Weird Basement A/C problem

[JB Texas]

'02 UA 40J here. Similar problem with my A/C. With heat pumps working normally, when T-stat is satisfied the heat pumps shut down but fan keeps running. If I turn on/off bedroom light, hall lights, or living room lights the fan will shut down. Problem doesn't occur every cycle. I had suspected a bad 12V ground somewhere but the interference theory makes more sense. I think I will try the inline filter that John C. mentioned.

[Moder2]

just to see if it worked, I put an RF choke around the wires going to/from the tstat. So far I haven't had the problem reoccur. I just used a 2 part iron core choke I got at radio shack and wrapped as much of the wire around it as I could.

So far so good. I would be curious to see the filter that the tech installed in John C's coach...

John

[John_Canfield]

John - I didn't get a good look at the module but I imagine it had a toroid or choke like you made and maybe some bypass capacitors.

Hopefully you have the problem licked and have greatly contributed to the forum data bank