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582 Tacho

in General Tech Discussion 13 years ago
Can anyone recommend a good 582 Tacho at a reasonable price... I was looking at getting a tiny tach but would like a round needle gauge... also don't really want to replace it with a top dollar tacho only to find it was something else causing the problem but still prefer to use the existing connections rather than running new wires in with the tiny tach (or something else).

BACKGROUND I have just purchased an aircraft and had some wiring issues on all gauges, I seem to have sorted some off them just by jiggling a few plugs (will do a better job of isolating the problem later). But the tacho is still useless above idle. It will read at idle but then just sits around 3-4grand or less occasionally surging up...

Thanks in advance :)

  • Re: 582 Tacho

    by » 13 years ago

    Check your grounds,,,all of them and clean them, make sure there to bare metal and that the connector is clean, as a rule of thumb 80 to 90% of the time it's the grounds that are bad.
      
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  • Re: 582 Tacho

    by » 13 years ago

    Hi Ted,

    Great thanks I will go over and check them, you are almost definitely on the money I think, just got in from a fly and the temp gauge started doing some very weird things today as well... must be an earthing problem :lol: Thanks Ted Excellent advice!
      
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  • Re: 582 Tacho

    by » 13 years ago

    I located 'a' ground problem but this only fixed water temp and EGT gauges.

    The Rotax Tacho fitted to this aircraft (Austflight Drifter) is probably the original... (circa 1994) It is connected via the grey wire and a green wire. The routing of the green wire appears to go back to the engine and 'appears' to go back to the magneto ?? I can not really isolate where it goes or grounds with out taking the whole loom apart... trying to avoid that for the moment...

    Anyway I just substituted the green wire for a separate independent ground and the tacho reads identically (badly and incorrectly) as when the green wire is attached. Surprisingly (for me at least) when the green wire (or grey) is disconnected from the tacho the electric start will not turn over (though volts showing on voltmeter from batter). Is that normal?

    If I measure volts at the grey wire tacho end what should I expect to see? What about at the Regulator/Rectifier?

    Thanks
      
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  • Re: 582 Tacho

    by » 13 years ago

    Damien,

    The grey wire goes to the tach and there should be a wire going from the tach to ground. The green and white wires from the mags go to the ignition modules. If the battery is fully charged, the engine should start even if the regulator is not working. Easy way to check the regulator is to check the battery voltage with the engine off. It should be about 12.5V. With engine running, it should be 13.5 - 14.5V.

    I think Ted is right. Sounds like you just need to check and clean all your ground and hot connections.

    There is a resistor in the grey wire which could be bad. On older engines, it was mounted inside the magneto housing. At some point, Rotax moved it outside due to failure from heat and vibration when mounted inside. If it is bad, and it's inside the case, just bypass it or remove it and put a new one in the grey wire outside the case. Some tachs don't even require this resistor.

    Bill.

    Bill.
      
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  • Re: 582 Tacho

    by » 13 years ago

    You should see 15-20 volts AC between grey wire (tacho tap) and earth (engine block). Incidentally, throwing a mag switch will drop this voltage to ~3 volts, which can cause your tacho to mis-read when checking mags.

    The rectifier/regulator is fed from 2 yellow wires -- from memory, you should see about 30 volts AC across those at 3000 rpm. FYI, the "lighting" winding on the magneto, which feeds the reg and charges the battery, is electrically separate from the 2 "charging" coils used by the CDI ignition (which is what the tacho is tapped into).

    I've just spent many hours re-wiring my 582's loom, due to the original wiring being done by an auto electrician who didn't know to run an earth bus. Ideally, a single earth wire should be used, attached to the engine block, and frame, at one end, and running through the loom to the console instruments. Everything should get earthed onto this bus wire, not tapped onto the frame at various points. The battery's negative terminal should bolt onto the engine block (not run through the earthing bus).

    Yesterday I finally fixed a problem with my water temp gauge, which was (intermittently) reading weird, e.g. turning on the fuel pump cranked the temp reading up 25 degrees! Diagnosis: grounding fault. Connecting a jumper wire directly from the sensor to the gauge earth terminal cured the problem, so I re-wired the sensor ground wire and console earth bus directly to the engine block -- it's now working perfectly.

    Cheers,
    Richard
      
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