Raypak heating problems

[double83]

Hi there,
I'm having a strange problem with a new Raypak r266a - electronic ignition pool heater. Here is the situation: when the heater is off, it accurately reads the pool temperature at 71 degrees. Then when the heater is turned on and set to 85, the pool temperature reading on heater display starts climbing quickly, until it reaches the setpoint of 85 and shuts off. The whole process only takes about 1 or 2 minutes. The pool water temperature has not changed obviously, but the heater thinks it has hit setpoint temperature that quickly. The pool temperature reading on the heater display then starts falling and the heater turns back on. The heater is cycling on and off constantly and not heating the pool properly.
Does anybody have any ideas what could be causing this issue? The heater is only one year old! I haven't been able to find anything related to this online.
Thanks!

 

[ps0303]

Could be the temp sensor, maybe. You cold warm up a glass of water, test with a household thermometer and then take the heaters temp sensor out and stick on the water and see what it reads. If it reads correctly then you know that part is good.

 

[Pool Clown]

Is the heater making any noise when it runs? Like groaning or hissing? Maybe a little popping. May not be very loud. Check to make sure that the heater is not plumbed backwards. Inlet from the filter, outlet goes back to pool.