Hot Coil and High Alternator Output
 

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 -

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

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.

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

Bill

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.

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

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?

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).

hanley, I've ratcheted my alternator back down so that I am seeing 14v at the battery posts. :D - 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. :eek: - 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.

If you ask why A4rians still flock to electronic ignition that is easy - we don't want to deal with changing points every year :D. 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).

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

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.

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.

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,,

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...

Neil, in your Ignition System Theory tests are you including Voltage at the + coil with your coil temp?

It would be interesting to know if there was a correlation between the two.

I'm suspecting that for a range of values there is a relationship.

Yes, primary coil input voltage is a datum but I'm not varying it in my theory or testing.

It's pretty well accepted around here that reducing the primary input voltage reduces coil temperature. Some are achieving this with a ceramic ballast resistor ahead of the coil, others are tweaking their adjustable alternator regulators down - and affecting their battery charging I believe. I'm testing a theory as to why lower input voltage has this effect or more directly, are we making changes that don't really address the issue? That is, does the end justify the means? I intend to find out.

I've enlisted the help of three other listmates so we'll have data from a variety of installations but one thing we all have in common is Pertronix electronic ignition.

I'm not trying to be mysterious about it but there's nothing really to report until the testing is complete. Who knows, we may blow holes through the theory rather than support it but that's good information too. I'd prefer to report results as opposed to conjecture. Don and I have discussed it briefly off-list and he agrees that it should be interesting.

Stay tuned - -

Thanks Hanley, no need for apologies! Excellent point. However, my electrical system is so simple I only have one battery (I know it is heresy here). I used to have two group 27 plus a group 24 starting. But I never needed that much capacity with the type of daysailing that I do. So recently when the batteries need to be replaced I simplied it.

Going back to my altnerator issue I plan to take it to a local alternator shop in Oakland and have them check it out. I believe that the regulator is shorted out (just a guess, my knowledge of alternator-regulator operations is non-existent eventhough I have a BSEE degree from an excellent engineering school which should remain anonymous to protect its reputation.:eek:) The alternator shop has the Transpo M5-197 regulator in stock for about $38, which I believe it is a direct replacement. I will report back how that goes.

Hey Triton a EE then this formula should ring a bell as they beat it into me 30 years ago

peak volts = rms*1.414, so for your issue

19.7= 14*1.414,

since your reading 20 volts instead of 14 the diodes have no voltage drop,
hence the shorted diodes.

Steve

Triton..that m5-197 is the same regulator I have, & that price seems reasonable. A diode plate at the local alternator shop was about $15.

The only issue with that regulator is it is completely potted, so you have to remove the regulator from the alternator to get to the little adjustment screw in the back to adjust the output voltage. It is a little touchy to dial in..not tedious, but it might take two or three tries to get it where you want it. I didn't think it was prudent to adjust while running, so I unmounted and remounted mine each time and tweaked the screw in 1/4 turn increments.

What I've personally done is gotten my charging voltage dialed in at the batteries to where I want it (whereas I was WAY over-charging before..detailed elsewhere on the forum in my own failed coil thread), and as Neil noted (BTW, I am one of his guinea pigs...er..."test subjects" :D, related to providing various coil data.) - I currently have a 1.4 ohm ballast resistor blocking some voltage to the new 1.5 ohm coil, as recommended by a Pertronix tech. Additionally, I have a new 3.0 ohm coil and the old failed 3.0 ohm Pertronix coil available for testing all of Neil's various theories..I agree...it should be interesting.

[off topic]
However, I've been a bit slow in reporting back to him. We've been a bit busy here cleaning up from Lee & Irene (the insurance adjuster finally visited yesterday to discuss repairs to my damaged garage roof from Irene) & trees are either still being felled on purpose to avoid future damage, or ones already on the ground are still being cut up...just not much time for intricate boat diagnostics at present, but I'll get to it here as things slow down (yeah, right..:rolleyes: ).
[/off topic]

At any rate..I personally like the Transpo regulator...I think I just had mine set too high for a while.. :o - Hanley's recommendation to have a good voltmeter aboard to check the voltage at various spots in the circuit is key..I printed out a copy of my electrical schematic and recently notated voltages at various locations (coil, battery(ies), isolator, common post, etc.) to help with diagnostics. It helped me to lay out a picture of the charging circuit in action.

No rush on my tests Shawn. I haven't had the time to get past the first barrage either. Maybe this week. Maybe.

Steve, it's been a while and I am way out of my comfort zone here. I think you are probably right. Can you just replace the diodes in the regulator or do I need to replace the whole thing? This is just for my curiosity I plan to take the alternator to a local shop as mentioned above and have them test it out.

Hi Triton, you could just replace the diodes, but there could be other failure modes in the regulator assembly.

I would replace the whole assembly and call it a day

Steve

Wow, that is a fast response!

BTW, Steve, in addition to the orange wire that I see on Moyer's wiring diagram there is yellow a wire that hangs out of the regulator and goes through a fuse and connects (red wire after fuse) to coil + terminal. Is that a sensing wire or what is it?

Triton,

It is my understanding the diode plate & the regulator are separate 'bolt on' pieces, obviously with a little wiring going on underneath.

the two shiny parts in this picture are the diode plate (top) & the regulator (big thing with 4 screws)

http://www.moyermarine.com/forums/at...0&d=1309179531