The International Cessna^® 170 Association

After reading all of the threads on panel light rheostats, it looks like most of you are replacing the old ones with 25 Watt versions and either 0-15 Ohm or 0-100 Ohm specs.

Those who have used the 15 Ohm rheostat, do they provide good dimming ability? Would the 100 Ohm work better since they are always ON and don't have a dead spot? I only have 2 Grimes lights, a couple panel bulbs, and the wet compass.

Thanks for all your help!

Mike, most of these types have no "off" position, but it is easy to modify one with a drop of epoxy at one end of the winding so the brush can ride up onto the cured epoxy.
My preference is the 100 ohm unit. I'll look it up and add it to this post.

Here ya go: Ohmite RHS100E, 25 watt, 100 ohm series "E".... order it from Allied, their PN 296-4094 http://www.alliedelec.com (800-433-5700) ...about $25... This is virtually identical ...may be identical...to what Cessna originally installed, and can handle your light load, as well as any future additions you're likely to make.

Thank you, sir. That's the one I was leaning towards.

You're not just going to throw that thing away, are you? You should make a new form out of fiberglass, then straighten out the ball of wire and re-wind it onto the new form! The problem with aviation these days is that nobody repairs stuff anymore. We're just parts replacers!

Sorry to burst George's bubble, but I ordered that rheostat when I redid the panel lights in my airplane replacing all of the sockets with new production versions as well as the wiring, bulbs, and rheostat when I installed a new shock panel I cut from my CAD file from Cessna drawings.

It did not work. Too much resistance and there was no dimming...just on/off. YMMV, but two EE friends of mine couldn't make the math work using the recommended rheostat and the stock panel light setup.

Get the 0-15ohm 25W rheostat from Aircraft Spruce. I did and my (7) 1816 bulbs work great with it.

http://www.aircraftspruce.com/catalog/e ... eostat.php

I'm using the same 100 ohm rheostat as George and I am very happy with the results.

I agree that most of the dimming happens in the first 25% of the turn, but I've had no problems getting it to dim from full brightness down to an almost imperceptible level. It's currently loaded with (7) 1816's in the panel.

Of course I'm not going to throw it away Dave! It will probably sit on my desk for a year, like the Concorde battery I replaced last year. Finally got around to recycling it last week!

Ryan and Christine, thank you too for your input. I needed some other stuff from Aircraft Spruce, so the 15 Ohm it is!

Has anyone relocated the rheostat to the panel or up on the ceiling in the plastic cover for the grimes lights. I have a 1954 B and we are looking at panel changed now. Also there is a small black thing mounted on a bracket right behind the center of the panel that says "thermostat" I didn't see it in the IPC. What is that?

I found it in the IPC. It says circuit breaker. What is it for?

Circuit breaker is an Klixon automatic reset type used for your turn and bank and for some reason I'm thinking something else but can not think of it.

I would NOT put the rheostat in any enclosed space. It gets warm and has the capability to get very hot under normal use. This is why it was mounted in open air under the panel

Thanks. I guess I'll keep it where it is.

Ryan, I'm wondering if you don't have another issue with your installation.
The advantage of the 100 ohm unit is that addt'l lamps can be added if ever necessary without having to re-invent the wheel, and the windings are more robust/durable than lighter-duty units.

[quote="gahorn"]Mike, most of these types have no "off" position, but it is easy to modify one with a drop of epoxy at one end of the winding so the brush can ride up onto the cured epoxy.
My preference is the 100 ohm unit. I'll look it up and add it to this post.


I just installed the same 0-15 ohm rheostat model that Ryan used and it seems to work well. All of its dimming on my 6 bulb panel took place in about 1/2 of its rotation. In order to give it an 'off' position like George mentions, I simply cut out a half circle of Teflon tape and pressed it onto the windings. This too works great. (I found this tape at a wood working store for reducing friction on a table saw, but Teflon is also a very good electrical insulator.)
Dave P.