Bob M Posted March 31, 2011 Report Share Posted March 31, 2011 I have a Jandy LT heater that has been working fine. But now when using the spa which we set to 100-101, the heater shuts off when it reaches 98. It will try to start 2 more times, blower starts, ignitor lites, but gas doesnt come on. There is no error condition indicated. When the spa cools to about 95-96 the heater will come on and go up to 98 again and then shut off. The temp sensor is accurate and the limits are set to max at 104. Anybody ever seen this problem before. Thnaks, Quote Link to comment Share on other sites More sharing options...
Poolmech Posted March 31, 2011 Report Share Posted March 31, 2011 Are there dual thermostats on the heater? If so, switch to the other thermostat and make sure it's turned all the way up. If it heats completely, it's a bad thermostat. Quote Link to comment Share on other sites More sharing options...
Bob M Posted March 31, 2011 Author Report Share Posted March 31, 2011 Are there dual thermostats on the heater? If so, switch to the other thermostat and make sure it's turned all the way up. If it heats completely, it's a bad thermostat. Yes, dual thermostats, both are turned all the way up. Does the same thing on both. Quote Link to comment Share on other sites More sharing options...
Pool Clown Posted March 31, 2011 Report Share Posted March 31, 2011 You mentioned that the sensor is good. What was the resistance reading across the sensor? Quote Link to comment Share on other sites More sharing options...
Pool Clown Posted March 31, 2011 Report Share Posted March 31, 2011 And... Do any lights light up when the heater firsts shuts off (prematurely)? It may only light up for a brief time, so you have to be standing right at the heater to see the error light(s)when this happens. Quote Link to comment Share on other sites More sharing options...
Bob M Posted March 31, 2011 Author Report Share Posted March 31, 2011 You mentioned that the sensor is good. What was the resistance reading across the sensor? There are three temp sensors. 1) the temp sensor that goes into the fire box.(only has one wire) 2)Exhaust temp sensor. 3) the flow/temp/salinity sensor for the aqua pure. Which one should I test? The water temp sensor for the aquapure is accurate when compared to a thermometer. Quote Link to comment Share on other sites More sharing options...
Bob M Posted March 31, 2011 Author Report Share Posted March 31, 2011 And... Do any lights light up when the heater firsts shuts off (prematurely)? It may only light up for a brief time, so you have to be standing right at the heater to see the error light(s)when this happens. I havent done this but should be easy to do. I'll let you know if I see anything. Quote Link to comment Share on other sites More sharing options...
Pool Clown Posted April 1, 2011 Report Share Posted April 1, 2011 There is a temp sensor in the heater. That one. If you take an Ohm meter, and test resistance across the two wires (disconnected), it will give you a resistance. Compare to the chart below. Quote Link to comment Share on other sites More sharing options...
Bob M Posted April 2, 2011 Author Report Share Posted April 2, 2011 There is a temp sensor in the heater. That one. If you take an Ohm meter, and test resistance across the two wires (disconnected), it will give you a resistance. Compare to the chart below. I've watched the panel for error light when the heater shuts down but there are none that come on. I've also checked the ohm reading at different temps. To get the water temp past 97 I disconected the temp sensor and wired a 10k ohm resistor to allow the heater to remain on. Had it set to 100 and stayed on until 100 was reached, I then put it to 101 and heater came on and heated up to 101. This was just to get an ohm reading at higher temps. 62 = 14.59k ohms 97 = 6.57k ohms (this is where it shuts off) 100 = 6.22k ohms 101 = 5.6k ohms These seem in spec when compared to the chart. So I suspected the thermostat limit switch(s)were at fault or something on the board. On a hunch I unlocked the thermostat limit switches on the heater and rotated each one a couple of times. These had been locked in the same position for about 4 1/2 years. After reconnecting the temp switch I turned on the spa and set it to 101. Heater fired up and temp went to 101 without shutting off. So for now it is working. Many thanks to Pool Clown. This is the second time you have helped me with a problem. Sincerley appreciate your time and posts. Quote Link to comment Share on other sites More sharing options...
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