582 rev counter playing up

[sandman]

I have a rotax 582 with an aviasport tacho and is under reading, I have checked with other tachos and all seem to do the same thing. I checked the ohms from the grey wire from the stator and it reads 38ohms which some say that's ok for the new stators on the 99 model ( 35-40 ohms ) where as the grey head was ( 30-35 ohms ). The stator is new. The tacho originally worked for about 3 hours on a 4 hour flight then dropped back to 800-900 rpm, aircraft has new stator all new wiring and am about to replace the powermate regulator with a new one, anyone got any ideas what it could be?.

 

 

[cscotthendry]

There is another thread in the forums on Rotax tacho probs. You could try some of the remedies posted there.

 

 

[sandman]

Have checked those other forums but my tacho is under reading and have checked with 3 other tachos, When at cruise 55 kias tacho reads steady 2000rpm but when I come back to idle power it will read from 3000rpm down to 2000. I am replacing the regulator as it was one of the earlier ones, process of elimination I guess.

 

 

[Ayecapt]

Hi make sure that the main ground cable that connects your engine casing to the battery are all clean and tight.

 

And the instrument panel is correctly earthed . Often when odd things happen electrically it is a poor earth.

 

Earth conductor lugs must be bolted so that there is no paint under the lug face at all. We all know paint is a insulator but it also has some thickness . So any paint under a lug will stop good contact being made . Remember scratched paint is just ribs of plastic insulator under your lug. its very easy to believe that it will be right because that big bolt will scratch or gouge its way to make a good contact but at low voltages it cant be relied on to do so in the long term . And any voltage drop here is a large percentage of the battery voltage .

 

I've had a tach where the entire internal mechanism ie the circuit boards and meter movement were working loose , that is the internal nuts holding it together were loosening.

 

It of course was doing crazy things as the circuitry connected and disconnected.

 

I got onto that one because i noticed that the dial seemed to be off horizontal.

 

Sort of like it was rotating in its case which it actually was. However you have tried other tachos.

 

 

[sandman]

Just an update, the tacho is working correctly, cause is still unknown but figuring out what has changed?.

 

 

[Blueadventures]

Chris

 

If not yet done check that the female connection from the pulse line (engine sender to guage) to the pin on the back of the guage is not broken inside the heat srink. They can break and be held in contact by the heat srink an be hidden from view. I have had this intermitant tacho problem in the past. At first thought it was a ground connection problem then discovered the connection end broken.

 

Cheers

 

Mike

 

 

[sandman]

Has anyone checked the paper diagram on the back of their aviasport tach, the pick up wire should be on the left hand side lookind at the wire pins not the right as the diagram indicates.

 

 

[sandman]

Just found this on the aviasport website so please disregard the last post, cheers.

 

- The instrument is basically an AC unit,

 

therefore not need to coordinate polarity (AC).