exactly... as you stated.. an intermittent short in the P-lead, in our case
it was in the switch on the panel.
caused intermittent engine rpm power loss.. and when happening within a
short span of elapsed time..
a sense of "engine roughness" and 150rpm drop/fluctuation

Most older Pawnee's have two separate switches on the panel, not a keyed
rotary switch.

"Andy" wrote in message
...
On Apr 29, 4:56 pm, "BT" wrote:
To follow up on the P-Lead issue.. any short (break) in the old wire will
cause the problem as a bad P connector.

That's confusing to me perhaps because I think short and break are
opposite conditions. Maybe you meant a break in the P lead insulation?

A short to ground in the P lead will disable the mag, an open circuit
P lead will leave the mag hot but will not make any difference to how
the engine runs. Similarly an intermittent open in the P lead will
have no effect on engine performance. An intermittent short in the P
lead could cause the problems described by the OP.

In the case of my PA28-180 an incorrectly fabricated P lead connector
allowed the P lead circuit to intermittently short inside the mag
case.

Andy