RPM display trouble

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many
Posts: 7
Joined: Thu Mar 04, 2021 7:00 pm

RPM display trouble

Post by many »

Hi All!!
I have a problem with my IEFIS Challenger lite. I have an American champ with a C90 installed. I have connected the sensors to my RPM (one for each magnet) so it works perfectly up to a revolution of about 1300rpm. After that, the meter jumps up to 1800 for no reason. I have not touched the throttle. Then it can jump up and down until I pull the throttle back to below 1300rpm. Has anyone had a similar problem? What have I done wrong!! :o
rainier
Site Admin
Posts: 662
Joined: Fri Aug 28, 2020 7:03 pm

Re: RPM display trouble

Post by rainier »

Sounds like you have not installed a inline resistor and not selected the correct RPM sensitivity.

Typically you need a 10-40 kohm resistor inline from the magnetos. The exact value varies between magnetos and there does not seem to be an easy way to find out. Easiest is to just use a trimmer (say a 50K) and tweak it for best result.
The RDAC must have ballast OFF, filter ON, High gain OFF and adjust sensitivity with blue trimmer.
dar-maley@cox.net
Posts: 3
Joined: Tue Mar 23, 2021 3:11 am

Re: RPM display trouble

Post by dar-maley@cox.net »

I am installing a IEFIS Challenger & RDAC with a Lycoming O-540. RPM indicates 10% of actual RPM (150 while at 1500RPM). I tried moving the Ballast jumper but then got no indication. Suggestions?
rainier
Site Admin
Posts: 662
Joined: Fri Aug 28, 2020 7:03 pm

Re: RPM display trouble

Post by rainier »

What are you using as pulses per RPM in your RPM setup and what type of pickup are you using ?
dar-maley@cox.net
Posts: 3
Joined: Tue Mar 23, 2021 3:11 am

Re: RPM display trouble

Post by dar-maley@cox.net »

UMA T1A9-2 sender, 1.5 pulses per revolution.
dar-maley@cox.net
Posts: 3
Joined: Tue Mar 23, 2021 3:11 am

Re: RPM display trouble

Post by dar-maley@cox.net »

Found it. details later.
Major_John
Posts: 2
Joined: Tue Jul 05, 2022 8:59 pm

Re: RPM display trouble

Post by Major_John »

Hello gentlemen,
I had the problem with Lycoming 540, Bendix mag
First - the window was wrong
Second - it was need to adjust sensitivity
hope it will be helpful to anyone in the future
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