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G3x Touch No RPM indication

Sportquattro

Well Known Member
Hi everybody,

OK, over the weekend we did the first engine start on my RV9A (O-320) and fortunately it started right up and ran very nicely which was a massive relief.

The only problem we had was the RPM not registering on the G3X Touch display.

So far we have checked the following:-

The Sensor is the T1A9-1 for the Slick Magneto
The Sensor is in the correct port on the magneto
The wire connections appear to be correct
It is configured under RPM1 in the settings

My next plan is to move the sensor from the Left to the Right magneto as other than it being a duff sensor I can't think of anything else to try before replacing the sensor.

If any knowledgeable soul has any top tips as to anything I may have missed or ways to test the installation then I would welcome all suggestions as changing the sensor isn't going to be easy to do due to limited access behind the panel (Slider canopy)

Thanks in advance
 
I imagine that there is a configuration setting to tell the G3x what kind of sensor is being used. Need to go deeper into the config settings. Can't imagine the system can decide by itself whether it is looking for a tach signal vs a magnetic sensor.

Larry
 
I imagine that there is a configuration setting to tell the G3x what kind of sensor is being used. Need to go deeper into the config settings. Can't imagine the system can decide by itself whether it is looking for a tach signal vs a magnetic sensor.

Larry

Hi Larry, there is indeed, problem is it is configured so I'm a little stumped as to what else to do as I have done all the obvious bar changing the sensor or swap it over to the right magneto
 
Tach sensor

Check T1A9-1, orange/white wire to GEA 24 terminal 9.
White to GEA 24 terminal 8.
Blue/white to GEA 24 terminal 7.
Configure G3X rpm input 1 to T1A9 and set to 2 pulses.
Check with Multimeter set to Vdc, +12 V on orange/white wire vs GND.
To check signal T1A9-11 sensor when mounted on magneto.
Connect orange/white to +12V, blue/white to GND.
White wire to Multimeter set to Vdc, other multimeter wire to GND.
Rotate prop slowly with magneto in the OFF position.
Voltage should indicate square wave 0 or 11 V.

Good luck.
 
I had the same problem two weeks ago.

I made a simple mistake of not realizing the tach wire was shielded, and I didn’t remove the braided shielding, thus the rpm pulse was being sent to ground. If it wasn’t pointed out to me I’d likely still be looking.
 
I made a simple mistake of not realizing the tach wire was shielded, and I didn’t remove the braided shielding, thus the rpm pulse was being sent to ground. If it wasn’t pointed out to me I’d likely still be looking.

Hi CJ, thanks for your post in reply to my problem, am I correct in my reading of your post that the shielding on cable from the sensor should not be connected to anything i.e. grounded? I'm going to try an wriggle my fat self under the panel and check the connections and hoping it something simple like a shield that's grounded that shouldn't be. Unfortunately my wiring guru is out of the country at the moment so it's down to me to try and figure what's what in a tiny tiny space
 
I know I'm going to say this incorrectly so feel free, all you engineers, to correct me. When I updated my panel I had the same issue. I have Lightspeed ignition and was informed by Klaus that the tach signal Garmin looks for is "non-standard" and needed to place resistors in line to bring the signal voltage from Lightspeed's voltage to Garmin's. It's been 5 years but I think I placed a few resistors in a parallel configuration until I had success. It took several combinations. I can go and see exactly what Ohms made the magic happen. I'm not sure if this hold true for any other ignition system. I apologize to all engineers for butchering my explanation :)

David
 
I know I'm going to say this incorrectly so feel free, all you engineers, to correct me. When I updated my panel I had the same issue. I have Lightspeed ignition and was informed by Klaus that the tach signal Garmin looks for is "non-standard" and needed to place resistors in line to bring the signal voltage from Lightspeed's voltage to Garmin's. It's been 5 years but I think I placed a few resistors in a parallel configuration until I had success. It took several combinations. I can go and see exactly what Ohms made the magic happen. I'm not sure if this hold true for any other ignition system. I apologize to all engineers for butchering my explanation :)

David

Hi David, thanks for the response, according the the Garmin Install (I'm using Slick magnetos) they don't mention a resistor, I have a feeling that some systems do if your using a P-Mag electronic ignition. From what I can tell my sensor is wired as per the Garmin Instruction with the Shield grounded hence my post #6 to CJ in EP regarding the reference to the shield in his post #5 which has me confused (it doesn't take much). If any of the excellent knowledgeable folk on here can confirm if I need a resistor to make it work with a Slick Magneto and G3X touch I'd welcome comments.
 
Tach sensor

https://umainstruments.com/wp-content/uploads/2021/04/SpecNT1A9-xRevA-2.pdf

The shield is internally connected to white/blue wire within T1A9-1 sensor.
The shield may be connected to GND on the GEA 24. With the shield not connected to GEA24, it should work just fine.
A resistor is NOT called for when using the T1A9-1 sensor.
Check with Multimeter set to Vdc, +12 V on orange/white wire vs GND.
You need to see +12V on the orange/white wire vs GND.

Good Luck
 
Hi David, thanks for the response, according the the Garmin Install (I'm using Slick magnetos) they don't mention a resistor, I have a feeling that some systems do if your using a P-Mag electronic ignition. From what I can tell my sensor is wired as per the Garmin Instruction with the Shield grounded hence my post #6 to CJ in EP regarding the reference to the shield in his post #5 which has me confused (it doesn't take much). If any of the excellent knowledgeable folk on here can confirm if I need a resistor to make it work with a Slick Magneto and G3X touch I'd welcome comments.
Hi Nigel,

Just follow the guidance in the G3X Touch Installation manual and you will be fine. Use a 3 conductor shielded wire, ground the shield at the GEA 24 shield block, and don't add any external resistor regardless of what you might read on the internet!

I have had a T1A9-1 wired this way on my Slick magneto for over 10 years and it always works perfectly.

TachSensorWiring.png

Steve
 
Hi Nigel,

Just follow the guidance in the G3X Touch Installation manual and you will be fine. Use a 3 conductor shielded wire, ground the shield at the GEA 24 shield block, and don't add any external resistor regardless of what you might read on the internet!

I have had a T1A9-1 wired this way on my Slick magneto for over 10 years and it always works perfectly.

View attachment 17477

Steve
Thanks Longeze that’s exactly how we have it installed which is why we’re stumped for why it’s not registering on the G3x touch display.
 
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