Fujimoto CP31 heater not working

[yelmarb]

I've recently purchased a barely used Fujimoto CP31 but despite it's immaculate condition, tank number 2 isn't heating up (tanks 1 and 3 do heat normally).

The number 2 control pot LED does glow so it knows that the tank isn't up to temperature, which I gather means that the temperature sensor is okay.

Has anyone had a similar issue that they've managed to fix?

 

[koraks]

Verify the heater actually gets power. Check continuity on the heater. Check if there's a thermal safety switch and if that shows continuity. If the heater element is switched by a relay, verify that it turns on/off, and verify the relay contacts show continuity. At this point you should have a decent idea of where to look.

If you don't know how to probe the things I mentioned, try swapping the heaters of tank 1 & tank 2, then see which one(s) turn(s) on. This will also tell you whether you're looking at a problem located in the heater itself (and any thermal protection it may have) or the switching circuitry.

 

[yelmarb]

Thank you for the reply @koraks. I did swap the thermostats around and it didn't solve the problem, so they're fine. However, to test if there is power going to the heater I obviously need to turn it on. How do you do this safely without water in the processor?

Any ideas on how to find the heating relay or thermal safety switch?

Pic attached shows the heater bar with the spade terminals off as I'm about to swap them around.

 

[koraks]

However, to test if there is power going to the heater I obviously need to turn it on. How do you do this safely without water in the processor?

Disconnect the heaters, or find a way to have water in there while testing (work with the unit upright and ensure access to the bottom), or be very fast and turn it off again before things get hot (relying on thermal inertia of the heater itself). Each option has its pros & cons.

Any ideas on how to find the heating relay or thermal safety switch?

Visual inspection combined with probing around with a continuity meter.

Ask a friend who's well versed in electronics repairs, maybe?