Performed Furnace diagnostic on 2001 amana heater. Upon my diagnostic, Clients wife stated that he had been swapping out parts such as limit switches. I found that inducer motor and indoor blower were running continuously at the same time due to an open high limit. Error code 4 Was present on the circuitboard indicating that one of the limits are open. began checking voltage across all limits. Found that primary limit had no voltage although when Unplugging harness from the board And applying pressure Primary limit would close initiating the heating sequence. Therefore this indicates to me that this is a faulty circuitboard and needs to be replaced to prevent intermittent behavior. Will need to check availability of board considering this would be an aftermarket board due to the system being from 2001. Further investigation showed that indoor blower motor was also leaking oil and covered in a blanket of dirt this is due to the 1 inch filters inefficiently stopping dust particles from