My 3 year old (home personal use) precor 9.31 treadmill has started makking a dull continuous clicking noise when the belt starts. The noise appears to be coming from the back end. The noise get reduced when the machine warms up. Any guesses? Could it be the ball bearings in the rear or something similar? Thanks.

SOURCE: ???maximum user weight for Precor 9.45i

Normally most home treadmills are 250-300lb user capacity.
Call Precor with your model # and S/N and they can tell you exactly.

SOURCE: Precor M9.21 Treadmill - Stops under load

This probably did not happened suddenly right? the problem is not the motor however you can easily check the blue capacitor for peace of mind. with the power disconnected, disconnect one side off the capacitor from the top. with a ohm meter put the 2 probes on the cap,you will ear a temporary beep sound from your meter, then reverse your probes on the capacitor and again a temporary sound that mean your capacitor is good and your motor will run OK.

Your problem is more then likely your run belt and bed assembly. When new, these are coated with a wax of some kind for slipping, has you use the machine wax wears off, and so is the belt. You can see a black rubber dust at the rear of the machine. And so resistance increase when pressure is applied on the running belt.

Just behind the on/off switch where the power cord goes in, there is a auto reset 15 amp breaker that trips when too must resistance against the motor increase the amperage over 15amps. At 7 min/m on your speed setting and if the belt is adjusted correctly with nobody on, the motor pull about 6amps, with someone like me 180lbs, the motor pulls an avg of 10amps with a new belt.

If you have a clamp amp meter you can test it yourself.

2 parts you will need to fix this; 50985-101 (bed assembly) and 36355-101 (run belt 17 X 110) This is real easy to install.

make sure these parts are for your machine model # as they did increased the width of their belt over the years

Since 1998 I had to replace these parts 2 times with an average of 3 people using the treadmill every day. This is a good machine and if everything else is good it's worth it. I paid $300 for these parts, i'm sure if you shoppe a little you can do better.

Have a good one

Ben

SOURCE: wax or silicone on my 10+ year old Precor M9.21

Use silicone to lube your treadmill.

SOURCE: Where can I find a Precor 9.21 treadmill motor cover?

Do you know which version of the Precor 9.21 you have? There are a few different versions you can view here. Click on your version to view the parts list and look for "Cover, Motor" or "Motor Cover".

For instance, if you have the 9.21 (AYYZ), the proper motor cover is this part #5019749

However, this part #5005569 is listed as the proper motor cover for the 9.21 (F5), 9.21i (2X), 9.21s (F6), 9.21si (2Y), and a couple others. Make sure you have matched up your exact model number with the motor cover you need so do you not order the wrong part.