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View Full Version : My Ranco is acting stupid


toothybugs
04/14/2016, 05:25 AM
It's reading high. Very high - 87 to 93. Consequently my heaters aren't getting kicked on and my tank is running at 75-76, which has been verified by both feel and two other thermometers. I have the probe suspended halfway down its length at the surface of the central portion of my sump so it's not getting splashed though it has been dunked a couple times in days past. The main box of the unit is several feet away from the tank and stand and has never come close to where salt spray may get in to it. It's also not heat build in the sump because I have a fan and an open front and back.

Any ideas what I can do or what's up?

Bent
04/14/2016, 06:24 AM
How long have you had it?

Did you cover the probe? It isn't waterproof.

toothybugs
04/14/2016, 06:31 AM
About 5 months. The probe on mine is sealed off.

TONY_C
04/14/2016, 06:54 AM
Shut the unit off. Open up the controller and disconnect the sensor wires. Using an Ohmmeter, check the resistance of the sensor. If you say your tank is a verified 75-77 degrees, your resistance reading on the sensor should be about 30,000 ohms or 30Kohms

From the Ranco spec sheet:

50 F is 59,700 ohms
68 F is 37,470 ohms
77 F is 30,000 ohms
86 F is 24,170 ohms

If the sensor is reading the wrong resistance for the temperature, replace the sensor. If the sensor is correct, you most likely need a new controller.

Here's the link to the instruction sheet, it's the second pdf on the webpage. http://www.etcsupply.com/ranco-etc111000000-digital-temperature-controller-p-86.html