Im doing a retrofit on an older  sharnoa a cnc  machine. I have Dmm Ac servos ess board w/ c62 bob. Im trying to hook my coolant ssr relay up . I can power the pump fine but when I go to shut it down it stays running. The input and load are connected properly . The input is the 4.95v from the ess the load is 220v.
Any suggestions?

If you disconnect the input, the pump stays running??


If yes then the SSR is blown - permanently on is a favourite failure mode for SSR's.

This is a common problem with many manufactures. A quick google search will show that . Once the load triggers the on mechanism/ circut they wont shut off until there is a certain lack of or provided volts. People use different resistors or capacitors to achieve this . Im not savy enough to know.
I have ten new solid state relays . I doubt there all bad.
could be though

https://www.google.com/webhp?sourceid=chrome-instant&rlz=1C1HLDY_enUS731US732&ion=1&espv=2&ie=UTF-8#q=ssr+wont+turn+off

Sounds like you might need a pulldown resistor to ensure the output from the board goes below the threshold voltage of the SSR.

I'm not sure of values here but a 1k resistor between the SSR input and 0v would not do any harm, can't guarantee it will work though

Probably does not apply in this case but...

There are various types of SSR's with the most common type designed to switch the load ON / OFF at the zero crossing point of the a.c. mains waveform - they will not operate correctly with a d.c. load.

Tweakie.

Yes, i read this as an AC 220v pump.

Sounds like the BOB output is not dropping low enough to release the SSR.

OP - can you get your SSR turned on then confirm it WILL stop the pump if the 5v signal is disconnected at the SSR?

As I wrote Im doing a retro fit. One of the older power supply for the 24v AC had a ceramic capacitor the bridges the two -+ sides together . I hooked that power supply up with that capacitor  and boom it works.
I have no clue what capacitor it is because the top of the resistor is laminated in a red wax material .
At least im on the right track.

If it is a red round type of component it's probably a MOV or metal oxide varistor - a type of self resetting shunt that helps prevent voltage spikes.

Glad its moving on