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henrysamson
05-24-2013, 04:44 AM
Hi,

I reported a problem with a loud squeal in my audio when my 912 is running over 4000 RPM. At least one other forum member posted the same problem and I have seen it reported on other forums. I finally figured out what was causing it in my case.

Not the ignition but the alternator. I have my alternator regulator mounted behind the panel and near the intercom. In planning the panel layout I made sure to keep all of the ignition wires on the other side but did not realize the problem with the alternator.

Rotax provides a shielded cable with two yellow wires that supplies the AC from the alternator to the regulator. The problem is that the shield ends about 4-6 inches before the regulator. I put a layer of rescue tape over the unshielded wires from the end of the shield to a point close to where they will plug into the regulator. I did this for protection because I next added a shield using self adhesive aluminum foil tape. I wanted to make sure the aluminum (although quite thin) does not work through to the conductors. The tape I used is bare aluminum on the non-adheshive side. I folded over a 45 degree triangle at one end (adhesive to adhesive). This turns the bare outside to the inside. Then I wrapped this bare portion over about one inch of the existing shield so they are in contact. Continued to wrap the tape (adhesive in towards the rescue tape) up to the connector end. Then I used several zip ties to make sure the shield end is very tight against the shield so they make contact. A meter verifies that they do. A few more zip ties along the length just incase the adhesive ever gives up and then I put the connectors back in the plug and the plug into the regulator.

Almost all of the noise is now gone! I used to have my intercom squelch set almost all the way on at 5000 rpm. Now I am just basically turning it up enough to cut out the cabin noise. I hope this solution is helpful.

Hank

Av8r3400
05-24-2013, 05:08 AM
Excellent, Hank! Thank you for sharing!

Dorsal
05-24-2013, 06:46 AM
Great work and result, really good to know!