Overhead light rheostat

[Ned Gravel]

Day before yesterday, after landing, the rheostat that runs the shoulder lights felt like it had rusted in place and was very hard to turn off.  Has anyone ever run into this before?  Is it curable with WD40?  Or Triflow?

If I need to buy a new pot, is it difficult to remove?

 

[N601RX]

I looked at mine when I had the console down and believe they were made by Ohmite.  I don't remember the wattage or resistance, but I use a lot of Ohmite products at work and they are usually stocked by allied electronics.

http://www.alliedelec.com/search/searchresults.aspx?N=0&Ntk=Primary&Ntt=reostat

 

[N201MKTurbo]

Just lube the shaft with your favorite lube. There is nothing in that rheostat that you will hert.

[Ned Gravel]

Quote: N201MKTurbo

Just lube the shaft with your favorite lube. There is nothing in that rheostat that you will hert.

[fantom]

WD-40 is thin snake oil, especially compared to TriFlow <")">

[DaV8or]

Triflow is flammable too. If you are worrid about sparks and fires, I would try contact cleaner first.

[fantom]

Quote: DaV8or

Triflow is flammable.......

[carusoam]

Fantom, 

Did I miss something....?

From the website source you gave, it appears that Tri-Flow is flammable as Dave suggested, at least during its delivery and early application....It appears that the solvent and propellant can be flammable.  The extreme condition that you reference may be an electrical spark.  The data sheet does indicate to use in a well ventilated area and then gives the following safety codes.

HMIS (NFPA RATING):

 

HMIS = Hazardous Materials Information System2, 4, 0     reference:   http://en.wikipedia.org/wiki/HMIS_Color_Bar      

Health = 2 of 4

Flammability = 4 of 4

Physical Hazard = 0 of 4

Tri-Flow contents include:

mineral oil - flammable?

PTFE = teflon - Listed as non-flammable, but with high dielectric strength  (is it OK to pump a high dielectric product into a rheostat??)  http://www.druflon.com/ptfeprop.html

hydrocarbon propellant - also flammable.

It seems that the Tri-Flow website is indicating a relative level of flammability. 

I like Tri-flow as a lubricant on mechanical devices.  While lubricating this one, I would leave the power switch off until it has an opportunity to dry.....

My milage varied....

-a-

[Ned Gravel]

So, next piece of news on this one.

First - no lubrication on any of it.  It appears, from the experience of someone who knows enough about these puppies, that any spray or lubrication without first taking it out is a bad idea. This was sent to me by one of our list members.

"Lubricant on the shaft would not hurt anything, but it will migrate to the wiper and cause a high resistance connection between the wiper and wire coil, and will get very hot and start smoking. These can be taken apart and cleaned.  If the shaft is sticking, just take some fine grit (400 or higher) sandpaper and clean it up, If the wiper is sticking and looks burnt, the wound wire core can be cleaned up with fine paper also.  If it is very badly burnt  it would be best to replace it.  My guess is that if it is sticking it is because of worn, rough or burnt places on the surface of the wiper or where it runs around the coil."  

Here is what it looks like.

As well, according to Clarence (the owner of my MSC) it is a Clarostst p/n #25-25.

So now I have to try and figure out a way to take it down from the overhead panel and inspect it to either clean it or replace it.

Thanks for all your very good information.

[DaV8or]

Quote: fantom

 ????? Maybe under extreme conditions, but I'd suggest you post some source data.

http://www.triflowlubricants.com/pdf/2009marchtflubesellsheet.pdf

YMMV

 

[fantom]

Better check that contact cleaner as well ;-) The warning on the can may be for the can. Acually the old salts at my airport use ACF 50 as a contact cleaner, but I've not checked it's flash point, nor do I pay much attention to legal warning notices on most products.

In any event, TriFlow is suggested often in my Mooney Service Manual, I've been using it for 20 years, and I'm still here.

Of course my milage could be better.

[DaV8or]

Quote: fantom

Better check that contact cleaner as well ;-)

[N201MKTurbo]

There is a big difference between what comes out of the can and what is left after the solvents evaporate.

If you just put a drop or two on the shaft, there won't be enough left behind to make much fire if any. The rheostat probably just needs to be cleaned, use CRC chlorinated brake parts cleaner, the red stuff not the green. The red is 1,1,1 tetrachloroethylene which is non-flammable, the green is alcohol which is very flammable, but it will all evaporate.

[bradtlew]

Hi Ned,

 

I see this is a pretty old thread, but have a similar question.  However, looks like people were more about the MSDS of lubricants?  I have  '65 M20C that I need to pull the Single overhead rheostat down and was wondering if you had any tips or tricks?  looks like it's behind the vent??

 

Thanks,

 

-Bradtlew

[Ned Gravel]

Bradtlew:

I pulled the headliner, took out the old insulation, pulled the vent box off and replaced the rheostat. I put everything back, including a speaker where the old one was missing, and the foam insulation. Now I have a rheostat that works, a speaker connected to my audio panel and a quieter interior.

Took about a day to get it all done.

But I am sorry, I do not have any pictures. It was done in 2011.

Ned Gravel

Lucky steward of C-FSWR, a '65 E model at Rockcliffe, Ontario, (CYRO)

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[Marauder]

I've been meaning to ask my northern friends this... Since you have a lot of letters in your C numbers, is it harder to recognize your call sign when everyone seems to be saying the alphabet?

[Piloto]

I just replaced the rheostat with a switch. It is more reliable and less prone to start a fire. After all the panel lights are not that bright and at night is like in IMC conditions. Navigating today at night is not like the old days were you were looking for the rotating beacon or the lighthouse using red lighted compasses. Even cars have GPS.

 

José 

[Ned Gravel]

I've been meaning to ask my northern friends this... Since you have a lot of letters in your C numbers, is it harder to recognize your call sign when everyone seems to be saying the alphabet?

 

Nope.

[Ned Gravel]

I use the new red shoulder LEDs to illuminate only the MP and the Tach parked at the far right of the panel (See the photo taken during a Fam flight with my neighbour's nephew) and the flap indicator down by the Johnson bar.  Clarence put Nulites in the panel when I bought C-FSWR, but those two instruments did not have enough room for one, so they were left out.  My shoulder lights were only for these two uses.

 

I can still use the dimmer pot on them because the underpanel light is also on the same circuit and it is an incandescent light.

 

 

[TheTurtle]

so I released all the blue smoke from my rheostat today..  Took the headliner down and it's burnt on the coils.  I found a bunch of different Ohmite 8ohm rheostats but does anybody know the wattage?  12.5w seems to low?  25w?

[M20F-1968]

I may have a replacement for you from my 67 F.  If you need a replacement I'll look through my parts.

John Breda

[TheTurtle]

11 hours ago, M20F-1968 said:

I may have a replacement for you from my 67 F.  If you need a replacement I'll look through my parts.

John Breda

looks like they are only $50 or so.  This annual has been painfulish (found a cracked exhaust downtube thats getting welded for im sure way more than its worth, a ripoff of an eddy current inspection and on and on so whats another $50 to never think about it again.

thanks for the offer though

for anybody looking for this later the one in it was 25watt.  1.77 amp max at 8ohms. heres the link to the part at Mouser.  http://www.mouser.com/ProductDetail/Ohmite/RHS8R0E/?qs=sGAEpiMZZMtC25l1F4XBUwuUYO8VJoEE091BXc58FNA%3d

Edited January 13, 2017 by TheTurtle

[Hector]

I converted the torpedo shoulder lights to LEDs and I like it a lot. The rheostat used to get so hot I could hardly touch it. With the LEDs it stays nice and cool and I can dim the LEDs as needed.


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