Points ignition causing alternator damage?

Hey all,

I have a '49 Farmall M that came to me converted to 12v (stock 6v starter and pushbutton start switch, Delco 10si alternator, IH ignition with can-style coil and resistor, copper wires). I keep burning out alternators, and I wonder if the points ignition (or the RF coming from it) may be damaging the alternator.

I found that the previous owner had wired the BAT terminal of the alt. to the ammeter, but rather than having the wire from the other side of the ammeter to the battery, he had them both on the same post. Eh? I swapped the battery wire to the opposite post, and of course, the ammeter went full-range. I plan to replace it with a 60-0-60 ammeter soon.

The second thing I found was that he had neglected to wire ANYTHING to the regulator- no sense lead, no excite wire. Nothing! I found this out after I kept burning out coils (and then resistors, after I learned a thing or two about 6-to-12v conversions), as the alternator was putting out who knows how many volts, unregulated. I say "who knows how many" because I can't actually get a reading on the volts, since the plug wires put out so much RFI all my voltmeters go wonky.

I replaced the alternator with a known-good 10si from our old '82 Jeep CJ-7, and in spite of getting it all connected correctly, it too was dead in short order (regulator again). Could the ignition be damaging the regulators? BTW, no diode, idiot light or resistor in the coil positive lead, just direct from the ignition switch to the coil.

When I replaced the alternator, I also replaced the can-style coil and resistor with a Ford TFI e-frame coil, which is rated to handle a full 12v without a resistor. With this coil, can I switch to spiral-core or carbon-core wires without degrading spark performance?

Ah, the joys of fixing other people's screwups! Thanks for any assistance.

Nick

If the 10SI is wired as a three wire system, With #1 spade terminal connected to the ignition switch through a diode in the wire (with the white band on the diode toward the alternator), it should not toast the alternator.

The #2 spade should connect to the Bat terminal on the alternator (short wire)

A static suppression capacitor can be put on the wire going to #1 terminal as well, with the lead to the capacitor connected to the terminal along with the diode wire.
If it is a one wire alternator system, all bets are off.

Magnetic suppression wires (wound wire core on a fiber bundle) work well and have very low resistance. But graphite wires will also work.
Jim

Are you connecting the battery Positive or Negative ground?

Normal Delco alternator must be Negative Ground, Positive ground will toast the alternator.

If wired to the points side of the coil yes it can/will cause an alternator to dies because every times the points close it would in turn ground the alternator. If hooked to the ignition side of the coil it will not hurt a thing since it doesn't know it it hooked there instead of at the switch. Electrically speaking it does not matter where you hook it up as long as it is in the switch side of power and is switched on and off when ever the switch is turned on or off

"The second thing I found was that he had neglected to wire ANYTHING to the regulator- no sense lead, no excite wire. Nothing! I found this out after I kept burning out coils (and then resistors, after I learned a thing or two about 6-to-12v conversions), as the alternator was putting out who knows how many volts, unregulated."

Is there such thing as a 10si that uses an external regulator? Ive never heard of one, so if your wiring in a regualtor, theres the problem! Second thing is if your buring coils, you definatley have something wrong....

@JohnM: No, it's your usual 10si with the internal regulator, but as for the two terminals on the regulator (voltage Sense (#2 terminal) and Excite (#1)), NEITHER was connected. In the absence of any voltage to the Excite terminal, it was behaving like a one-wire, and requiring high RPMs to start charging... in the absence of any voltage to the Sense terminal, it was essentially pegged to the max of its output, thinking the battery was so low it could not be 'seen', and so should be charged.
After I corrected it, it still overcharged the battery and blew up coils, so I changed it out for the one from the Jeep (also where I got the TFI coil). Now the Jeep's alt is dead too, hence my post.

@old: No, once I figured out the issue with the regulator terminals, I connected the Excite lead (#1) directly to the off-on ignition switch by the driver's right shin, NOT the coil OR the distributor.

@RVirgil: No, the tractor came to me Negative ground, as it should be for a Delco 12V conversion.

@Jim: Thanks for the info re: diodes and plug wires. I've completed an order to our YT parts store for an ignition condenser (separate issue) and the Pertronix wires. The next time I am in town, I will pick up a diode from "The Shack"... or is an 'idiot light' a better idea? From the look of posts here, people seem to go back and forth about that one, I hope that was not a "Chevy vs. Ford" type of question.

Back to my original concern: [i:4778170b75]Assuming everything is wired correctly[/i:4778170b75], is it possible for the RFI of unshielded copper wires, or the surge of a points ignition, to somehow damage the alternator?

1) Think of the battery as a big capacaitor or an electron bank i.e. a BUFFER OR SHOCK ABSORBER so a standard correct wired points ignition (or an elec ignition) shouldnt be the cause of alternator damage.

2) If an alternator lacks a voltage reference (sense) it may be damaged as it may over work and draw excess current.

3) On Delco 10 SI alternators I recommend the use of a 10 ohm current limiting safey resistor in the excitation circuit VERSUS A DIODE like most use. Also an incandescent idiot light is great cause it serves two purposes, its a current limiter PLUS it works as a non charge indicator (Idiot Light). Some even go so far as an idiot light in paralell with a resistor as a safety backup in case the idiot light opens. HOWEVER I dont see the fact it lacked one altogether as the cause of failure, Ive seen them with no diode or resistor that lasted n lasted n still working

4) Resistor suppressor plug wires are to reduce RFI interference and I see no need for them in stock points ignition systems, especially if its a magneto where Id use wire core wires,. HOWEVER in some high energy electronic ignition systems they actually prefer some degree of resistance and/or inductance in the HV secondary and do in fact recommend use of supressor wires.

5) If the coil is rated for 12 volt use (versus 6) then no external series ballast is needed as in the case where the old 6 volt coil is used after a 12 volt conversion

CAUTION if youre using points, you may wanna check the primary resistance on that TFI coil you mentioned as some (not all) coils used on high energy or elec ignitions may draw much more then 4 amps and if so your points will burn prematurely!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Hope this helps

John T

A one wire , self exciting, alternator is designed to have only the one wire connected to the output terminal. If that is what you started with and it was overcharging there was a problem in the alternator. Three wire alternators with Delco regulators are designed to not charge if there is no voltage signal on the sense terminal even if there is voltage at the excite terminal. Voltage is needed at the sense terminal to turn on a transistor to allow the voltage from the excite terminal to get to the brushes. Aftermarket regulators may be designed without this "extra" transistor so they may overcharge without a voltage on the sense terminal.

A 10 ohm 10 watt resistor, a diode, or a idiot light (not an led) all work equally well.
Your choice. Jim

In each case, it is to keep the ignition from remaining in an "ON" condition from current backfeeding the coil. This keeps the tractor from shutting off. If an alternator internal regulator failed (shorted to ground)the resistor or idiot light would prevent excessive current flow th the alt through the ignition wire. I have never seen that happen though, Jim

@Owen: No, this was not a one-wire, I said it ACTED like one. As I said previously, it's your usual Delco 10si, THREE WIRE alternator. I was not, however, aware that the alternator should not put out power in the absence of voltage on the sense lead... further proof that the first alternator in question was truly FUBAR, as it was indeed doing some overvoltage damage. Thanks for that info!

@JohnT: Thanks for the info re: idiot light (and resistor) vs. diode, I'll go that way instead. I've been meaning to go to the electric bits store to pick up a project box anyway, into which I can put an ignition switch and a few gauges (voltage, etc). I'll put the light and resistor in there.
Also, thanks for the suggestion of testing the coil- being rated for 12v doesn't mean much if it's still burning points! I'll check that out today.

Thanks to all for your help! I've got an alternator rebuild kit on the way, as well as the condenser, wires, and some other stuff. I'll try to remember to let you all know how it goes once it all gets here.

Nick

Here is a PDF file of the service manual for the alternator.

http://www.autoelectricservice.net/images/Delco_10SI_Technical.pdf

It contains information on how it works, testing, and repair.

So, I replaced the copper wires with the spiral-wound wires last week, and also replaced the condenser and points in the distributor. I re-timed the distributor to #1 TDC, or just slightly after (as per the owner's man), and got the old girl fired off. I had to play around with the carb mix, as she didn't want to rev up, but kept backfiring and burbling through the oil-bath air filter. What a mess that made! I got it going though, and she sounded better and started faster than ever she did when we first got her.

Today I rebuilt the alternator, needing only to replace the regulator. I replaced the diode trio and brushes at the same time, just as a matter of course. Since I had the DVM out for checking the old rectifier and diode trio, I checked the coil's primary resistance. Hold on to your hats: 0.8 ohms!

By comparison, an old can-style coil from one of the Jeeps measured 1.5 ohms on the primary, and the resistor mounted to its bracket also measured 1.5 ohms. Combining them gives 3 ohms, which, at 12v, will net only 4 amps, whereas I'm pulling MORE than 12 amps through the points! Yikes, no wonder the condenser and points were trashed!

So, back in goes the old coil and resistor, and the admonition is reinforced: if it ain't broke, don't fix it. I was just trying to use what was on hand, fie on me for being a cheapskate. I've got the new plug wires, that should help, and with the alternator charging again (presumably; I haven't run the rebuilt unit yet), I'm off and mowing.

Thanks to all for your help!
Nick

Long-term review: The alternator with new innards is still charging just fine. I still have not replaced the ammeter, but the charge rate has caught up to the battery life, so it rarely rises over 10A.

The old coil and resistor are doing well with the new wires, and since I re-timed the engine (by ear rather than by notch position), it starts quickly, runs well and pulls strong.

This winter's project: Low coolant + foamy oil = water jacket breach. No oil in the coolant, that's good. Head gasket or cracked block? We'll see.