Aftermarket Alternator Question

[serIIalpine]

I installed an aftermarket alternator ( with internal regulator) in my Series II a few years ago and as I very rarely drive at night what has become an issue only recently reared it's ugly head. Here's the problem: The alternator charges just fine and after a few minutes of highway driving my voltage meter shows 13+ volts. If I switch on the lights or even turn on my blinkers the voltage plummets rapidly. Down to less than 12 volts in five minutes. I had the alternator tested at Auto Zone, I realize this is no garrantee of accuracy, and they said it was OK.

What I'm wondering is this ( provided it is in fact "OK"): do I need a higher amperage alternator ot just a smaller pulley for my alternator?

Your thoughts appreciated.

By the way I followed the tech tip from the old forum to do the conversion.

Thanks

Eric

'62 SerII

 

[Pumpkin]

I installed an aftermarket alternator ( with internal

What I'm wondering is this ( provided it is in fact "OK"): do I need a higher amperage alternator ot just a smaller pulley for my alternator?



Eric, I would throw that idea into the pot for looking into. There was a thread just awhile back about pulleys. I think Paul knows all of that stuff..

Chuck

 

[mikephillips]

I doubt a pulley change will do much since alternators develope their max output a fairly low revs unlike a generator which will increase as the run faster. I would guess that you need a higher output unit unless you identify a problem in the wiring.

 

[jumpinjan]

Just because the alternator looks like it’s turning, doesn’t mean it’s turning fast enough to charge. Most alternators do not start charging until they reach 1,000 RPM alternator shaft speed. 5,000 RPM alternator shaft speed is normally required to reach maximum output.

If you’re not sure what the alternator shaft speed is, you can determine this with the pulley ratio.
1) Measure the diameter of the crankshaft's drive pulley and the alternator pulley.
2) Divide the crank shaft pulley diameter by the alternator pulley diameter. This figure would be the engine-to-alternator RPM ratio. A normal ratio would be 2.5 to 1.
For example, let’s say we have a 7 inch diameter crankshaft pulley and a 2.75 inch alternator pulley. We would divide 7 inches by 2.75 which equals 2.54 to 1. If the engine was turning 1,000 RPM we would multiply 1,000 by 2.54 which would give us 2,540 alternator RPM.
Jan

 

[RootesRooter]

If the tiny additional load from the turn signals is enough to cause these symptoms, it doesn't seem likely that it's just a matter of choosing a higher amperage alternator or a different pulley.

 

[jumpinjan]

That's a good observation. That tells me it may not be working correctly.

 

[Tom H]

Eric,

What aftermarket alternator are you using ? And can we assume that you've converted to Neg ground? I would say that most likely something is wired incorrectly.

Is the tech tip you used for the conversion still available? Exactly where is it?

Tom h

 

[serIIalpine]

I'm using what I believe to be the one refered to in the tech tip below.


http://www.team.net/www/rootes/sunbeam/alpine/mk1-5/techtips/altconv.html



Thanks

Eric

'62 SerII

 

[serIIalpine]

I'm using what I believe to be the one refered to in the tech tip below.


http://www.team.net/www/rootes/sunbeam/alpine/mk1-5/techtips/altconv.html

I reread the tech tip and found that it says that my ignition light should go out when the engine is running.

It stays on. My installation has a resistor in line as per what may have in fact been another tech tip. I believe it is there should the dash light burns out the alternator will continue to charge.

I could be wrong.

I actually don't think it's the instellation as it does charge just not with the lights on as they seem to draw too much power.


Thanks

Eric

'62 SerII

 

[Nickodell]

Eric; you say that your alternator "charges just fine," but then go on to say that the no-charge warning light stays on. How do you know that it's charging unless you have an in-line ammeter?

My feeling is that it's maybe just trickle charging; maybe 1 or 2 amps, which would not be enough to support any accessory, hence the lights or whatver you switch on draw from the battery and the voltage goes down.

As there are several different kinds of alternator with different wiring, you need to be sure everything is wired up properly and the conenctions are good. As an example, in one design there are three: one BAT, one field and one sensing. The field wire goes to the "idiot light" and then to the 'RUN' position of the ignition switch. The sensing wire either goes to the 'BAT' side of the ignition switch or the 'RUN' side depending on the application. When the ignition is in the run position the sensing terminal is energized with battery voltage and the field terminal is energized with a current limited voltage through the lamp. When the alternator starts charging, the field voltage raises and the voltage differential across the lamp reduces and the lamp goes out. The charging voltage is 'sensed' through the sensing wire and the internal voltage regulator regulates the voltage to about 14 volts.

As they say in the mpg and slimming adverts, "your results may differ."

 

[Tom H]

Eric,

Lots of good advice from Nick. Let me add a bit more. You say you wired it like this tech tip. But I guess without the Ammeter but with the Voltmeter. Is that correct? And also your installation includes a resistor somewhere. Where? Depending on where that could be your whole problem. This particular style aternator and installation does not require any resistor and if the lamp burned out I do not think the alternator would stop charging, although the article describes using a resistor if the system does not have a lamp. Lastly do you have exactly the alternator described in this tech note? It should be a Mitsubishi 14231, or equivalent, same as I have installed in my SV.

One last thought. The ammeter in the drawing is located incorrectly. As drawn it will only show current that charges the battery and willl not show current coming from the battery to the load . But since you are not using an ammeter that makes no difference. But in case you ever DO install an ammeter be sure to locate it correctly. This has been discusssed several times on this forum.

Tom H

 

[jumpinjan]

If the shunt blows (for some reason) with ALL the loads passing through it, your car is dead. If it blows with loads to just the battery, it will still run on battery only. Which would you want?
(One surely doesn't want to wire an airplane like that )
Jan

 

[Drnobeam]

I installed the same alternator from the article and it's been running fine with an ammeter installed per the factory wiring diagram.

Check that the battery is in good condition. It’s easy to misdiagnose a charging system with a bad battery. Good time to replace it and start fresh.

Check the battery voltage with a multimeter (don't trust the gauge) while the engine is running and under a load. At the same time, check the system with a good quality ammeter. The ammeter is showing the actual charging system operation, while the voltmeter shows the end result (battery voltage).

Find out if operating the brake lights has the same affect as the headlights & turn signals. These are separate circuits. If the headlights really pull the system down, there might be a short to ground. Flipping on a light switch should show an immediate load with the ammeter, and almost instantly should show the alternator kicking in to charge the system. The ammeter is an excellent window into the operation of the charging system.

 

[Tom H]

Jan,

Yes, putting the ammeter in the charging circuit only, has a little less risk associated with it. But it also has almost no benefit either. If the alternator quits while traveling, the ammeter will show the normal reading of neither charge nor discharge, letting you think all is fine, even though all the operating current is coming from the battery. Then suddenly you find that you have a fully discharged battery with no warning at all. I don't think that's a good idea either. Since ammeter shunts have fewer failures than alternators I think wiring it the way the factory did is a better solution. The benefit outweighs the risks. In your scenario, If the shunt blows and the system stops charging it will only be a matter of time before the battery dies anyhow, and again, you'd have no warning that there was even a fault. If you are concerned about the risk of an ammeter shunt failure, I think you'd be better off to not use an ammeter at all.

Eric, Drnobeam also has a good idea. Get yourself a multimeter. You can get perfectly good Digital ones or analog (meter needle) types for $20-30. I cannot imagine how I would troubleshoot a problem like yours without one.

Tom H

 

[Nickodell]

Banging an old drum of mine (one of mine, anyhow); this is one more case where a clamp-on D.C. multimeter is an irreplaceable diagnostic tool. I've had one for some 20 years, and there is nothing, nothing else that will tell you as much in an hour of fiddling about as it will in ten seconds.

With the multimeter set at D.C. amps, I would first start the engine and clamp the sensors around the output wire from the alternator. With a healthy battery you should get a few (maybe 5) amps as the alt replaces the juice used to start the engine. Then switch on accessories one by one and the alt should respond by increasing its output in step. If it doesn't, you either have a bad alt or the wiring set-up is incorrect.

My D.C. multimeter cost some $500 in today's money (didn't cost me a dime, I expensed it) and I forgot to give it back to my employer when I retired.

Today they cost a third of that. You also get a high-quality digital DC voltmeter, AC ammeter and voltmeter, and ohm meter. You can also use them to detect current leakage (they measure down to hundreths of an amp) and reversed polarity among a host of other stuff.

Don't confuse a D.C. clamp-on with the stuff you see in Sears and Loews for $40; these are A.C. only.

 

[serIIalpine]

I have no ammeter or voltmeter installed in my car and I do use a multimeter and I take a reading from the poles of the battery.

Aside from this my instilation is as described in the tech note.

I'll try to figure it out tomorrow.

Thanks

Eric

'62 SerII

 

[Nickodell]

Eric; we're talking apples and oranges. Measuring voltage at the battery can be very misleading. E.g., a fully charged battery can give you 14v or so off load, but that tells you nothing about how much juice the alternator is putting out. It could be just enough to match the couple of amps the ignition circuit needs with the engine running, and maybe an amp or two into the battery, which would be enough to keep it charged until you turn power-grabbing stuff like lights and heater fan on, then it starts to drain.

 

[Drnobeam]

I like to use both a voltmeter and a (DC) ammeter when checking a charging system. A digital voltmeter shows if the battery is being over or under charged. An analog ammeter makes it easier to see the workings of the electrical (load side) and alternator (charging side) of the system. I find it easier to watch the needle on an analog ammeter vs. the constantly changing numbers on a digital meter.

You can also check DC amps (for a lot less money) with a multimeter set to the millivolts setting. You're actually checking voltage drop, but the reading is the same as DC amps. If anyone is interested in how to do this, let me know.

Operating different circuits like brakes, headlights, and turn signals independently, and watching how they effect the charging system (with the ammeter) as you increase engine rpm will give you an idea of how the charging system is reacting to the loads of the electrical system.

 

[Nickodell]

You can also check DC amps (for a lot less money) with a multimeter set to the millivolts setting. You're actually checking voltage drop, but the reading is the same as DC amps. If anyone is interested in how to do this, let me know.

I would like to know, especially how this method measures alternator output - which is the crucial point in question - in the way a clamp-on DC ammeter does?

 

[Tom H]

Nick,

It's a pretty simple concept. You just use the resistance of the wire as your shunt. I have not done it, but if you pick a couple points in the cable, measure the length between the points, knowing the guage of the wire you can come pretty close to the correct resistance of that length of wire. #10 wire is about 1 milliohm per foot. Then using the millivolts scale and ohms law you can convert to amps. If your "shunt" was a 1 ft section of the #10 wire (?) from the alternator, each millivolt will represent 1 Amp.

I think the ammeter on my 1973 Dodge van actually used a similar arrangement.

Keithley Instruments, my employer, actually makes a high end Digital Multimeter that has an "in circuit" current measurement function where the instrument first mearures the resistance between any two points on a circuit board and then measures the voltage drop across the two points and calculates and displays the current flowing through that path without breaking the circuit and without use of any magnetics .

Tom H