I recently converted a failed X-13 motor on a Goodman GPG1536 (08′ model) with the 4-speed selection tap (Low Cool, High Cool, Low Heat & High Heat) to a regular 3-speed PSC motor application utilizing two SP/NO "peanut" style relays. I used the original wires feeding both the dedicated high voltage & low voltage molex plugs. Being a 208/230vac application I had one dedicated leg (L2) to the motor and broke my other leg (L1) through the switching sides of my relays. I had one relay for Cool (Highest Speed) & one relay for Heat/Continuous Fan (lower speed).
I spliced low voltage common to one side of both coils on the relays and used Low Cool as one hot signal & both low heat & high heat as another hot signal to engage the coil for my heat/fan relay (continous fan engaged High Heat). Tested operations and motor ran to spec and within amperage range on all speeds. The issue that arose was blower would never stop running due to constant low volt signal from PCB. Unplug connection at board and plug back in and problem would stop until blower came on again. I could unplug my 24V hot at the relays and PCB would engage both blower on delays and off delays measured at board without a hitch. Replaced relays with sequencers and bypassed blower connection at board and straight wired to tstat G, Y1 & W1 to simulate blower on & off delays. My theory is that somehow backfeeding was occuring through relay due to motor speed legs producing CEMF when running. Has anyone else encountered this issue before and can give me a defintive answer as to why this was occuring?
BACKSTORY… I have been milking this unit along and was not the original installer. Unit was struck by lightning/surged in the past. The system was never wired up for 2 stage operation or designated correctly at board to engage 2-stage heating. The last repair was finding a shorted 2nd stage coil in the compressor and customer just wanted to bypass 2nd stage and have only low stage operation in cooling (I know, I know :beat:) This is the customer that is a "electrical engineer" and has seen several websites and youtube videos on converting X-13/ECM motors to PSC applications and wouldnt go for OEM replacement. I must say though; I have converted several motors before and this is the first to show these symptoms.