ProForm City T7 Temporarily Stalls Under Load

I have a ProForm City T7 that started having issues just after the one year warranty expired. In short, it runs fine if nobody is physically on the belt using it, but as soon as there is notable load, it will eventually stall such that my weight alone is enough to stop the belt entirely. Stepping off the belt will cause the belt to spin freely again, at the specified speed... but it will immediately stall/stop when weight is put back on. I can "fix" it by either pausing the program for 10 seconds or letting it "spin" for 20-odd seconds. Both will result in the treadmill resuming its program like nothing happened -- until it does it again, 30 seconds to a minute later.

Some facts. This has a 2.75HP Model 3200 motor and the MC1648DLS controller. The controller has the single red LED for diagnostics and, indeed, it blinks rapidly during normal use and drops to the 1-pulse-per-second mode when it is "stalled". I discovered that that sequence means "foldback" mode where it is detecting too much current and so it limits the output temporarily. Yes, that fits what is happening.

I put a real-time watt meter on the treadmill and through iterative testing, discovered that it goes into foldback mode when the current draw exceeds 500W -- the more current, the faster is trips. The treadmill practically sips current when there is no load -- even 10 mph (much too fast for me) uses only around 400W and the lower speeds are typically in the 100-150W territory. When I put my 180lb weight on it, though, the current draw immediately spikes. Even 2mph with my walking on it uses 600W and 4mph uses over 1050W.

Putting it all together, if I set a speed of 4mph and walk on it, the LED blinks rapidly and the current is at 1050W. After 30 seconds or so, the LED switches to "foldback" mode 1-pulse-per-second; the current draw drops to 150W; and the belt stops under my weight. If I get off the belt, it speeds back up to 4mph; the current stays at 150W; and the LED remains in "foldback" mode. After 20 seconds or so, the LED switches back to "run" mode of rapid blinking and now if I get back on, it will stay at 4mph with 1050W... for another 30 seconds, until it inevitably happens again.

Might be worth noting that the Model 3200 motor has a continuous duty rating of 1492W, so even my 4mph spike doesn't touch that. Still, I get that those are probably high numbers since 4mph isn't even half the max capability and it's already 70% of the max continuous duty rating.

On the topic of the belt, then -- I have been continuously incrementally tightening the belt over the past year. This is because it starts "slipping" very frequently when I don't and that's both very disconcerting and potentially dangerous, when walking fast. I only tightened it each time just enough so that it stops slipping. I have since loosened the belt enough that it does slip a decent bit, but the high current draw and stalling remains. I also bought some treadmill belt lubricant and have applied a goodly amount to under the belt. That doesn't seem to have done anything.

I'm not sure what to investigate next. Is there a standard set of diagnostic steps that should be taken at this stage?


  • This is a failed motor controller. if you can get me the specific model number I should be able to get you a link for the replacement.
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