New a4 owner hoping for some assistance

[hanleyclifford]

Since we now see that you have electronic ignition the dwell issue is settled. It is fixed maybe around 55 degrees which is way more than the points type ignition. It also means that the voltage at coil+ is even more important to know since that EI dwell is pushing a stronger belt thru that coil. Resistance is even more mandatory (if you'll pardon the expression).

[stranded-sailor]

Since we now see that you have electronic ignition the dwell issue is settled. It is fixed maybe around 55 degrees which is way more than the points type ignition. It also means that the voltage at coil+ is even more important to know since that EI dwell is pushing a stronger belt thru that coil. Resistance is even more mandatory (if you'll pardon the expression).

Resistance is always mandatory!! Sorry, had too. Lol
Coil resistance across small posts is 1.9 when set on 200 setting. Resistance from center is 8.10 on 20k setting.
Your meaning v at coil + when running correct?

[joe_db]

1.9 ohms across the coil primary is WAY low. They will burn out. You want around 4 ohms or so.
My coil is about that as-is, but if you don't have one with that much resistance you can either buy a new one that does or add a ballast resistor.
We also have the issue of the electronic ignition itself burning out, which is rare but not impossible.

[joe_db]

It just so happens our host sell the correct coil to solve this issue:

https://moyermarine.com/product/coil-with-internal-resistance-iglm_05_31/

[stranded-sailor]

1.9 ohms across the coil primary is WAY low. They will burn out. You want around 4 ohms or so.
My coil is about that as-is, but if you don't have one with that much resistance you can either buy a new one that does or add a ballast resistor.
We also have the issue of the electronic ignition itself burning out, which is rare but not impossible.

I looked up resistance values for coil and found this

a 12 volt coil will have a nominal resistance of around 1.5 ohms give or take a couple of tenths. The secondary resistance should be at least 8,000 ohms and can go as high as 12 to 13 thousand ohms depending on the coil

Is the coil for the a4 different? I got this replacement coil at a car parts place. Looked at my old one and said this one would work.

[hanleyclifford]

Resistance is always mandatory!! Sorry, had too. Lol
Coil resistance across small posts is 1.9 when set on 200 setting. Resistance from center is 8.10 on 20k setting.
Your meaning v at coil + when running correct?

Right, voltage at coil+ engine running is where the rubber meets the road. Doesn't matter how you get there. I don't like coils with internal resistance because they do not afford the opportunity to monitor voltage where it matters. The internal resistor may indeed reduce the voltage to an acceptable level but you cannot measure it, and because the resistor is in the coil there will be heat generated. Heat is the enemy of electrical devices, yet ironically most do produce their own heat.

[hanleyclifford]

It just so happens our host sell the correct coil to solve this issue:

https://moyermarine.com/product/coil-with-internal-resistance-iglm_05_31/

That coil will certainly do the job and the price is reasonable.

[stranded-sailor]

Right, voltage at coil+ engine running is where the rubber meets the road. Doesn't matter how you get there. I don't like coils with internal resistance because they do not afford the opportunity to monitor voltage where it matters. The internal resistor may indeed reduce the voltage to an acceptable level but you cannot measure it, and because the resistor is in the coil there will be heat generated. Heat is the enemy of electrical devices, yet ironically most do produce their own heat.

So as I'm trying to figure this out I'm wondering if this coil not having an internal resistor being part of the problem, or causing me a new one. I took old coil to part store and he gave me this new one. Now that I look at it, with the new info I'm gaining here, I'm seeing that it says external resistor required. Has using this coil they gave me caused me more problems due to that?

[stranded-sailor]

That coil will certainly do the job and the price is reasonable.

Thats actually 4$ cheaper than the one I got here and I'm thinking this one is wrong to boot. That's what I get for going to a part store without knowing exactly what I'm looking for!

[stranded-sailor]

1.9 ohms across the coil primary is WAY low. They will burn out. You want around 4 ohms or so.
My coil is about that as-is, but if you don't have one with that much resistance you can either buy a new one that does or add a ballast resistor.
We also have the issue of the electronic ignition itself burning out, which is rare but not impossible.

How would I test to see if the ignition is burnt out?

[hanleyclifford]

I looked up resistance values for coil and found this

a 12 volt coil will have a nominal resistance of around 1.5 ohms give or take a couple of tenths. The secondary resistance should be at least 8,000 ohms and can go as high as 12 to 13 thousand ohms depending on the coil

Is the coil for the a4 different? I got this replacement coil at a car parts place. Looked at my old one and said this one would work.

He's right; it would work - IF it had the correct resistance in front of it. In fact just about any "12" volt auto coil will fire the A4 but buying the coil from Moyer Marine takes the guesswork out of the solution.

[joe_db]

I looked up resistance values for coil and found this

a 12 volt coil will have a nominal resistance of around 1.5 ohms give or take a couple of tenths. The secondary resistance should be at least 8,000 ohms and can go as high as 12 to 13 thousand ohms depending on the coil

Is the coil for the a4 different? I got this replacement coil at a car parts place. Looked at my old one and said this one would work.

1.5 ohm coils will burn out. My auto parts place, being on an island, has 4 ohm coils for Atomic 4s, but 99.5% of them hardly understand old fashioned coils anymore. Moyer also has them

[stranded-sailor]

Ok. All good information. After tearing into this this afternoon I think its just time for a full tune up. Everything is wore some and plugs are obviously old. Coil reads good and getting power but no spark. Problem is I was hoping to leave here tomorrow night to get to a spot where I have better support. Only get the odd 24h with under 25kn winds and tomorrow nights one of them. If I'm understanding correctly this coil will work just not last as long as the right one? Maybe local parts store has cap and rotor button? And they should have plugs no problem.

[hanleyclifford]

Ok. All good information. After tearing into this this afternoon I think its just time for a full tune up. Everything is wore some and plugs are obviously old. Coil reads good and getting power but no spark. Problem is I was hoping to leave here tomorrow night to get to a spot where I have better support. Only get the odd 24h with under 25kn winds and tomorrow nights one of them. If I'm understanding correctly this coil will work just not last as long as the right one? Maybe local parts store has cap and rotor button? And they should have plugs no problem.

Local parts store might even have a resistor for you. Worth asking. 2 ohm for starters, only has to carry 2 amps max

[joe_db]

What he said. Ask for a 2 ohm ballast resistor or somewhere around that like 1.6 ohms.
Like this:

https://www.amazon.com/Aramox-Ignition-Resistor-Wear%E2%80%91Resistance-Replacement/dp/B09JWYNZ8Z/ref=sr_1_3?crid=MH3NSDFV599J&keywords=ballast+resistor+for+coil+12v&qid=1699499887&sprefix=ballast+res%2Caps%2C120&sr=8-3