Jump to content

advice on when to change mags


rbridges

Recommended Posts

going through my annual.  Around 1050ish hours SMOH on my O360.  Slick mags, both seem to be running great.  I had them inspected 100-150 hours ago, and everything looked good.  Anyway, my harnesses are looking pretty ragged, especially near the spark plugs.  IA recommended changing the harnesses, and then he started asking about the mags.  I'm really thinking to leave the mags alone.  I have two, so I'm thinking I've got the redundancy if one starts to give me issues.  I'm not one to defer squawks, but I'm having a hard time replacing a mag that's been recently inspected and running great.

Link to comment
Share on other sites

Replace all the plugs and the harness, inexpensive items compared to other stuff.  There may be some infant mortality issues but there is plenty to back up and if you have an engine monitor all the better....

Mags should be fine.....I stager my inspections as well on the mags.  Then at overhaul get all new stuff again.  They will be 1000 hours old anyway....

  • Like 1
Link to comment
Share on other sites

Thanks.  I thought it may be a little optimistic to hope they'd make it to overhaul, but I'll keep my fingers crossed.  Spark plugs replaced 2 annuals ago and look good.  Maybe I'll just change the harnesses.  I kinda toyed with the idea of swapping to Bendix.

  • Like 1
Link to comment
Share on other sites

So, what can go wrong with a mag:

Points wear out and stop opening - mag quits no harm to engine or mag.

Coil opens - mag quits no ham to engine or mag.

Condenser opens - fries points weak spark, no harm to engine or mag.

Gear slips - no spark to plugs, no harm to engine.

Distributer bearings seize, strips gear, no spark to plugs, no harm to engine.

Input bearings seize - make metal in engine, lock up and damage engine gear train.

 

So you have better than an 80% chance that the mag will just quit without doing any other harm.

 

Link to comment
Share on other sites

1 hour ago, rbridges said:

going through my annual.  Around 1050ish hours SMOH on my O360.  Slick mags, both seem to be running great.  I had them inspected 100-150 hours ago, and everything looked good.  Anyway, my harnesses are looking pretty ragged, especially near the spark plugs.  IA recommended changing the harnesses, and then he started asking about the mags.  I'm really thinking to leave the mags alone.  I have two, so I'm thinking I've got the redundancy if one starts to give me issues.  I'm not one to defer squawks, but I'm having a hard time replacing a mag that's been recently inspected and running great.

Replace the harness now.  Have the mags inspected again in 350-400 hours unless they give you grief between now and then.

Curious as to why your IA would ask about the mags.  Wouldn't he see that the last inspection date on them in your engine log was 100-150 hours ago?

Steve

  • Like 1
Link to comment
Share on other sites

If the braiding on your ignition harness gets worn and frayed, they won’t stop working.  They may cause some ignition noise on your radios.  Have your maintainer do a high tension test of the individual wires and if good repair the frayed ends by trimming them back 1”.

Put the harness savings into the mags.

Clarence

Link to comment
Share on other sites

I'd be far more concerned about the mags, but an "inspection 100-150 hrs ago" is ambiguous to me. Are you referring to a 100 hr inspection or a 500 hr/5 yr IRAN? I do the 100 hr inspection annually and always comply the 500hr/5 yr IRAN. Its a false sense of security to assume since you have 2 mags you can run on one just fine. Our engines need both to run satisfactorily. Put another way, loose a mag and you're just one plug or wire away from losing a cylinder and 25% of your power. Remember 2 of those cyl's on the remaining mag are only being fired by the dirtier less efficient bottom plugs. If that doesn't concern you, consider a bad mag is going to cost you much $ and inconvenience away from home. At Savvy where we advocate maintaining  most everything on condition, including ignition wires, the mags are the big exception. With mags its best to comply with the recommended 100 hr and 500hr/5yr inspections and IRAN in accordance with L-1363-F (slick mags overhaul manual); especially with the Slick mags. 

On the other hand if the the last inspection was a full 500 hr IRAN, then you should be fine to do just the recommend 100 hr inspection each annual.  

Only at engine overhaul would we advocate overhauling or replacing the mags. Economics typically dictates whether you overhaul or replace them when the time comes. But as long as you can economically get through the 500hr IRAN every 500 hr or 5 yrs, there is no need to replace or overhaul them.

Edited by kortopates
  • Like 2
Link to comment
Share on other sites

Replacing the harness is pretty easy. I used Kelly, and it was surprisingly less expensive to wait a few days for them to make a set with 90° ends than to buy the tips and do it myself. The whole job is just a couple of hours, all labeled and only fits one way.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.