Radio Static Problem

[steve@innoviator.com]

Good Evening Mooneyspace folks,

 

Discrepancy:

Noticed radio static during run-up, after annual completion.

 

Background:

"high low volts" problem  discovered during night landing 4/10/2013 (discovered 24V landing light installed in 14V system, R & R with PMA LED Landing Light. Replaced voltage regulator, Oil Pressure system and Fuel Pressure system amplifiers, CHT and probe R & R’d….returned to service 5-11-2013 (cost $3500)

"high low volts" problem  1/13/2014 (see Annunciator Troubleshooting)

 

Radio Static Repair:

After researching Mooneyspace, several forum posts recommended checking master switch first for corrosion. While inspecting for corrosion all “male terminals” on back of switch were clean. However one “female” terminal appeared burnt at locations where previous maintenance had crimped vinyl heat shrink. The wire run appears to go to voltage regulator

 

Notes from attached photos:

1)    Burn marks common to crimped locations

2)    Discoloration of 0.25” female terminal connection

3)    No discoloration of 18 AWG wiring. (0.1 milliohms)

 

1-27-14, I will install new pre soldered AWG 18 terminal end and heat shrink to R & R wire terminal end.

 

 

Question: Has anyone else seen burnt wiring and do you know what the root cause was?

 

 

Thank You

Steve

[N201MKTurbo]

I've never seen push on terminals used on critical systems like the master switch and voltage regulator. They should all be ring terminals with screws.

[PLN_FXR]

Burnt wiring is due to an overload condition (unlikely) or a loose connection (arcing).  Good luck!

[N601RX]

Agree with MKTurbo, spade terminals usually are not used on aircraft. Also the crimp in the picture is poor. Overheated connectors is usually caused from a high resistance connection.

[cliffy]

yup wrong terminals!

[bumper]

Do you have the same radio static with LED landing light on or off?

 

You can tighten and improve the spade connections. Use a needle nose pliers to gently squeeze the rolled over part of the female connector - - don't get carried away and squeeze it too tight or it will be difficult to push onto the male spade.

 

Also, before assembly, apply some Dow DC4 or other silicone grease. This will help prevent corrosion and resistance build up by keeping the connection gas tight. Typically the reason connections like this overheat is due to resistance build up - - even with normal current flows the voltage drop and power dissipated due to resistance increasing can cause overheating as you are seeing.

 

bumper 

[jlunseth]

Hate to say it, but have you tried just switching the squelch back on? That is the first thing I notice after maintenance, switches I almost never touch that get moved.  Usually it is a push-pull on the power switch for the comm.

[steve@innoviator.com]

Thank You Folks,

Great feedback......

 

To: N201MKTurbo

I agree, and I will order a new Master Switch with terminals having screws. For a switch as important as the master switch, it should be a standard electrical practice

 

To: Bumper

I do use an equivalent to DOW DC4.  I will pay attention to Radio Static while operating the LED landing light......and report back to you.

 

To jlunseth:

Thank you...I did try the squelch switch, and it did not remedy the problem.

 

Sincere Thanks to all responses...I appreciate your insights

 

Steve

[steve@innoviator.com]

Thanks Mooneyspace Folks,

 

Radio Static problem fixed.....and no noticeable radio static during LED Landing Light on.

 

Sincere Thanks 

[DonMuncy]

What was the problem?

[steve@innoviator.com]

TO DonMuncy

See initial post 1-26-14 and attached photos

 

Discrepancy:

Noticed radio static during run-up, after annual completion.

Apparently, at some point maintenance crimped the wiring common to the Master Switch terminals..

 

Thanks

steve

[DonMuncy]

Oops, sorry.