24 volt circuit blowing fuses

[denrayr]

Ive been continually working on an old goodman unit in a trailor home. Last summer the 3 amp fuse on the board blew. I went out and ohmed out all of the low voltage wires and found no short, so i replaced the fuse. The fuse blew instantly, so I removed the low voltage loads from the board and tried again. The fuse blew again, so I replaced the board and all was well. A month later they called back with the same problem. This time i was getting weird readings on the thermostat wires. I replaced the wiring to the thermostat and the thermostat itself. As a precaustion i also replaced the wiring to the condensing unit. A month later the fuse blew again. This time i didnt have time to do any troubleshooting, so i replaced the fuse and left. The unit has worked fine for about 8 months, and the fuse blew again. The secondary windings on the transformer are a bit low so i replaced it, but im not convinced that was the problem. These people have an ozone air purifier in the same room as the air handler. As soon as you walk in the room with the air handler the smell of ozone is overpowering. Im wondering if this ozone is reacting with the dust or something and causing shorts between the traces on the board. Is this a possible answer?

[RegUS_PatOff]

what's the Transformer rated at ?

you could measure the normal current draw (in series with the Fuse)

it may be at or near the Fuse's 3A limit, but with some added accessories, may, at times, be higher

and/or if the Transformer can handle it or may need to upgrade.

 

[denrayr]

it was a 40va transformer. After replacing it the unit is fine. I didn't measure the current draw because when it shorting the fuse blows instantly with a flash.