Most of the time, you only know something is wrong with your lawnmower when it's too late: to prevent damage in the first place, here are some of the major causes of scag clutch failure. 

The scag clutch is not adjusted
Your scag clutch in your mower needs to be adjusted every 500 hours of use, or at least once a year. If this type of electric clutch becomes too loose over time, or if the space between the plates is screwed on too tightly, this inhibits your drive shaft movement, thereby causing warping or vibrating.

Replace your old scag clutch if you notice any damage or bending.

You've used the clutch puller
It might have been an accident, or it might have occurred during an emergency: regardless, if your clutch puller has been pulled, your scag clutch is likely useless since this feature is designed to destroy the clutch as the last resort. 

You'll need to find replacement lawn mower parts before you get your mower back on the grass.

The clutch wire isn't grounded
Your electric clutch relies on clutch wires to dispense between 12 and 14 volts of electricity. Look for tears or fraying in your wires and ensure your second wires are connected to the engine block. If there is any sign of corrosion or rust on the wiring, it's time to replace the wiring before you buy an entirely new clutch replacement. 

If your clutch receives the electricity, but still doesn't work, it's time to get a scag clutch replacement or another type of replacement clutch for your mower. 

Improper belt installation
Mowers require belts to turn the blades. If you have a worn out belt, or if your belt is burnt in one or more places, you may simply need a belt replacement. The resulting changes in speed and deck positions often lead a mower owner to assume there is an issue with their clutch, however, the belt may be the issue. Get the correct belt for your mower and get it properly installed by a service professional. 

Rust build-up
Rust accumulation from a stagnant mower can cause an electric scag to freeze up. If you haven't used your mower for a few months, clean the rust between the plates and engage the clutch a few times to rub away leftover rust. Do this a few times before you seek out replacement clutches.

Before you make hasty decisions to replace your clutch, consider these options to rule out the possibility of clutch failure. When Americans spend nearly $16 billion on lawn care, it's essential you have the working parts to take care of your mower.