Hot Coil and High Alternator Output

[Triton106]

On another thread I recently posted I described a sudden engine shutdown problem. I was able to trace the cause to the coil and after replacing it with a MM coil the trusty A4 came back to life. However, that still left me with the nagging doubts as to the root cause of my coil problem. Here is what I posted on the other thread -

Ok, here is the follow up. Today, armed with new coil, points, condensers, distributor cap I was ready to tackle the no spark issue.

First thing I did is to replace the coil with the backup coil I bought from Moyer Marine a couple of years ago (maybe even more than a couple). The reason I suspected that coil was the cause is because I already checked voltage on the coil primary circuit and got 12V last week. In addition, when I cranked the starter I can see the voltage drop to 8/10V.

In any case, I moved the location of the coil from the back of the engine block to the engine room bulkhead to get better access. I hooked up the wirings and turned on the starter. On the first try my trusty A4 fired right up. Great, right?

No, after running it for 15 minutes or so the coil got hot (I can still hold it, though, without having to pull my hand back). Is that normal? The old (bad) coil is oil filled (I can hear it when I shake it) and the new Moyer coil is probably epoxy filled. I understand oil filled coils run cool. Should I expect the epoxy filled coils to run a littler hotter? [Edit - correction, according to MM their coils are oil filled and actually oil filled coils are hotter because they dissipate heat better.]

What troubles me more is that I still don't know what cause the coil to break. I tested for shorts between the secondary terminal and the case and found none. The original coil has been in the boat since I bought it in 2000. Could it be age? What is the expected life of a coil? Could it be due to the electronic ignition that I installed a couple of years ago? Hmmm....

I should say that my alternator is also the original Motorola 35A. Anther forum member suggested that hot coil maybe due to high alternator output which is confirmed by my voltage testing - it shows 18-20V. So, I have spent all morning reading on possible cause and cure for high voltage output. On another thread Shawn suggested that high alternator output could be caused by bad regulators and recommended a source for a bolt on replacement. However, I when I clicked on the ASE Supply Outlet Store link I was not able to find the replacement regulator. Does anyone know another source for a direct replacement regulator for the original Motorola alternator?

Thanks!

Ray Chang
Triton106 - Alameda, California

[ndutton]

I'm in the middle of testing an ignition system theory and the initial round included measuring coil temperature. On my good running A-4 with Pertronix ignition and an oil filled flamethrower coil mounted on the engine, from a cold start the coil reached 170 degrees within 30 minutes. I'm not suggesting this is good, bad or otherwise, just what I measured.

Regarding the high alternator voltage, that could also be due to a compromised exciter connection. I suggest you check all the wires and connections related to the alternator including its mounting, that's where it picks up its ground.

As a test for the coil, you can run your engine for a little while with the alternator removed. See if it runs cooler.

And a final thought, without the proper resistance type spark plugs and plug wires the coil can overheat too.

[Administrator]

I think "too hot to touch" is usually associated with temperatures around 130 degrees, right?

Bill

[ndutton]

I've routinely measured manifold temps while running that were in the area of 130 and I'd judge them warm to the touch, certainly not too hot.

[smosher]

I responded on the other thread as the diodes are shorted.

120 F is about the highest temp you can grip for a few seconds without too much pain.

Steve

[Kelly]

Just found this on the net but I can't vouch for the source:

• too hot = 120 degrees F. (48 degrees C.) Anything above this is scalding and can damage human tissue
  
• just too hot to touch = 107 degrees F. (42 degrees C.)
  
• comfortably hot = 90 to 100 degrees F. (32 to 37 degrees C.)

My coil routinely gets "hot" as in, I can put my fingers on it but have to pull them away after 4-6 seconds. This includes an American coil, a French one, a German one and now my new Pertronix Flamethrower coil (all 3ohm, oil filled). How's that for international?

[hanleyclifford]

After going around on this matter of coil failure for a few threads we still don't seem to be able to get a handle on it. As an unrepentent user of points and condensers I have to ask what is the value and point of a high powered ignition system on an engine with 6:1 compression? We go to the trouble of increasing spark with after market coils, and then put resistance in the wires and plugs. To make matters worse we get electronic ignition modules whch increase the dwell and put a further burden on the coils. Then we ratchet up the alternator output voltage and really put the screws to the coils, which are stuck between the rock (alternator) and the hard place (increased dwell).

[sastanley]

hanley, I've ratcheted my alternator back down so that I am seeing 14v at the battery posts. - I've also switched to a 1.5 ohm coil with 1.5ohm resistor in place, following the recommendation of a Pertronix tech. (I also have a 3 ohm coil mounted and ready if needed.) I've only got one afternoon's use out of the motor...it worked OK so far.

Triton, I too have found that ASE doesn't seem to carry that regulator anymore. There is another possible source on ebay, but I haven't been able to match up the Motorola alternator's part number with a regulator just yet.

Try this ebay store - triodiode - the guy says to call him if they don't have what you need. He may be able to cross reference some part numbers to see if one of his regulators will work..I don't know enough about the subtleties of pairing alternators and regulators to make an informed opinion. He may also have a diode plate if you have in fact fried yours since you are seeing 18+v output. - Personally, I'd just take it to an alt. shop..it was the local Mennonites that brought the adjustable regulator to my attention in the first place.

[Triton106]

After going around on this matter of coil failure for a few threads we still don't seem to be able to get a handle on it. As an unrepentent user of points and condensers I have to ask what is the value and point of a high powered ignition system on an engine with 6:1 compression? We go to the trouble of increasing spark with after market coils, and then put resistance in the wires and plugs. To make matters worse we get electronic ignition modules whch increase the dwell and put a further burden on the coils. Then we ratchet up the alternator output voltage and really put the screws to the coils, which are stuck between the rock (alternator) and the hard place (increased dwell).

If you ask why A4rians still flock to electronic ignition that is easy - we don't want to deal with changing points every year . There are so many maintanence and upgrades to do on every sailboat if I can eliminate one I would. Beyond that Pertronics Ignitors seem to have the endorsements of Moyer Marine and Indigo, two of the foremost authorities on A4. I think the cause of my coil failure is more likely due alternator than electronic ignition. I switched a couple of years ago to electronic ignition and never had problems with it until now (and still no problems with the Ignitor).

[Mark S]

After going around on this matter of coil failure for a few threads we still don't seem to be able to get a handle on it. As an unrepentent user of points and condensers I have to ask what is the value and point of a high powered ignition system on an engine with 6:1 compression? We go to the trouble of increasing spark with after market coils, and then put resistance in the wires and plugs. To make matters worse we get electronic ignition modules whch increase the dwell and put a further burden on the coils. Then we ratchet up the alternator output voltage and really put the screws to the coils, which are stuck between the rock (alternator) and the hard place (increased dwell).

All good points (pardon the pun!). On the one hand, once the engine is properly timed and with a cap and rotor change every year, the spark is consistent and steady, the ignition is maintenance free and suffers no steady decline with deteriorating points, and the engine runs cleaner. On the other hand, when it fails it fails completely. Like most things, I guess it's a matter of taste.

Mark

[hanleyclifford]

If you ask why A4rians still flock to electronic ignition that is easy - we don't want to deal with changing points every year . There are so many maintanence and upgrades to do on every sailboat if I can eliminate one I would. Beyond that Pertronics Ignitors seem to have the endorsements of Moyer Marine and Indigo, two of the foremost authorities on A4. I think the cause of my coil failure is more likely due alternator than electronic ignition. I switched a couple of years ago to electronic ignition and never had problems with it until now (and still no problems with the Ignitor).

If I seemed to be arguing against the use of electronic ignition, I apologize. These ignition systems are a proven workhorse and are rightly endorsed and sold by both Moyer Marine and Indigo. What troubles me is the use of such systems and the use of big alternators in the absence of accurate voltage control. My point seems to be this: If you have electronic ignition and a big alternator you are well advised to have a strong handle on voltage monitoring. This means a quality digital voltmeter that reads to hundredths of volts - like the Blue Sea models - not the multicolored analog toy sold by SW.

[smosher]

I have the 55 amp ALT from Moyer and it has a voltage sense lead which I connected to the common connection on my battery switch.

This accounts for the voltage drop in the lines and the battery never goes above 14.2

[hanleyclifford]

I have the 55 amp ALT from Moyer and it has a voltage sense lead which I connected to the common connection on my battery switch.

This accounts for the voltage drop in the lines and the battery never goes above 14.2

But what the coil wants to know is - what are you feeding me at coil+, running and cruising. If I had electronic ignition and was only able to read voltage at one point, coil+ is where I would read it.

[smosher]

Ahhhh, good question, I'll have to measure it, I was concerned about charging the batteries and never measured at the coil.

Good point though,,

[roadnsky]

I'm in the middle of testing an ignition system theory and the initial round included measuring coil temperature. On my good running A-4 with Pertronix ignition and an oil filled flamethrower coil mounted on the engine, from a cold start the coil reached 170 degrees within 30 minutes. I'm not suggesting this is good, bad or otherwise, just what I measured.

For what it's worth...
Back when testing my Hot Facet Pump, at a Laser Temp reading of 110-115° it was still comfortable to touch. Just approaching "hot".
120-125° I could touch it, but not long.
Above 130° was uncomfy.

Not true science lab test conditions, but closer to our situation with laser guns and engine surfaces maybe?

Neil-
I've "shot" my coil a few times this summer too.
(Flamethrower, Pertronix EI, Engine mounted)
Average temp is around 170° with a top temp of 185° so far.
Given my environ, it might be the high end of the fleet's scale.
Just though I'd throw that out to you for your science project...