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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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We are getting error code 91. Our american standard heat pump

Customer Question

We are getting error code 91. Our american standard heat pump and furnace are not working - this just happened. Any ideas? I have tried resetting the breaker...
Submitted: 1 year ago.
Category: HVAC
Customer: replied 1 year ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Video Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer: replied 1 year ago.
it's now been revealed that we also have error 53 and error 126. can you explain what these mean?
Expert:  Phil replied 1 year ago.
Hello again,Multiple and variable error codes very often point to a bad printed circuit card. Stress test the printedcircuit card.Use a hair drier toslowly and gently warm the card to 120F (warm to the touch butnot hot and not over 140F)... if you get any change in behavior thatmeans the card is bad... A micro crack hasopened in the printed circuit at a solder joint, or inside its CPU inthat case .... or a short circuit has developed as the cardexpanded when you heated it. Constantexpansion and contraction as these electronics heat and during theirduty cycles over the years is what wears these cards out. Itis also a good idea to replug all of the connections in the unit,that burnishes any oxidized terminal connections and will sometimessolve the problem, especially at the printed circuit card and in anysensor molex connectors. Do that with the power off to the unit ofcourse. Thesecards are also damaged by Electrical Spikes caused by power failuresand lightning. These high voltage spikes can literallyexplode the fine 'wire' connections inside the chip. There is also ashunt type device, often printed on to the card that allows a highvoltage spike to arc across to ground harmlessly, some of these canwear out after a few times and allow the high voltage spike into therest of the card and the CPU micro-circuits. The high end printedcircuit cards use a large capacitor like device, or several inparallel, to capture and release such surges, these do not wear out. ------------------- That is step #1, let me know what you discover, beyond that tell me a lot about your technical skills and experience, and if you have a multi meter or not, we can go from there. I will need a well focused, well lit, photo of the wiring diagram glued inside the blower access cover taken from straight on, and a photo of the printed circuit card showing the thermostat wire connections, and the letters on the card where there wires attach. Use the paper clip icon above for that. We can go from there.