RPM indicator

[Juan M. Padrón]

Hello everybody:

The RPM indicator portion for the front engine in my 337 B was not working.I took it to the shop and what was wrong was the sensor in the corresponding magneto.This sensor was rusted and the problem is that they are not in use anymore so they can not be found in the market,that is what the people at the shop say.In order to solve this problem ,and for not having any more trouble in the future,I would have to get a new indicator and then I would have to get at least two new magnetos,since the one I have cannot be converted to the RPM sensor type used nowadays.I think this is becoming too much and too expensive.
Have anyone had this problem before? Does anyone have an idea how to solve this problem?Thanks for any reply.

[Bob Cook]

Juan

1) these mags can be overhauled.
2) the sensor is just a second set of contacts.
3) There are lots of used ones on the market and parts should be available from Bendix.
4) There are numerous RPM guages that use the "P" lead for frequency or RPM of engine. -- JPI for one. AE for another.

5) Suggest you have your mags overhauled or order the parts. You need to supply the part number of the mags you have including the engine information, otherwise, we are guessing at what you have.

regards

Bob

[Ernie Martin]

Juan:

I agree with Bob. On my old '69 337D, I was initially told that they couldn't be overhauled. Further digging suggested otherwise, but it had to be done at the factory instead of my local magneto shop. If that's too expensive, do as Bob suggests and find a used one -- suggested sources are in the "Purchasing Parts" page of my backup Skymaster website at www.SkymasterUS.com

BTW, you should need only ONE magneto, the one with the RPM contacts, not two.

Ernie

[Juan M. Padrón]

Thank you Bob,Thank you Ernie:

Ok,the magnetos I have are:Part# S6LN-25 Mod.10-79020-16.
Is there any particular place that I could order the parts for overhauling these magnetos?Regards.

Juan M. Padrón

[Bob Cook]

These mags should be sent out and overhauled by a reputable shop. They should be overhauled every 500 hrs regardless..

I am sure that most overhaul shops would charge about the same amount for testing and replacing worn parts.

Not sure where you are located to recommend someone.

bob

[Juan M. Padrón]

Thank you Bob.Here is the whole story:Since the rear engine rpm indicator was not working,well it actually worked but erratically,I sent the RPM indicator for overhaul.The people at the instruments shop told me that the indicator was ok and that the problem was in the magnetos and that this indicator work with the signal sent by a coil in the magnetos,then we talked to the mechanics and effectively the coil in the magneto was damaged.The instruments shop recomended to use the old indicator as a core and adapt it for the system in use nowadays which work with a set of contacts in the magnetos and there would not be any problem
adapting the magnetos,so I agreed,and supposly in the future I would not have any more trouble since the contacts were easy to find and the coils are no longer in use.
So far ,so good.The problem began when the shop that repair the magnetos told us that these magnetos could not be adapted to work with the contacts and that I should get two new magnetos (part:S6LN-25 Mod. 10-79020-11).So ,
what do you think?.
I am located in Maracay,Venezuela.I get my spare parts and accesories from people in south Florida.Regards.

Juan M. Padrón

[Francisco]

Juan, Last week I had the sending unit replaced on the front engine, got a replacement from Comodore aerospace cost $ 250
Call Don he may have more.

PS you can avoid having to send off your gauge in the future just have your mechanic check the gauge by conecting the rear sending unit to the front engine gauge, and if it works then you know it is not the gauge. That is how we found the problem in my 336

Buena suerte (good Luck)

Saludos,

Francisco

[Paul Sharp]

Commodore Aerospace (Don Neiser): 405-722-4079.