Wrong temp sensor reading

[mkelley]

I have an inground pool with the Aqualink with the remote control unit inside the house and solar heating with a sensor that goes to the Aqualink. The Aqualink has it's own pool temp sensor and suddenly it's reporting that the pool is 152 degrees (it isn't ;>). Needless to say (but I'll say it) the solar sensor knows the water up top ain't that warm and isn't turning on, but this isn't as big a deal (I can always work the value manually) as the other sensor not working.

I tried turning the breakers on and off but this didn't do anything -- is this something I will have to call in a pool professional to fix, or is there any chance at all I can do it? (This board has been great in saving me when I had to replace auto valves so I'm keeping my fingers crossed here).

[Titaniumboy]

It appears that the Aqualink temperature sensor is what is known as a "10k thermistor". There are several types of 10k thermistors which read slightly different temperatures, but the basic idea is that the electrical resistance of the thermistor changes as temperature changes. A 10k thermistor will have a resistance of 10,000 ohms at 75 degrees F. For your thermistor to have a reading of 152 deg F would require the resistance to be somewhere between 1700 ohms and 2400 ohms per this link http://www.veris.com/file_uploads/RTD_thermistor%20graph_i0l2.pdf

Although the thermistor is probably broken, you could try swapping the wires of two different temperature sensors where they connect to the Aqualink circuit board and see if the problem seems to move with the swapped temperature sensor (means the temperature sensor is bad) or stays put (means the temperature input on the Aqualink circuit board is bad).

Here is one person's fix for the Aqualink temperature sensor, but it should work for any system if it is utilizing 10k thermistors.
http://www.mycal.net/?cpath=/Projects/pool_projects/&id=387&action=9

Good luck. Let us know what you find and what you end up doing.

Titaniumboy

[mkelley]

Thanks for the info.

I guess what I was thinking about was less how to jerry-rig a workaround then just how to replace the sensor myself. As it stands I don't know where it is (and that article doesn't really help along those lines) so I'd have to just call and tell them "fix it" which I'm sure will cost more than if I could replace it myself.

But if it's too complicated to replace then I'll just bite the bullet and do it -- I don't know where I'd get the part, either, so maybe that will be what I have to do.

[waste]

If you have another one, or can get one, the replacement is a lot easier than the actuator valves;) Sorry to hear that your aqaulink is giving you more trouble:( . I saw this yesterday, but titanuimboy's response was so good that I had nothing to add (WELCOME to the forum Titaniumboy!!!:) - great first post!!). What I really liked was the suggestion to switch out 2 of the sensors - it's quick, dirty and easy. Open the box, remove the 3 screws to remove the cover plate. On the left side is the area to run all of the wires through (actuators and thermistors) - follow the 3 beige wires to where they are attached - switch out the solar and the air and see what the unit thinks the air temp is. (you'll need a very small screwdriver to disconnect and reconnect the wires - I'd advise putting a piece of tape on the solar wire so you don't get them confused while changing them around) If, as suspected, the solar thermistor is bad, pull the wire out of the bottom of the unit and trace it back to the thermistor itself - you've now found it. Once you have a replacement thermistor and know where it goes, you'll see just how easy the change-out is going to be. It's held in place by a clamp, loosen the clamp enough to remove the bad one and simply put the new one in it's place, run the wire back to the unit and attach the new wire where the old one was -- simplicity itself!:p Just be sure that the solar isn't under pressure when you make the change-out.

I can assure you that this will be easier than the actuator - waste

[Titaniumboy]

waste,

Thanks for the nice welcome. I have been posting as "Titanium" on - ahem - another pool message board. I started posting there only because I had misplaced my login information for PoolForum.

My first, and so far only, pool test kit was purchased from Ben last summer. I first learned about BBB on this site and am really sad the way things have turned out with regards to Ben.

Titaniumboy

[Titaniumboy]

Here is another possibility. Here is a Jandy temperature sensor repair kit being sold on eBay.

http://cgi.ebay.com/Jandy-pool-temperature-sensor-repair-kit-for-7790-7784_W0QQitemZ290169410721QQihZ019QQcategoryZ3243Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem

Titaniumboy