New Ignition Harness

[Speed Merchant]

I have been fighting a radio noise issue for a while. We determined it was ignition by switching the left and then the right mag. The noise was still there but not as loud. We shut both off and voila no more noise. I think I need a new ignition harness. Does anyone know the part number for the harness? My bird is a 84 201 with A IO360 A3B6D. 
Thanks

Curt

[Pinecone]

Maggie's Harness.

[EricJ]

+1 for Maggie Ignition Systems.    Also check that you don't have one or more plugs out of resistance spec, i.e., >5k Ohms..

https://www.maggieignitionsystems.com/

[OR75]

Maggie Harness is good should you decide to go that route. Although the lead time can be long.

you will need to send your old harness.

Are you sure it is the harness ? is it in that bad a shape ? shield in bad shape ??

And what do you mean by shutting both off and voila ? the engine is still running ??

[Speed Merchant]

At 5000 feet I shut both mags off and the radio sounded great.  With the mags shut off no radio noise. So I think it definitely an ignition problem. I had the mag rebuilt and during the rebuild most components were replaced with new. The harness is at least 14 years old and was folded back on itself and tied with stay straps because two of the cables were too long.The shielding is coming loose at the nuts that attaches the cable to the spark plug. I think the harness needs to be replaced. I am running out of things to change. I have been to see two avionics specialists. So far with little improvement. Hopefully this will fix it. Thanks for your posts.

Curt

 

[LANCECASPER]

On 1/2/2025 at 11:03 PM, Speed Merchant said:

At 5000 feet I shut both mags off and the radio sounded great.  With the mags shut off no radio noise. So I think it definitely an ignition problem. I had the mag rebuilt and during the rebuild most components were replaced with new. The harness is at least 14 years old and was folded back on itself and tied with stay straps because two of the cables were too long.The shielding is coming loose at the nuts that attaches the cable to the spark plug. I think the harness needs to be replaced. I am running out of things to change. I have been to see two avionics specialists. So far with little improvement. Hopefully this will fix it. Thanks for your posts.

Curt

 

If you have Champion Spark Plugs I would check there first. As @EricJ mentioned they go out of spec on resistance soon. Testing the resistance is easy and almost every time I've checked a Champion plug that had been in over 200 hours it was out of resistance.

[Marc_B]

15 hours ago, OR75 said:

you will need to send your old harness.

I ordered from New Horizons / Maggie when I was installing a Surefly.  They just needed info for my engine, mag harness cap type, and airframe.  I didn't send them my old harness and the new one fit perfectly.

[EricJ]

14 hours ago, Speed Merchant said:

At 5000 feet I shut both mags off and the radio sounded great.  With the mags shut off no radio noise. So I think it definitely an ignition problem. I had the mag rebuilt and during the rebuild most components were replaced with new. The harness is at least 14 years old and was folded back on itself and tied with stay straps because two of the cables were too long.The shielding is coming loose at the nuts that attaches the cable to the spark plug. I think the harness needs to be replaced. I am running out of things to change. I have been to see two avionics specialists. So far with little improvement. Hopefully this will fix it. Thanks for your posts.

Curt

 

The big loop of extra lead length is because there are other aircraft that use the same harness that take a longer routing path than is available in the Mooney.   The 177RG has the same ignition and I think it uses the longer route.   You won't get shorter leads with a new harness.    

[Bartman]

On 1/2/2025 at 4:46 PM, Speed Merchant said:

I have been fighting a radio noise issue for a while. We determined it was ignition by switching the left and then the right mag. The noise was still there but not as loud. We shut both off and voila no more noise. I think I need a new ignition harness. Does anyone know the part number for the harness? My bird is a 84 201 with A IO360 A3B6D. 
Thanks

Curt

I had the same issue even after replacing the spark plugs.  I diagnosed it the same way.  A new ignition harness for my A3B6D solved the problem, and instead of some fabric-looking insulation, I now have red silicone that looks like it belongs on a hot rod.

[Speed Merchant]

On 1/3/2025 at 8:27 AM, LANCECASPER said:

If you have Champion Spark Plugs I would check there first. As @EricJ mentioned they go out of spec on resistance soon. Testing the resistance is easy and almost every time I've check a Champion plug that had been in over 200 hours it was out of resistance.

Thanks I will definitely check out the plugs,  I appreciate your post.

Curt