I have a Whirlpool Duet Sport Electric Dryer. The Automatic dry cycle has been running several hours if not watched.

I downloaded the service manual and went through the diagnostic process. It reports an F-29 error: Moisture Sensor Shorted.

I pulled the plastic lint screen that holds the moisture sensor bars out. I tested the resistance across the bars with a multimeter (didn't really know what I was doing). No resistance from right to left across any single bar. Total resistance from bar 1 to bar 2. Total resistance from bar 1 to bar 2 when the circuit is closed with a wet paper towel. Service manual said to replace the bars. I think I just didn't have the multimeter sensitivity high enough.

Nonetheless, I purchased replacement moisture sensor bars and installed those with no problem. Retesting the bars. No resistance from right to left. Total resistance from bar 1 to bar 2. Partial resistance from bar 1 to bar 2 when the circuit is closed with a wet paper towel. Seems to be working fine.

I ran the diagnostic again, same F-29 error: Moisture Sensor Shorted. Followed instructions to disconnect the connectors on the moisture sensor bars and the control unit to test various wires and connectors between:
Part 1-Control Unit Connector wired into the harness
Part 2-Short 6" wire: plastic 3 pin on one side (2 into the wire harness, 1 to ground), 2 large resistors connecting each outer pin to the center ground pin; opposite side is 2 small plastic connectors that mount on the moisture sensor bars.
Part 3-Moisture sensor bars themselves.

Part 1...Total resistance between the two wires in the harness (testing at the plastic connector that I removed from the control unit): no short there. Ran the diagnostic without reconnecting that back to the control unit: no faults reported.

Connected the wire back to the control unit. Left Part 2 and 3 disconnected. Ran the diagnostic again: no faults reported.

Part 2...Total resistance between pin 1, pin 2, and pin 3: tested all combinations. No short there. No resistance between pin 1 and the corresponding small connector that would attach to the moisture sensor bar: working correctly. No resistance between pin 3 and the corresponding small connector that would attach to the moisture sensor bar: working correctly. The center ground pin only connects to the resistors.

Connected Part 2 to Part 1. Left Part 3 out of the equation. Ran the diagnostic again: no faults reported.

Part 3...check moisture sensor bars again. No resistance from right to left. Total resistance from bar 1 to bar 2. Partial resistance from bar 1 to bar 2 when the circuit is closed with a wet paper towel.

Connected Part 3 to Part 2 to Part 1: totally reassembled. Ran the diagnostic again: F-29 fault code, Moisture Sensor Shorted.

Out of ideas. Seems like each of the parts is working fine until they are all connected. Looked for Part 2 in the parts catalog: can't seem to find it. Thought maybe the issue has something to do with the resistors when the unit is actually fully running.

Any theories? Any easy way to narrow it down?

Thanks for your help.