Pentair MasterTemp 300 - gets power but no error codes

[ckhorne]

I've read through the Mastertemp further reading on here, and I've worked through the service manual, but I'm not sure what my next step is.

I have an old MasterTemp 300. No changes to my system in many months- everything has been working fine, including the heater. Suddenly it doesn't work. My suspicion is that its related to a large storm we had come through recently - several neighbors had to replace electronics from lightning strikes.

• Heater gets power. I can test the 24VAC transformer; it's doing its thing, but I do get a solid 27VAC.
• When the main PCB gets power, all LEDs turn on for a second, and then off. Afterwards, no LEDs ever light.
• The LCD doesn't turn on at all
• The fuse is confirmed to be good

Its been ~4 years since I wired up the heater to my aqualink, so I'd have to go digging for the details. I have a Jandy Aqualink RS; the Jandy controls the heater directly, sending the heat command, rather than the heater itself acting as the thermostat.

I know I can replace the main PCB and/or the transformer if needed.... I'm just not sure what to test or what steps to take next without just throwing money at it...

Any help would be appreciated.

 

[ajw22]

Before you do anything else go to the firemans switch connection in the heater and disconnect the control cable and connect the wires at the heater together to put it in local control.

See if the control panel lights up.

If the heater is under local control and the PCB is getting 24V and the display does not light up then the PCB is bad. No diagnostics you can do on it other then check it is getting power.

 

[ckhorne]

That's a negative, Ghost Rider.

I plugged in the fireman's switch, and noted the same behavior - all LED's light up for a second and go off (and stay off). I verified that I was getting 24VAC through the test.

So... I guess I get to replace my PCB.

 

[ajw22]

Did you press POOL ON or SPA ON?

 

[ajw22]

You checked you have 24V AC at the power connector plugged into the PCB?

 

[ckhorne]

Well, I feel like an idiot now that you pointed it out- I assumed the fireman’s switch /jumper would force heat on….

With the fireman’s switch in place, I can operate both pool and spa modes using the LCD.

So I hooked everything back to the control wires as before. This time, after I turned on the heater from the aqualink, I also turned on the heater via the button. And it worked. Then over the next 30 mins, I went though all the normal operating modes and it all seemed to work fine…


I’ve had this setup for 4 years and never had to turn the heater on manually to get things started, even after power outages….

 

[ajw22]

The MasterTemp will start with the Fireman's Switch in whatever mode it was shutdown.

If it was ON then the MasterTemp will restart ON without any button pushing.

If the MasterTemp is put OFF for any reason then the MasterTemp will restart OFF with the Fireman's Switch and you need to press POOL ON or SPA ON after the heater is powered with the Fireman's Switch.

 

[ckhorne]

I presume the aqualink is acting just like the fireman’s switch in normal operation, shorting out the two connections when the heater would be on?

If so, then the same logic should hold- the unit should turn on again if the last mode it was in was on, right?

 

[ajw22]

I presume the aqualink is acting just like the fireman’s switch in normal operation, shorting out the two connections when the heater would be on?

If so, then the same logic should hold- the unit should turn on again if the last mode it was in was on, right?

Yes & Yes.

 

[ckhorne]

Then it appears I just never turned the dang thing on again at the heater for everything to work.

Thanks for your help!