The International Cessna^® 170 Association

Arash,
It is in the C180 and is some sort of synthetic but I don't know what kind. It was installed in 1991 when the interior was done. I told the interior shop (that is not there anymore) to put in something water proof in case the windshield leaked but it never has. They did a nice job and the headliner has stood up very well to some rough treatment. The 180 has hauled lots of stuff that has poked at the headliner like lumber, building supplies, and caribou and moose antlers. So far it just takes it without puncturing. I wish I knew what they used, the logbook only says the complete interior was replaced and all materials meet burn specs.

With the airplane down for a while due to the damage from the tailwheel spring breaking, I've got the airplane torn apart to start the wiring upgrades. Dad put a PAI-700 vertical card compass in the airplane but never wired it into the lights. While tracing some extra wires running to the rheostat that I was not expecting, I had my IA out looking at wires and cross-referencing the IPC, and I see that there is supposed to be a 10W 60ohm resistor wired between the compass light and the panel rheostat. I had planned to connect the wires for the compass light in series with the other lights, but in the IPC it shows them being wired separately.

If I wire the compass in series with the rest of the lights, can I forego the resistor that's shown in the IPC? I am trying to locate paperwork on the compass, but so far, no joy. Also, Richard stated that I should twist the wires for the compass light so as to minimize the magnetic field causing error in the compass...since I am putting some sort of disconnect, do I need to twist the wires all the way through the other side of the connector to where the solder into the sockets for the light sockets?

Any help is greatly appreciated, and please forgive the neophyte questions.

The 10 watt 60 Ohm resister simply sets the compass light at a single brightness, less than full, but not variable as the rest on the rheostat.

The resister could be removed or the resister adjusted in Ohms to change the brightness as needed depending on the bulb(s) in line with it.

Is your compass light to bright? If so you may want to add a resister. If not, don't change it.

Bruce Fenstermacher wrote:The 10 watt 60 Ohm resister simply sets the compass light at a single brightness, less than full, but not variable as the rest on the rheostat.

The resister could be removed or the resister adjusted in Ohms to change the brightness as needed depending on the bulb(s) in line with it.

Is your compass light to bright? If so you may want to add a resister. If not, don't change it.

I couldn't tell you. The wire sat in a bundle for a decade on top of it until I pulled them through for this project. It looks like the compass light was originally wired separate to the rest of the panel lights...still on the dimmer rheostat, but not in series with the rest of the lights.

Aryana wrote:Mine is located at the top of the windshield, no resistor, no twisted power wires either. The wires are in a plastic sleeve that routes them right into the headliner. I think they are connected up to the overhead Grimes lights that are red. Has been rock solid especially since I bought the right mount that dampens all the vibrations.

I found this but not sure it is much help for you Ryan.

Good enough for me! Thanks Arash!

The original wire is NOT on the rheostat, at least the power to the compass light does not pass through the windings of the rheostat. According to the schematic the compass light wire comes branches off at the input terminal to the rheostat. Big difference. The rheostat has no effect on the compass wire circuit.