Here are a few of the most common spa or pool pump timer problems and troubleshooting tips:
Of course the most common problem is the timeclock will not turn on pump:
1 A)Is there power to timeclock?....check the breaker-on a 230 volt system there will be two breakers to check-even if they look like they are not tripped,reset them anyway. On most mechanical timeclocks there is a window to see if timeclock gears are turning (photo above,oval window showing black gears)
1 B)Are you getting 120 voltage on each of the contacts but not 240 together and its a 240 timer/pump? The way to double check is to disconnect both line (power from breaker) wires from timeclock and check each individually with voltmeter to ground. The reason you must disconnect wires is voltage will travel from one side of the clock motor winding or pump motor winding to the other contact - the nasty thing about this is if you put the voltmeter across the contacts (while they are still connected to timeclock) you will get a false zero voltage when in fact one wire is hot so be careful.
2)If you reset breakers,and gears are still not turning,then perhaps the clock portion of your timer is burned out. Check with volt meter to see if you have power on the "line" connections.
3)There is power coming in to timeclock,gears to clock motor are turning,but when turned on no power to pump: sometimes ants or other insects are crawling on timeclock relays when power comes on and they get electrocuted all at once,creating a barrier of ants in between the electrical connections...clean the contacts on the back of timeclock(WITH POWER OFF EINSTEIN!)
4)Timer comes on manually but not automatically or comes on automatically but does not go off:either the on or off tripper is missing or perhaps bent....also,try lubricating the switch mechanism...one pool owner in Boston tried WD-40 with no success but had better luck with a heavier lubricating oil.
5)Timeclock does not keep time:clock portion of timeclock is burnt out or gears to clock are stripped-the clock portion is available as a separate item.
6)When timeclock comes on,breakers trip:could be timeclock contacts are burnt out. The contacts on back of timeclock should be smooth and shiny...if they are burnt and/or pitted,change the timeclock. Also check wiring connections at timeclock-a loose connection can cause the breakers to trip.If the contacts and connections look good,perhaps the pump is shutting off breaker-more on pump motor problems in the link at bottom of page.
Below you can see new contacts in good condition(tips on thin brass metal) Also,you will notice two white wires going to clock portion of switch which can be bought separately if you are on a budget-but I usually replace the whole unit if I am going through all the trouble to rewire unit.