View Full Version : Gravely Promaster 20H Blown Fuse

05-27-2007, 06:35 PM
Fuse between the ampmeter and hot side of the solenoid will burn out after 15-20 minutes of mowing. Then, it will blow a new fuse within minutes if you replace it immediately. Any ideas?

05-27-2007, 07:56 PM
Is the fuse the correct size?

05-27-2007, 09:52 PM
Check the positive power lead (red) on the back of the ignition switch for rust/corrosion. If rusted the contacts inside are most likely burnt/shorted, Replace the switch and red connector.

05-28-2007, 12:24 AM
Also check the fuse holder. If the holder has rust/corrosion it may not hold the fuse tight and cause it it heat which will cause it to blow at a lower amp load than it should. A 20 amp fuse can blow at 10 amps if the fuse gets hot. This is called "cooking". When a fuse cooks it damages the holder even more until it is totally useless.

05-28-2007, 12:58 PM
All connections are rust free. The fuse size was a 20 amp fuse. I bought this mower used, so I'm not sure of the fuse size for sure. I have tried 15, 20, 30 amp fuses. I can't find a wiring diagram for this ZTR mower

Bill Kapaun
05-28-2007, 01:26 PM
Did the 20 & 30 amp fuses take the same amount of time before they blew?
What I'm thinking, is IF they did, it's a heat related issue. Something starts drawing excessive current when it gets hot or something "moves", causing a short. Just what "heat related issue", I don't know.

DOES the ammeter start showing increasing current flow before the fuse blows?

05-28-2007, 05:04 PM
I can't find a wiring diagram for this ZTR mower

If I had full model and serial numbers off this unit there's a good chance I may be able to drum up one.

Does this one have the Kohler or Onan ?

05-29-2007, 08:53 AM
Promaster 20H, s/n 00633259, 60 in. deck, Kohler MV20S (57513)

05-29-2007, 07:09 PM
Here's the wiring diagram.....

You may try by-passing the ammeter by connecting the pink/black and white/black together, I have seen ammeters short out.


05-29-2007, 07:40 PM
Thank for your help. I'll let you know what I find.

03-23-2011, 11:33 PM
Was the ameter the problem?

03-24-2011, 06:54 PM

If your having issues blowing fuses it's easy enough to bypass or test the amp gauge to see if that's the cause.