I have a Craftsman riding lawn mower (DYT 4000) that is about 4 years old and when I tried to start it up this Spring, it had a dead battery. My son replaced the battery but he hooked up the negative cable to the positive terminal and positive cable to the negative terminal, of course it wouldn't start. I reinstalled it correctly and it starts with no problem, but when I engage the blades, it blows the 20 amp fuse and sometimes the engine dies immediately and sometimes it keeps running for a minute, but the blades never start rotating. I hope somebody has some idea on why this would be. I hope the entire electrical system isn't fried.

Thanks.

Bret Remington, May 2008

There is an electric clutch which is attached to the crankshaft (under the drive pulley belt) which when engaged provides power to the mower.

But before you get into that, with the mower off and the key removed, check under the mower deck and see if there is anything obstructing the blades.

Also, carefully turn the blades to determine if there is any resistance there (the blades may turn with some drag. Problems will be apparent at this point as the blades will not turn at all.

If blades will l not turn, there could be a brake on the mower deck that stops the blades when the deck is disengaged. If this is the case, then the deck needs service.

Once mechanical issues have been eliminated, the electrical issues can be investigated.

It is possible that the electromagnetic coils are damaged in the clutch and are creating a "dead short".

One way to check would be to use "jumper wires" with an inline 20A fuse, and hook the clutch up to 12V DC (to the battery) or another 12V DC source.

Disconnect the clutch wiring from the tractor (two wires in one connector).

You should be able to rotate the pulley (the paret which the mower belt is on) freely at this point.

Attach your jumpers to the two terminals on the clutch, and then to the 12V DC (battery or other source).

If you hear a click and the clutch will no longer turn with the power attached, the clutch is good.

If the fuse blows, the clutch is shot.

If the clutch is shot, fortunately it is pretty easy to replace.

Before getting started, make sure you remember the proper routing for belt.

A photo can save a lot of trouble later. If no camera, draw a picture, and or label the parts for reassembly later.

Now, back to the work

There are a couple of springs which hold the clutch from spinning when engaged which need to be removed. Either from the clutch or the frame.

The bolt passing through the clutch to the crankshaft then needs to be removed.

At this point, the clutch will drop away freely (or should).

The drive pulley will likely "hang" on the crank due to the drive belt, but it will probably fall as well.

To replace, reverse this process, and use a torque wrench to tighten the crank bolt to the mfg. recommended torque.

Jim, May 2009