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-etc11...ller-p-86.html

04/14/2016, 05:25 AM	#1
toothybugs In Memoriam Join Date: Aug 2013 Location: The smallest county in Illinois Posts: 1,986	My Ranco is acting stupid 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?

04/14/2016, 06:24 AM	#2
Bent I got nothin' Join Date: Nov 2004 Location: The anals Posts: 6,420	How long have you had it? Did you cover the probe? It isn't waterproof. __________________ Quitters never lose. [QUOTE=CStrickland]Who gets mad at a starfish?[/QUOTE] Current Tank Info: 75g DT, 30G refugium, 10g chaeto tank, 50g stock tank basement sump

04/14/2016, 06:54 AM	#4
TONY_C Registered Member Join Date: Feb 2016 Location: N. Bellmore, Long Island, NY Posts: 92	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-etc11...ller-p-86.html Last edited by TONY_C; 04/14/2016 at 06:57 AM. Reason: added weblink

04/14/2016, 06:31 AM	#3
toothybugs In Memoriam Join Date: Aug 2013 Location: The smallest county in Illinois Posts: 1,986	About 5 months. The probe on mine is sealed off.