TCM Magneto Hall Sensor

[Greg_D]

I decided to do a complete overhaul on my magnetos.  After putting them back on the engine everything tested great, with the exception that the tachometer is not working now.  I hope it's a broken wire, but decided to look at replacing the hall sensor if I can't find a wiring problem.  I almost fell over when I saw how much these things cost.  The best price I could find was from Airpower and it is $1291.48.  Does anyone know where a less expensive one can be found in case I need a new one?

[carusoam]

Doing a search around here you should find a few ideas.  

This topic comes up at least once each year...

Best regards,

-a-

[kortopates]

Good chance it is a broken wire at the connector. But to the un-initiated those sensors are exceedingly delicate and easy to break when removing a mag. If its not a broken wire, given the TCM replacement cost, it sure looks like great incentive to go with a replacement EI RPM meter (depending on your OEM size meter) or put the $ into a JPI EDM 9xx. The EI rpm unit doesn't even use a hall effect sensor, (its wired to your ignition key) and the EDM Hall sensor is ~$400 for replacement the next time it needs replacing.  

Salvage yards are another option.

Edited February 16, 2017 by kortopates

[N201MKTurbo]

That's crazy considering that the actual sensor costs about $1.00, the mill spec Honeywell ones are $3.50. My hangar ferries would probably repair it if it broke. 

[Greg_D]

It turned out to be a broken wire, right at the point where it enters the sensor.  Not much chance of repairing that.  I decided to go with the alternate unit from JPI for $255.  I considered the EI tachometer as a replacement, but the STC does not cover Ovations.  There's no way I'd consider a $10K EDM as an option at this point.

[kortopates]

It turned out to be a broken wire, right at the point where it enters the sensor.  Not much chance of repairing that.  I decided to go with the alternate unit from JPI for $255.  I considered the EI tachometer as a replacement, but the STC does not cover Ovations.  There's no way I'd consider a $10K EDM as an option at this point.

Great to hear JPI's sensor is compatible - was not aware.
Considering the cost that really sounds like your best option too.


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[thinwing]

I bet the mag shop had one for free

[kortopates]

I bet the mag shop had one for free

Why? These don't even go to the mag shop - they shouldn't and it's getting rough with them when R&R'ing the mags that breaks them.


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[thinwing]

The sensors on Mags get left on all the time 

[Greg_D]

I can confirm that the less expensive JPI sensor does work, if you remember to reset the tach circuit breaker   A side benefit is that the JPI unit comes with a Molex connector. Add the other side of the connector to the ship's wiring and you can easily disconnect the sensor when removing the mag in the future.  I still don't like the immediate 90 degree turn the wire has to make when exiting the sensor fitting though.

[Greg_D]

On 2/17/2017 at 9:53 PM, thinwing said:

The sensors on Mags get left on all the time 

At $1300 a pop, that's an expensive mistake.

[kortopates]

I can confirm that the less expensive JPI sensor does work, if you remember to reset the tach circuit breaker   A side benefit is that the JPI unit comes with a Molex connector. Add the other side of the connector to the ship's wiring and you can easily disconnect the sensor when removing the mag in the future.  I still don't like the immediate 90 degree turn the wire has to make when exiting the sensor fitting though.

Sounds like you are describing the sensor on the pressurized mags? That's what I assumed because those are the fragile ones compared to the standard unpressurized ones - which are very different? but you never mentioned, nor if slick or bendix? Your previous one was just butt spliced into the aircraft wiring?


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[Greg_D]

1 minute ago, kortopates said:

Sounds like you are describing the sensor on the pressurized mags? That's what I assumed because those are the fragile ones compared to the standard unpressurized ones - which are very different? but you never mentioned, nor if slick or bendix? Your previous one was just butt spliced into the aircraft wiring?


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These are non-pressurized mags on an Ovation (they are vented).  The previous sensor's wiring was soldered to the wiring bundle just aft of the baffling.  Not a good setup.  I'm not sure if that's how it came from the factory or not.

[kortopates]

These are non-pressurized mags on an Ovation (they are vented).  The previous sensor's wiring was soldered to the wiring bundle just aft of the baffling.  Not a good setup.  I'm not sure if that's how it came from the factory or not.

Most unusual, the factory usually uses Canon plugs.

The non-pressurized units entirely replace vent on mags. The pressurized mag has a different vent with larger orifice. Never understood why rpm sensors for the pressurized mags didn't also use a similar vent replacing unit but they instead chose to use a washer that fits under the original vent. Then the soft metal wraps around the mag. It's much like CHT gasket probe and similarly fragile.

 

You are much better off now!

 

 

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