More than likely you have a short in the fan motor. will require replacement.
Don't forget the wiring in this circuit could be faulty, the fan switch, even the fan relay can cause a short.
Need to know which 20 Amp fuse is blowing.
This is the starter fuse I am talking about. It doesn't blow every time. It might go weeks before it blows again.
A current greater than 5 amps; check for short circuits.
Short in the speed control switch or the wiring.
It will draw over 18 amps and will blow a 15 amp fuse.
a massive overload of that particular circuit... cheers Aussie charlie..........
What Causes Any Fuse to "Blow?"The cause is what fuses were invented and are used for:to detect and protect against SHORT CIRCUIT conditions, and /or CIRCUIT OVERLOAD conditions.
Probably a short to ground.
Yes, as long as it doesn't blow. You can always go lower with a fuse, but not higher.
The starter is failing.
No. You will blow the fuse or trip the breaker at the main panel.
If you do that the likelihood is that you will blow the 3A fuse quickly. There is a reason why the current fuse is what it is, because it is expecting currents around 80% of 13 A or around 10 A.