timer stops but does not start back up

Question

My timer does not start up at the desired time that I set it for. The pump shuts off at the desired time, but it appears to not move forward at that point.

Answer 1

Your question does not have enough detail to give a certain answer, but I will WAG on a couple of likely problems...

1. You have a mechanical timer with a broken part or parts.

1a. Mechanical timers commonly have a tooth that engages a cog to switch the unit on or off. If the tooth is worn or broken (or the cog), it will not switch. The problem is especially common on Intermatic-style timers (like this) that have little plastic parts (or 'pegs') that you can remove and insert to set the on/off times. Alternately, some other part of the switch mechanism may be worn or broken or jammed.

Troubleshoot this by comparing the removable on/off time setting parts (if your timer has them), or just turn the time dial manually and observe it turning on and off (or not). You may be able to get it going with some cleaning, or find new setting pegs. (If you spray something in there, use the non-flammable kind, not WD-40! Find Lectra-Clean or similar at your favorite home store.) Or, it's a straightforward wiring job to just replace the whole timer.

1b. As commented, the motor that turns the timer may be worn and not producing the necessary torque to activate the switch mechanism. Since the pump is turning off correctly, it seems unlikely the motor has stopped completely. However, the switch may require a different amount of force to turn on vs. off.

There are a number of other possible problems with a mechanical switch, like the contacts may be pitted, burned or otherwise damaged (preventing the pump from starting). If you are getting the idea that mechanical switches have a myriad of possible problems, you are correct. That is not to say that electronic ones do not have problems of their own, just that you have other options.

2. Your pump has a capacitor type induction motor, and the capacitor is bad (or both capacitors are).

An induction motor may have a start capacitor, run capacitor, or both depending on its design. A start capacitor allows the motor to develop the extra torque required to get going when it is stopped, then disconnects via an internal centrifugal switch once it gets up to speed. The run capacitor provides reactive power (electrically, a phase change) so the motor runs efficiently.

If the pump does not start reliably when you turn it on manually, the start capacitor is likely to be the problem. If the run cap is bad the motor may stop while it is running or run slowly/poorly under normal load. Capacitors wear out due to time and heat, and replacing them is a normal part of maintaining equipment with big electric motors. A new capacitor should not cost more than $10-15. So if your pump is more than 5-7 years old you could troubleshoot by just replacing it.