Electronics > Repair
Furnace circuit board repair - How stupid should I feel?
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rich t:
I think the lesson here is that if you disassemble appliances to the point of inspection, maybe half the time you find obvious discoloration near the failure, and the fix can be as simple as re-soldering, or often replacing a single component (connectors are notorious to fail as well, and often a clean and reseat and some dielectric grease to hold off further corrosion is all that is needed).  Our furnace motor failed a few years ago, and it was a dollar ntc thermistor that was supposed to limit inrush current that had blackened the pcb...  The dollar fix was much easier (and better for the environment) than replacing a $400 blower motor (and taking the old one to the dump)!
Excavatoree:

--- Quote from: rich t on July 19, 2024, 11:33:12 pm ---I think the lesson here is that if you disassemble appliances to the point of inspection, maybe half the time you find obvious discoloration near the failure, and the fix can be as simple as re-soldering, or often replacing a single component (connectors are notorious to fail as well, and often a clean and reseat and some dielectric grease to hold off further corrosion is all that is needed).  Our furnace motor failed a few years ago, and it was a dollar ntc thermistor that was supposed to limit inrush current that had blackened the pcb...  The dollar fix was much easier (and better for the environment) than replacing a $400 blower motor (and taking the old one to the dump)!

--- End quote ---

I know what I've done in this case doesn't show it, but that's my usual attitude.  Dishwasher, TV/computer monitor, the car,  lawnmower, whatever, I usually fix it myself.  I don't know why I was so afraid I'd really screw the furnace up.  I honestly thought I might screw it up so bad it'd cost more to fix than if I didn't make an attempt.  (how's that "rate chart" go?  Double the price "if you tried fixing it yourself..." )  As I said in another post, I think it was the heat frying my brain.   I honestly thought it might be some problem with the sealed system causing the blower not to come on or something.  I definitely spooked myself.
Runco990:

--- Quote from: Excavatoree on July 20, 2024, 01:23:05 am ---
I know what I've done in this case doesn't show it, but that's my usual attitude.  Dishwasher, TV/computer monitor, the car,  lawnmower, whatever, I usually fix it myself.  I don't know why I was so afraid I'd really screw the furnace up.  I honestly thought I might screw it up so bad it'd cost more to fix than if I didn't make an attempt.  (how's that "rate chart" go?  Double the price "if you tried fixing it yourself..." )  As I said in another post, I think it was the heat frying my brain.   I honestly thought it might be some problem with the sealed system causing the blower not to come on or something.  I definitely spooked myself.


--- End quote ---

Actually, do some reading!  HVAC is less complicated than you might think.  I know manufacturers are falling all over themselves to insert "complexity" into them to make them un-repairable, but the basic systems are very simple.  If nothing else, it's good to understand how these things actually work.   :-+
rsjsouza:
Excavatoree, I can relate. I fix everything at my house, including the furnace/HVAC system. Once I had a fan capacitor issue that prevented the external heat exchange unit from running. I replaced the caps (it was a dual capacitor), improved and cleaned the connections but the compressor wouldn't start on its own, unless I bypassed some protection switches on the heat exchanger using an alligator clip. I had a brainfart/paralysis moment and ended up calling a technician (on a Sunday no less!) as I was afraid I would somehow seize the compressor. He praised the work I had done on the capacitors but was in disbelief: his visit consisted in pressing a button of a gas trip breaker near the input of the compressor. I thanked him immensely for the information he taught me and chalked the US$179.00 emergency call fare as the cost of a training session. (He felt pity for me and ended up doing a major revision on the unit).

madires:
Yep, cracked solder joints are a common fault. And it's not related to mains voltage only. For example, failed 12V halogen lamp SMSPUs often have cracked solder joints at the secondary of the transformer.
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