I have a 1998 vintage (Home Depot) Jacuzzi Spa Echo model Z-145. Control panel has a temp control knob, status heat indicator (led) & a function control button. No troubleshooting display other than the led. H136 System wiring diagram. Has an ozone generator, original. 220 volt setup.

Problem: the heat indicator light blinks, the system does not cycle on its own and heat up. The led blinks what seems to be one second on & one second off.
I can start the sytem with the control button, the heat light comes on and the system works normally, heats up etc. useable.
When I look at it say the next day the led could be blinking and if its serveral days until I look at it the water is cold. Again if I press the button it starts to heat up and work normally. It does reach the normal temperature of 102F.
If I turn the circuit breaker off than on the tub starts to cycle normally. I did install a new pressure switch and calibrated it ,no change. I have cleaned the filter. Not sure what to look at next?

Sounds like a High Limit error, The LED is a error indicator:

I believe you are correct it is a " High Limit error". I am not sure what is causing the HL problem. I have not checked the HL sensor or the temp sensor yet..
Today I ran the spa, the floating thermometer showed the water temp to be 104, everything seemed to be working fine both Hi & Lo speeds. I shut the spa off using the control button and watched. In a very short time LED was blinking the same HL error. The floating thermometer still showing approx 104. Water temp felt like 104 not much higher.

In a short time I notced the following: still no pump running, spa has been off for a minute or two, led blinking HL I notice a slight movement or flow of water from a jet. Jet closet to the control panel located in the lounger. It didn't look normal. When I put my hand in the water close to the flow the water was extremly hot that was coming out of the jet!
Could there be enough residual heat in the heater to heat the water up that much, cause a HL error and cause it to flow? Could heaters be staying on even if the pump is off.
Not sure what to try next.

Sounds like it to me. Do a voltage check on the heater element leads, and if possible do an AMP check both with the pump running and off.

I bought my hot tub the same year, same model, same retailer, same problem. Tub never gets hot so it is hard for me to believe high limit protection sensor is triggering. My guess is that other people have had the same problem with this model. What is the final solution. Chucky5 no longer is a member.