The tach for my 912 is giving me fits. when it reaches about 3500rpm it starts spiking toward max rpm. as I increase throttle it will finally peg out. I have checked all the connections several times and I am not winning! Has anyone else had this problem? If so how did you fix it?

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Comment by Jonathan Porter on June 9, 2010 at 1:15pm
Comment by Dennis Johnson on June 9, 2010 at 11:54am
actually the instructions were for a UMA tach and worked on the VDO tach!! I think the resistor is just a filter for hard spikes that may be in the system and should work on any tach that has this problem.
Comment by Jonathan Porter on June 9, 2010 at 3:15am
Congrats!!! I have installed many Tachs, but this must be a special specific fix. To avoid confusion for future readers of this thread it would helpful if you could post a picture of which tach we are talking about!
Comment by Dennis Johnson on June 8, 2010 at 5:03pm
Well I got the new tach from ACS. In the instructions it said that if the tach was erratic at high RPM's add a 270 ohm resistor between the signal and ground. Tried that on my original and the problem went away! guess now I have a spare tach also!!
Comment by Dennis Johnson on June 4, 2010 at 6:34pm
gave up on it and ordered a new UMA tach for the rotax. I was gone all week so I haven't had a chance to try the new one. Probably Monday. Cross your fingers for me!
Comment by Jonathan Porter on June 1, 2010 at 12:25pm
how did you get on ???
Comment by Dennis Johnson on May 23, 2010 at 10:45am
I just thought of someone with same setup here at our field. I will try to get ahold of him and see if he would mind testing it for me. thx for your help and I will let you know what I find out.
Comment by Jonathan Porter on May 22, 2010 at 12:39pm
There is the Rotax Tach itself - or ROAD or many of the digitals...

If you have somebody (a helpful somebody) with a working install of a 912 they may let you slave off of their cables (it is only a 3 connector job - so slide them off and 'hang' the tach under so that you can check on static) - or your local 'shop' may have a test rig.

If you were closer I have a spare tach here... (but the freight from Ghana kills the proposition) - why not look at Aircraft Spruce - they have lots on offer - and if the current tach is a new one it may well be under Guarantee - all options....

Let us know how you get on.
Comment by Dennis Johnson on May 22, 2010 at 10:57am
This is a new install. Looks like a new tach is where I will be headed. Connections and sender have been pretty thoroughly checked. Is there another 2 1/4" tach that is compatible with the 912? thx for the help
Comment by Jonathan Porter on May 22, 2010 at 2:16am
Is this a new install or a sudden problem? If it is a new install - try another tach - about 1 in 20 seem to have some glitch (you should check the tach accuracy against a stroboscope too, but most don't).... Second - check the grounding - there are two wires coming from the engine - one goes to the tach - one goes to ground (it matters not which one) - if the ground is poor or vibration affected it may create the same problem. Check for a broken wire or poor connection (simply look at the connection and shake it - it may break - then you can fix it!!) - again vibration could be a cause...

Finally there is the sender on the engine - take a look - but dont fiddle with it... maybe it is not well secured - unless you have experience, let the Techie reset it - I HAVE NEVER SEEN ONE OF THOSE COME LOOSE ON ITS OWN - but you never know :-) Smile and be happy - you fly again soon!!!

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