board could be welded closed so that the heater can't turn off even though the thermostat is satisfied. The best thing is to get a person who can check these things. You don't necessarily need to change the board with a fuse. I have changed many fuses with no other problems and verified that the machine was still working years later. sometimes the fuse just blows!

Hi,

when a fuse blows, its telling you that theres a fault. this could be a loose or broken wire.
or alternatively, the fuse rating is too low. you could check the wires are tight. and also possibly try fitting a 5 amp fuse. check first that the fuse is rated correctly for the appliance. usually 3-5 or 13 Amps.

Mike @ compurepair.