After a good, long while of constant, reliable use, the timer on my Kenmore 70 Series dryer stopped advancing, requiring a manual stop.

I purchased a used timer unit on another site. The part number for the original timer is 8299784, and the used unit was a 3976577 timer, which I'd read was the correct replacement part.

I replaced the timer making sure to place all wires in their correct locations, plugged it back in and fired it up. The timer advanced and all was well.

Fast-forward 24 hours to laundry day and 20 minutes into its very first Timed Dry (not auto) cycle with an actual load, it trips the breaker. (Admittedly I thought the timer caused the problem so I put the old one back in, it didn't start, and then finally a while later thought to check the breaker. I reinstalled the used unit.)

Now this used unit will not advance, just like the original timer. The dryer still heats and works fine - it just won't shut off on its own because the timer won't advance. The schematic is taped inside, but I am not an engineer and A. don't understand the schematic and B. have no measurement tools for troubleshooting.

Just a couple more bits of info: I have only ever used the Timed Dry function to test the timer. The used timer has a black wire instead of a brown wire for the timer motor.

How many different 70 series dryers are there? I can't see the model, # anymore on this unit. But it needs a timer.