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V50 Chemical Temperature Problem


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Hello all, can anyone help me.

CD tank on my V50 will not stay 37.8c that I have it set to.  It fluctuates between 36.5 and 38.5, sometimes higher and gives a solution temperature error.  Sometimes it will stay at the right temperature for 10-20 mins, then it just goes up and down and doesn't steady itself.

I initally thought this was a circulation error so I have drained the tank, thoroughly cleaned it, blowing water through all the pipework, changed the chemical filter, I even took both circulation pumps off the machine, opened them up and made sure everything was clear.

Put the machine back together with fresh chemistry and still the same problem occurs.  I have checked the temperature with a digital thermometer and it matches what the V50 says, so I know the thermostat isn't at fault.  I know the circulation pumps are working because if you manually turn them on and off in output checks menu, you can see the chemical moving in the compartment where the filter goes.

What I don't understand is the speed it can go from 37.8 to 38.5, 5-10 seconds.  But when it is warming up in the morning it takes a lot longer than that to cover 0.7c.

Does anybody know what else I can check??

Sorry for such a long post, just wanted to give you as much detail as possible.

Many thanks

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Hi, thank you for your reply.

I have cleaned both circulation pumps and they work fine.  I don't think it is the relay because it does stop heating.  I thought if the relay was fault it would just keep heating and not stop.

It's the speed it gets from 37.8 to 38.5 that worries me, the heating element isn't capable of heating at this speed which indicates a circulation or thermostat problem but I think I have checked everything.  Could there be anything else?


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It's still worth actually removing the sparge pipe, and cleaning each hole with a paper clip etc, there are a lot of holes, so it may look ok when inside the machine, but 50% of the holes could be blocked.

Other things you can check are the pipes going to the top of the pumps are not squashed flat at any point.

Check the impellers inside both pumps spin freely on the shaft, there is often a build up of silver on the shaft causing the impeller to not spin freely, which will cause a reduction in the circulation.

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Just to update,

Took the board off and instantly saw the problem.  SSR relay 1 has a black spot on one of the pins, looks like a fault has occurred.  I have put a new board in and just waiting for the chemical to heat, hopefully not over heat !!

Thank you to SAIT for solving the problem, my next question is:  where can I buy a replacement relay to solder onto this board?  Noritsu want £1000 for a new board and do not sell the seperate components.

Thank you to all that helped.

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Normally when the SSR has totally gone the temperature will keep rising and rising until the safety stat cuts the power to the heater (normally around 40oC)

Although I have had a faulty SSR that would only partially switch off, it was letting through 100V which most of the time did not cause a problem, I guess the power leak was about the same as what the machine needed to keep the tank at the correct temperature!

The tell tale sign of a faulty SSR is the colour of the SSR goes slightly brownish. The CD heater is SSR1

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