The original 1943 Airpath B-16 compass in my L-4 had a mind of its own. It couldn't be properly swung. Flying along I'd often notice that not only was the displayed compass heading wrong, it was wildly wrong. Checking and eventually overhauling the compass didn't help. Neither did degaussing. It didn't matter whether the radio and ignition were on or off.
I don't navigate with reference to the compass, so I just put up with the problem. Then, inspiration struck.
My original WWII US Army tach with Hobbs meter was located immediately to the left of the compass, with the airspeed indicator on the far left, where I could see it with the front seat occupied. Was the tach interfering with the compass? Turns out it was. Switching the positions of the airspeed indicator and tach fixed the errant compass indications. The moment the tach was dropped out of the panel the compass swung and neatly aligned with the surveyed axis of the hangar. Properly swinging the compass on our compass rose was a snap.
FWIW. Old installation:
I don't navigate with reference to the compass, so I just put up with the problem. Then, inspiration struck.
My original WWII US Army tach with Hobbs meter was located immediately to the left of the compass, with the airspeed indicator on the far left, where I could see it with the front seat occupied. Was the tach interfering with the compass? Turns out it was. Switching the positions of the airspeed indicator and tach fixed the errant compass indications. The moment the tach was dropped out of the panel the compass swung and neatly aligned with the surveyed axis of the hangar. Properly swinging the compass on our compass rose was a snap.
FWIW. Old installation:
