RetISP

Im reaching out to the substantial knowledge base of this group. My car is a 66 convertible, base 327/300 with Powerglide and factory A/C. It is the original engine. The car was completely rewired three years ago and is currently running a Pertronix ignition system. The alternator has a built in regulator so the voltage regulator and the ballast resister have been bypassed. The alternator is showing correct voltage output. The car has been set to factory tune-up specs and runs very well. The problem is something is burning out coils and causing my battery to overheat and boil out the water in it. The problem is intermittant and until three days ago the car had run fine for over five months and approximately 500 miles since the last ignition coil got too hot and quit working. Before that I have replaced two batteries and at least four coils over the past year and a half. I have checked and cleaned any and all ground connections but they all looked pretty good and unlikely to be the culprit. I have not noticed the ammeter reading any surges, but it’s possible I could have missed it while driving. My first thought is it could be the alternator is defective, although it is relatively new, and only about two years old, but my mechanic tested it and he says it is putting out the correct amperage.

Any suggestions on what could be causing the excessive voltage

Thanks in advance

Mark

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Duck916

My guess is that the alternator is putting out too much voltage--that's the first thing I think of when a battery is boiling off its electrolyte. You say the alternator output is correct, though. Was that checked over a range of RPMs? What was the output voltage at idle and, say, 2500 rpm?

65GGvert

Measure with a voltmeter across the battery with the engine running and post back what you get. Rev the engine and see how much the voltage changes.

thoyer

At what voltage?

As the previous posters have mentioned it sounds like an alternator issue. The alternator may test good on the bench but when running for a period of time under a hot hood it could have issues regulating the output voltage.

Besides connecting a volt meter up and driving it for a while (try different loading as well, lights on, lights off, high beams, etc....) another test would be to swap out the alternator - any reason you went with a one wire alternator vs the original style with the external regulator?

Tom

dplotkin

65GGvert asked you measure voltage across the battery and how it changes as you rev the motor. Until you know that answer every answer is a guess.

Dan

TokyoMark

I could be in error....but thought you still need the ballast resistor when you go to a alternator with the built in voltage regulator. This drops the voltage to the coil when the key goes to the run position on the ignition switch. Could this be why you are burning up coils...to much voltage without the ballast resistor?

dplotkin

Until you diagnose your problem you just don't know.

Dan

GaryC

You've stated that the engine is “currently” running a Pertronix ignition system. Was it confirmed that the primary coil resistance was within specifications? Part of your diagnosis should be to measure this resistance. If this resistance is less than 1.5 ohms, then you should not be removing the ballast resistor. This could cause the coil to burn out.

To me, it makes no sense to troubleshoot for a defective part, if the system is not configured correctly. This should be done first. If the system is correct, then you should check what may not be working correctly. e.g., alternator supplying too much voltage.

GaryC

John S 1961

Boiling batteries was always a symptom of the diodes failing and you start getting AC voltage to your battery. Swap in a spare alternator and see if that does it.

dplotkin

Alternators have very little to do with primary current flow through the coil. It is mentioned above that primary resistance should be known. I agree. However when an overcharging event is suspected the first and easiest thing to do is rule it out with a 2 second test with a DVM across the battery.

Much of the problem with Pertronix beyond its built-in unmitigatable risks for sudden failure is a user failure to follow instructions. I don't know a lot about Pertronix and will not use it. However I have learned that folks sometimes wire them with the module in the circuit with the ballast rather than or with the coil. The OP should read carefully the instructions that came with it or if not find the model & look up the instructions on line.

There is nothing unadvisable about reading system voltage across the battery first and even once in a while. It's always good to know the basic parameters of your car, broken or otherwise.

Dan

ChrisBlair

Sometimes there's very good reason that an owner can't do what seems the obvious next step or take even the best advice before something else. Plus it's the Silly Season now so we need to give the guy a chance. If 65GGvert can't diagnose this thing, then it's not possible to diagnose. And they are all possible.

Vega$Vette

Had the exact same problem on a 64 last year. Over voltage blew out the battery, the electronic ignition module and the Retrosound radio.

Did all the trouble shooting and testing, changed the voltage regulator twice, changed the alternator. Thought is was fixed. No joy. Concluded it must be a wiring issue, original wiring. Put off rewiring the car and went with a single wire alt for simplicity. It's been fine since then.

Another thing for the OP, although probably checked already. Are you running the correct coil as spec'd by Pertronix for your application? And bypassing the ballast resistor?

RetISP

First, thank you everybody for your input. I was finally able to to out to the garage and run some of the tests:

Battery test with car off: 12.35 volts

Battery test after two minutes with headlights on then starting car, initial drops or just a fraction of a second then shot right up to 14.25.


Alternator test:

Car running, battery indicates 14.64
Car running with load: 14.48
Car off: 12.93
Negative battery terminal to alternator case while car running with headlights, radios and blower on: .01
Positive terminal to Battery post on alternator: .25

Accelerating throttle while parked did not show any increase in alternator output.

Clarifications:

The ballast resistor is not connected at all and there is nothing connected to it. Pertronix recommends not using a ballast resistor with their Chevy system.

The alternator with a built in regulator was recommended by my mechanic as it eliminates something else that could fail (voltage regulator). Since most cars have had the same set-up since the seventies, it seemed like a good suggestion.

I know the Pertronix system has its doubters, but my car at least seems to run very well with it. It was installed per manufacturer instruction by my mechanic who has installed many of them.

The coil that got too hot was a MSD Blaster 2 Coil designed to run without a ballast resistor. It’s primary resistance as stated on its box is .7 ohms. I will point out this coil had been installed since late June and had not had any problems, after initial install I checked it periodically after summer drives with an infrared temp gauge and it never registered hotter than the surrounding block area. Keep in mind both the coil and the battery evidently got too hot, so it is not necessarily just a coil issue.

Again, any further suggestions to this problem are welcome.

Mark

R66

What was the last change made to the car's electrical system prior to the first coil / alternator failure? How was the voltage regulator wiring modified to use the internal regulated alternator? -or- Did it start after the wiring upgrade 3 years ago? Did it start after installation of the Pertronix or coil? - or- Did you add any accessories like radio, A/C, cruise, etc.? Have the original radio capacitors been removed?
Have you inspected all wiring and harnesses in the ignition / charging system for signs of overheating? If the charging system is burning up the battery and coils, it may also have damaged the wiring in a non fused circuit like the ignition system.
The EEs may be able to confirm that an intermittent ground in a device or wiring will cause the alternator voltage / current to swing to maximum which could overcharge the battery and ignition system.
Just thoughts, not worth anything.

Tampa Jerry

Your car has an internal alt. My daily driver experienced the same problem. I took it to an old school starter and alt. shop. The alt. worked fine at certain RPMs, but at other speeds it ramped the voltage up to 17 volts. I believe the rectifier was changed and that corrected the problem. Good luck. Jerry

John S 1961

Exactly Rectifier equals Diodes. Bad rectifiers sends AC voltage through the system. you get a boiling battery..

RetISP

Thanks for the information gentlemen. I assume overcharging by a bad rectifier would also cause the ignition coil to overheat and fail?

Sounds like I may need to replace the alternator.

dplotkin

I don't think so. Let's review:
Battery test with car off: 12.35 volts

Battery test after two minutes with headlights on then starting car, initial drops or just a fraction of a second then shot right up to 14.25.
Alternator test:
Car running, battery indicates 14.64
Car running with load: 14.48
Car off: 12.93
Negative battery terminal to alternator case while car running with headlights, radios and blower on: .01
Positive terminal to Battery post on alternator: .25
Accelerating throttle while parked did not show any increase in alternator output.

Those voltage readings look fine. The alternator is holding its output to just about 14.5 volts, perfect. These readings will vary based on load, ambient temperature, battery state of charge (and health) and alternator RPM. This is not an overcharging alternator and I think you can put the charging system aside as a participant in your problem.

Over-voltage can kill items like light bulbs and capacitors. But its too much current, not voltage, that creates heat and burns conductors such as the primary windings of the coil. The ballast resistor or ballast wire is used on 12 volt ignition systems to limit primary current through the coil which would otherwise overheat and hasten the demise of the contact surfaces of the ignition points.

Your problem is too much primary current. Alternators cannot cause that problem. Only too high a current flow through the primary will do that, and only the wrong coil or the wrong resistance value in the primary circuit can be responsible.

Your best course of action is to thoroughly understand what the Pertronix module currently residing under your distributor cap and the specified coil requires for primary resistance, if any, and provide that.

Dan

GaryC

Dan’s comments go along with my comments about the primary circuit of the coil. In your post, you stated that “a MSD Blaster 2 Coil designed to run without a ballast resistor”. This is only correct in certain setups. The manufacturer states that a ballast resistor is required in other setups, such as: points or electronic ignition conversion kits (Pertronix). As you have stated, the primary resistance of the MSD Blaster 2 Coil is .7 ohms. Pertronix states that a ballast resistor is required if the primary of the coil is less than 1.5 ohms. I still think that your ignition circuit is not set up correctly.

This may not solve your original issue of burnt-out coils and overheated batteries, but I don’t think your ignition circuit is set up correctly.

GaryC

Dan Hampton

No wonder the original point/condenser setup looks better with every passing thread dealing with Pertronix.