Interior Light Question

How to keep the Cessna 170 flying and airworthy.

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CloverCrusher
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Interior Light Question

Post by CloverCrusher »

Went for my first night flight in my 170A last night, and now I have a question about the instrument panel lighting. On my panel, I have the piano key for instrument lights, which runs through a dimmer rheostat on the panel. Both of these work just fine - but only the oil temp, oil pressure, ammeter, and radio face light up... basically, just the bottom row of gauges.

The flight instruments and tachometer in the top section of the panel (is this the "floating panel" ?) had no back-lighting at all. Fortunately I have a grimes light on the pilot's door post that lit up the whole panel just fine, and I was able to accomplish my 3 full stop night landings with (relative) ease. Now for the questions...

1. Are the top row gauges "supposed" to have lights, or is that the purpose of my grimes light?
2. What is everyone using as the replacement for when they inevitably burn out? LED or otherwise...
3. What is the best source for a replacement dome light bulb assembly (preferably LED)? No matter how many times I flip the switch the darn thing still doesn't turn on! :D

Thanks!
Jake
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brianm
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Re: Interior Light Question

Post by brianm »

My '48 doesn't have any lights (ring, post, or whatever) in the upper panel. The engine instruments are lighted and the same rheostat controls those lights and the radio lights. On/off is via the nav light switch. I also have red torpedo lights on the door posts and a white center torpedo light. Those have their own switches and are just on/off. I'm not sure how helpful that info is, my electrical system was butchered at some point in distant past. This winter I plan to put ring lights in the upper panel and do a firewall-aft rewire to clean things up.

I've been using these LEDs in my torpedo lights: https://www.amazon.com/gp/product/B06W9FYNYG

They don't work with the original covers with the 90 degree bend in them. I had a friend 3D print new straight covers out of ABS. In this thread, gahorn shows how to make covers out of PVC parts: http://cessna170.org/forums/viewtopic.p ... s&start=15
Brian M
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n3833v
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Re: Interior Light Question

Post by n3833v »

My 48 has lights on all instruments and they are the squeeze and insert into holders. It sounds like you lost the ground or the bulbs are blown. They are difficult to access but doable from up behind the panel.

John
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bsdunek
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Re: Interior Light Question

Post by bsdunek »

As John says, there are lights behind the panel cover, although, from the parts book, the simple, non-optional panel may not include lamps. Three across the top and two on the bottom. As for the lower panel with oil press, temp., etc. there are two. They are retained by "pinch-in" socket assemblies. There are two problems with these. First is the aluminum plate that the instruments are mounted in grounded? If not, none of the lights will work, so, is you have some, it must be. Second is that that plate corrodes and the socket mounts don't ground to the plate. I just went over all of mine a couple of weeks ago, as only two of the five worked. A little work with some sandpaper and a small knife will fix that problem. Of course, you want to check all the bulbs. With the 'advances' in technology, it's hard to find the bulbs now. The 170 parts manual I have just lists Cessna's part number, not industry standard. I think this might be the right size: http://www.bulbtown.com/756_Miniature_B ... p/b756.htm Of course, they need to be red. Radio shops used to sell little bottles of red lamp dye - can't find it any more. I have a handful of lamps in my spare parts supply that I sprayed with red lacquer. Seems to work OK.
My 170 has an overhead light that shines on the whole instrument panel. When Dad put that in, he disconnected all the in-panel lamps, as that was the way they did it. When I got the 170, I reconnected them and run both. I like that better.
Sorry I got long winded - just hope it helps.
Bruce
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brian.olson
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Re: Interior Light Question

Post by brian.olson »

Jake - I noticed the same thing on my '50 170A. Just completed my first night pattern work Wednesday evening, and my lower panel illuminates fine with the rheostat, but the main flight instruments in the floating panel are only lit by the red overhead light wash (and very dimly at that). I'm thinking of having a torpedo light installed. Let me know what you discover in your sleuthing - whether the lights are there and non-functional (and, perhaps, if any of the solves other posters have suggested work). Candidly, I'm new enough to airplane ownership that I will likely need to defer this to an A&P for a first swipe.
Brian
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n2582d
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Re: Interior Light Question

Post by n2582d »

I think the most comprehensive article on the instrument panel lights is found on the Cessna 120-140 website. I have a link to it toward the end of page one in this thread.
Gary
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Re: Interior Light Question

Post by 170C »

Note the earlier post referencing George Horn's method of converting to led lamps. I have done so for map lights, navigation lights as well as the overhead lamps that illuminate the instrument panel. They are nice and bright, but the ones I used cannot be dimmed. There may be led lamps that can be dimmed with the dimmer, but some cannot.
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Re: Interior Light Question

Post by brian.olson »

In observance of the Keeping It Simple method, I think I'll first replace the overhead lamp with a LED and see what (anticipating: positive) impact that has on my particular situation before launching into a panel dissection. Great suggestion -
Brian
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Re: Interior Light Question

Post by GAHorn »

Jake (and others) I modified my instrument panel a number of years ago and mentioned it in a different thread but never posted the details.

I used "grain of rice" incandescent lamps which are small (like a grain of rice) and using modular phone-cord and connectors created indirect instrument lighting behind my false instrument panel. (obtained the GOR lamps from an online source, very cheap) I placed 3 GOR lights at each large/gryo instrument and 2 at each smaller instrument. It looks like (and beats the cost of...less than $30 total) Nulites. Twisting the electrical leads and hot-gluing the twisted lead to the backside of my false panel I used a telephone, modular quick-disconnect (the exact same stuff your ELT installation uses to introduce a remote switch to the cockpit) to tie it to the rheostat which powers the overhead direct-lighting system Cessna had originally. (Allows the false panel to re easily/quickly removed for instrument mx.) It works fantastic now for about 5 years.

I'll take a pic of the result and post it. It is signed off by my A&P/IA as a minor alteration, as it supplants, not replaces, original lighting.

Here's a pic taken in my lighted hangar with instrument lighting OFF.
InstLts.jpg
Here's a pic in same conditions with instrument lighting ON (but with my other hand blocking out the red overhead Grimes so you can discern the GOR lights only.)
instLts2.jpg
Here's the effect with the Red Grimes in conjuction.
InstLtsRed.jpg
With the rheostate operation the degree of brightness is much better than depicted in these poor photos.
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brian.olson
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Re: Interior Light Question

Post by brian.olson »

Impressive, George. Thank you very much for sharing.
Brian
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lowNslow
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Re: Interior Light Question

Post by lowNslow »

George, very nice set up - looking forward to the picture of the wiring. These "grain of rice" lights are now available in LED, I'm wondering if they would work as well as the incandescent lights you used?
Karl
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Re: Interior Light Question

Post by 170C »

George, when you replaced the Grimes torpedo fixtures/lamps in your overhead and connected them to your instrument panel lights, are you able to dim the led's in the overhead?
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Re: Interior Light Question

Post by Bruce Fenstermacher »

I'll answer for George. If he has LEDs connected to a rheostat, he will likely see some dimming but in reality LEDs are not dimmable. What George might be seeing is the LED working at it's minimal voltage or under driven at the dimmest and at an over voltage state or over driven when they are the brightest. If he sees a dimming effect it likely will be a very short range on the total rheostat rotation.

What you say, LEDs in my house and my flash light are dimmable. And you would be right, our eye sees more or less light. But the effect is not because the LED is dimming, it's because the LED is being turned on and off with an electronic pulse so fast your eye can't see it going off and coming back on. We see less light. George could have such a circuit but it's not a simple rheostat.
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GAHorn
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Re: Interior Light Question

Post by GAHorn »

:wink:
170C wrote:George, when you replaced the Grimes torpedo fixtures/lamps in your overhead and connected them to your instrument panel lights, are you able to dim the led's in the overhead?
Yes.
Bruce Fenstermacher wrote:I'll answer for George. If he has LEDs connected to a rheostat, he will likely see some dimming but in reality LEDs are not dimmable. What George might be seeing is the LED working at it's minimal voltage or under driven at the dimmest and at an over voltage state or over driven when they are the brightest. If he sees a dimming effect it likely will be a very short range on the total rheostat rotation.

What you say, LEDs in my house and my flash light are dimmable. And you would be right, our eye sees more or less light. But the effect is not because the LED is dimming, it's because the LED is being turned on and off with an electronic pulse so fast your eye can't see it going off and coming back on. We see less light. George could have such a circuit but it's not a simple rheostat.
The LEDs I ordered online are dimmable. They work full range thru my rheostat exactly the same as incandescent lamps. In fact, the indirect incandescent GOR lights I discuss above and the overhead grimes "torpedos" in which I've replaced the original incandescent with LEDs are actually ALL controlled by the single, 25 watt, 10) ohm Ohmite Series E I've mentioned in other threads.

SOME LEDs ARE DIMMABLE with ordinary rheostats and some are not. I'll edit this post shortly with a link to the original post I made when replacing my torpedo lamps w/LEDs for reference purposes.

Here's the post in which I described how I replaced all my nav lights as well as my interior Grimes "torpedo" lights with LEDs. (See page 2 for the overhead torpedo modification.) http://cessna170.org/forums/viewtopic.p ... LED+lights
All the interior LEDs I used are dimmable with ordinary rheostat.

Addendum: In the link posted just-above.... on page 2.... and for those who need a REALLY WARM REMEMBRANCE of our Dear-departed BLUELDR...., Be certain to re-read his comment immediately following my description and pics of my overhead torpedo mod,...those comments he made on Wed May 13, 2009 12:12 pm regarding my modifications. (I really do miss him.)
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Re: Interior Light Question

Post by Bruce Fenstermacher »

So the LED that George bought is not just an LED it us an LED with a dimming circuit as I described. Amazing how small these circuits gave become. 20 years ago the 555 timing chip alone was as big as your finger nail.
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