Stumped

I have a 1999 Mountaineer with a 302 and 97000 on it. Also fully loaded. I have a trouble code for a camshaft syncronizer sensor. Also, misfiring and what sounds like a valve tap. After replacing the sensor, the check engine light was out and it ran great until I turned the A/C on. The light went on, it misfired and the noise returned. After driving it for a few days without the air on, the light went out and it ran great. After putting the air on again the problem returned. I was told I need a syncronizer. Any help would be appreciated.

There may be a short between the two wiring systems. Use the wiring diagrams and check the wires, with a multimeter, for each system for the wires making connections (inappropriately) with each other.
Ford has a technical service bulletin covering the correct installation procedures for the camshaft position sensor synchronizer, which may be the cause of DTCs P0340, P1309, and P1336: Article No. 02-22-1, dated 11/11/2002.

Thanks, I’ll give that a shot.

A '99 with a 302, are you sure?

Absolutely, with AWD. Funny you should mention that. I am the second owner and when I bought the camshaft synchronizer sensor the one that was supposed to fit had three contacts, the one on the truck has two. Turned out the one that fit was from a 3 liter Ranger, two contacts. My parts guy [dealership] said he’d never seen that before. He wondered if the engine had been swapped out. The original owner worked for Ford and bought it direct.

Turns out it was a short in the alternator. Problem solved after replacing. Thanks for the input.