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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8679
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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When starting my Hayward 400000 btu heater after it started

Customer Question

when starting my Hayward 400000 btu heater after it started the service lite came on and the number on the temp dial went from 85 to 56. None of the buttons would do anything and the only way to turn the unit off was to turn off the breaker to the pump. What is wrong and how do I fix it?
Submitted: 2 years ago.
Category: HVAC
Expert:  Phil replied 2 years ago.
Welcome! We keep going until you have all of the information you need.[b/]. Extensive training & coaching also available.
With that set of symptoms it is at least 90% likely that the electronics control module is bad.
You can stress test the printed circuit card. (electronics control module) to confirm this diagnosis in about 50% of the cases.
Use a hair drier to very *slowly and gently warm the module to 120F (warm to the touch but not hot and not over 140F)... if you get any change in behavior that means the module is bad... you have to warm it slowly enough over a 30 minute time span to insure the printed circuit card inside gets up to 120F or so.
A micro crack has opened in the printed circuit at a solder joint, or inside its CPU in that case .... or a short circuit has developed as the card expanded when you heated it.
Constant expansion and contraction as these electronics heat and during their duty cycles over the years is what wears these cards out.
It is also a good idea to replug all of the connections in the unit, that burnishes any oxidized terminal connections and will sometimes solve the problem, especially at the printed circuit card and in any sensor molex connectors. Do that with the power off to the unit of course.
These cards are also damaged by Electrical Spikes caused by power failures and lightning. These high voltage spikes can literally explode the fine 'wire' connections inside the chip. There is also a shunt type device, often printed on to the card that allows a high voltage spike to arc across to ground harmlessly, some of these can wear out after a few times and allow the high voltage spike into the rest of the card and the CPU micro-circuits. The high end printed circuit cards use a large capacitor like device, or several in parallel, to capture and release such surges, these do not wear out.
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We are on the honor system here. Please remember to rate my service before you leave today. If you need anything else, just let me know. You can continue asking follow-up questions at no additional charge.
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Customer: replied 2 years ago.
I haven't tried any of the repairs you have sugested yet , but they are logical and I am sure they will work. Thank you
Expert:  Phil replied 2 years ago.
Hello again, let me know when you have done that cleaning and adjustment, that has about a 70% chance of solving the problem, not 100% however... we go from there accordingly until we finally do get the problem resolved.
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We are on the honor system here. Please remember to rate my service before you leave today. If you need anything else, just let me know. You can continue asking follow-up questions at no additional charge.
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