Anybody know what might be causing a knocking sound from a new air handler when the outside condensor shuts off? Doesn't seem to matter whether the blower is shutting off, or going from high to low speed, the common denominator seems to be when the condensor shuts off. The sound last about 3 seconds and seems as if it might be coming from where the lineset connects to the handler. Or possibly even the linset itself? Carrier Comfort series heat pump.
Any thoughts or test-tips would be appreciated, am just trying to narrow it down further before calling the dealer.