Temperature controller problem...

[t316]

I have an Aqua Medic temperature controller with a 500 watt titanium heater. Never had a problem until now. It's like it has "reset" itself or something and is reading in the upper 90's to low 100's. Fortunately, my chiller knows the correct temp is 80, so the chiller would still kick in if things need cooling down, but obviously the heater will not come on if temps dropped, since the heater is controlled by this malfunctioning controller. Everything looks fine on, and I have cleaned off the sensor. And it doesn't look like the sensor comes off where you could just replace that. And it's not the heater, I have plugged it into a seperate outlet and it heats up in seconds.
Any thoughts before I scrap it and have to buy a whole new controller?

 

[scsinet]

IMO, scrap it.
Once you feel there is even a chance that you can't trust a temperature controller, it's time to junk it.
More than likely, something in the sensor circuit has failed. Seawater incursion into the sensor bulb would be my guess, but it could also be something in the internals such as the precision voltage source, etc. Although it may simply read, say 10 degrees high, the slew may be off. Slew is the rate of rise per se, so while 80 may read as 90, 85 may read as 100, 90 as 130, etc etc. So it's not simply a matter of learning to "subtract x from what it reads to get the actual temp."
I'd strongly push the Ranco controllers. They are the de-facto best there is, and if I'm not mistaken, their sensors are replaceable.

 

[t316]

Okay, thanks SCSI. I'll look into the Ranco. Maybe I can find one where I can still use this titanium heater. It can't be used alone since it doesn't have a dial or anything. But if I can buy a controller with sensor only, maybe I can salvage part of this setup, and I scrap the rest. I don't feel comfortable with it either, just thought I'd check to see if somebody new something about these things that I don't. But I don't see any way to reset it or adjust it.