p-mag ignition wire resistance

[KayS]

Hi All,

i fabricated one ignition wire for my p-mag today. i did it like the manual told me and everything was looking good. but then i measured a resistance between the two coils at about 0,5 kilo ohms. i expected something near zero. do i miss here something?

thanks
Kay Stecklum

[lostpilot28]

From the P-mag installation manual - "Each lead should produce approximately 180 ohms of resistance per foot of plug wire".

How long is the wire you made? If it's 2-1/2 feet long, then 500 ohms would be good. I'm assuming you mean .5 k-ohms, BTW.

[KayS]

ups... seems that i didn't read that whole manual. mine is about 2 feet long... that explains everything. thank you.

Kay Stecklum
RV-7

[rwtalbot]

As a suggestion, write down the figures for each lead and check them every year at annual. The leads can get moisture inside and corrode over time. I wiggle the ends of each lead with the multimeter attached to look for any looseness.

This year I had two leads fail (3rd annual and just over 300 hours TT). I had noticed a very slight intermittent miss at idle. Two new leads later and the engine now starts really well - I had not noticed any degradation. The miss is gone too.

Interestingly, the failed leads were both upper plugs. I fly a fair bit of IFR and they have definitely had some water in the front. Corrosion was evident. I am investigating methods of obtaining a slightly better plug lead or use of a dielectric grease.

Richard


RV 7A - Flying