Fluctuating temps. - Troubleshooting advice needed

I have brewed around 30 batches with my electric setup (thanks for all the help found here).

I had some weird small temp fluctuations on the last batch but didn't worry about it.

Today I brewed and with the PID set at 152 degrees the temp started at 80 (normal for Texas) and as it was going up it just went berserk. I showed -6, 165, 343, etc. It just kept bouncing around and apparently the PID told the element to stay on. By the time I retrieved my other thermometer and checked it the temp was 155 but the PID showed 165 and pretty much stayed at 165 even though my Thermopen showed 155 degrees. I ended up shutting the power off to the PID and the element.

After turning it back on to get a boil going, it seemed to work just fine. But that makes 2 batches with these temp swings and unreliable temp readings.

I checked all the connections to the temp probe and in my control panel and they are all sound.

So how to I troubleshoot this? Do I just order a new cable, and temp probe and swap them out one at a time? Could it be the PID?

Thanks in advance.

Some temperature probes are not really water tight. So some omount of liquid can get in IDE. And its causing wrong temperature reading.

My temp probe is the waterproof type and is in a tee with the drain valve. There's no liquid in the connectors (I checked) and the cable nor the control panel has not been wet either.

I'll keep looking....

Ray, I use induction and my electronic thermometers are flaky. I called Thermoworks and they were very nice, but they don't sell anything that works in strong fields.

I use analog thermometers now, or power down the heating to take a reading. You might check for an EMI problem due to some sort of grounding or shield failure.

Alternately, you could try slapping it around.

My PID failed and will no longer shut off the element when the temp is reached. I have ordered a new PID to replace the bad one. Sounds like you may have a similar issue?

The TC may be gounding. Does it just do it when the element is on?

dcarter said:

My PID failed and will no longer shut off the element when the temp is reached. I have ordered a new PID to replace the bad one.

Click to expand...

Are you sure about PID failure? More likely you have a failed SSR.

I would check your TC connections too. these things change resistance with change in temp. if you have a bad connection (even a little) it will vary resistance enough to reek havok on the PID.

SOLVED! I ordered a new PID, therm probe and cable with the idea of swapping them out one at a time (worse case means I have some spare parts). I had ohmed out the cable and the connectors in the panel and they were fine. I then put one end on the cable in my small vise, connected the ohmmeter and gave the connector a lot of twisting and bending, thinking there might be a broken wire just beyond the strain relief.

On one end of the shielded cable I noticed the meter would 'blink' while homing one connection. The reading would never change from about .5 ohms but on one wire it would blink and only while twisting the connection. A close inspection showed that one of the connectors looked dull compared to the others. A classic sign of a cold solder joint. I heated the joint and added a bit of solder. Problem solved!

This was on a purchased cable (not one I made). The shielded cable going from the panel to the kettle. A PITA to find but a simple fix.

Thanks for the suggestions here.





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Brumateur said:

Are you sure about PID failure? More likely you have a failed SSR.

Click to expand...

Im not certain, but the "on" light stays on past when the setpoint should have forced a shutdown. I have the new PID with step mash upgrade so I'll update when I confirm.