Pump not switching off

I've read through a number of posts, and this seems to be a common problem but multiple possible causes.
I have a Jandy Aqualink RS4 that is about 16 years old.
I replaced the pump 3 weeks ago and now it won't cut off normally. I have to switch it on and off at the main breaker and have been doing this for 3 weeks. I hear a clicking sound when I switch from normal to service mode on the control panel. All the lights on the control panel and the inside panel work properly.
I also replaced the water temp sensor and wire since I thought that might be the problem, but was not.
I recall the pool guy saying he thought it was a relay, but I see some earlier posts that say it may be the breaker.
I did notice the breaker was half tripped before I replaced the pump. So before I spend $75 for a relay, I'd like to hear from others if it is likely the relay, the fuse(s), or something else.


TFP Expert
Mar 2, 2011
Probably the relay. If you get overcurrent, you can get a spark where the contacts meet and the contacts get arc welded together.