Alternator not working

[JMiller29]

Hi all.

The Delco alternator on my 1952 8N never worked well. It had to be revved up to get it to kick in.
I realize I didn't have the exciter wire with a bulb, but never got around to that.
Suddenly it stopped working at all. I put on an exciter wire and bulb, but that didn't help. I figured it was dead and ordered a new (Rebuilt) one.
It doesn't work either. I took both to an auto shop and both tested GOOD, yet they still insist on not working on my tractor even at maximum engine speed. The only possibility I can think of would be a bad ground so I attached a ground wire from the ground lug on the alternator to the battery. It still won't kick in. The battery measures 12.2 volts while running and the ammeter is at zero. I'm bumfuzzled. Any ideas?

 

[wore out]

You likely have an ''open'' in the wiring somewhere between where the battery cable and power wire attach to the starter solenoid and the output stud on the alternator.

Does it still have the OEM-style Ammeter?

If it has an Ammeter with two terminal studs on it, the Ammeter itself could have failed internally.

 

[Denny K]

If it had to be reved up to work, you need the small dia. pulley for it. 20 years ago I fought my 8n alt. until I figured it out.

 

[used red MN]

Well I have to ask, are these one wire alternators and you are pulling the plug out and connecting to the 1 and 2 terminal spade expecting them to work? Those spades go into the internal voltage regulator which the rebuilder may have sourced particularly for one wire configuration. This means they MAY NOT have the circuitry to support functions of external connections. If the alternators are not specifically one wire then as wore out suggests there is something wrong in your wiring or since you say it never worked properly then something in the wiring may be incorrect. Here is a diagram to compare to what you have, report back any differences yours has compared to the 2nd one in the link.
Ford wiring diagrams

 

[used red MN]

My apologies wore out, but to clarify an ammeter that
has a failure to cause in not to register a charge or
discharge could easily be diagnosed especially if your
tractor has lights. Turn on the lights if they work then
the ammeter should show a discharge, if it does the
meter will most likely be able to register a charge
value. Turning on the ignition if the points are closed
which they usually are with the engine stopped will
register a slight discharge of several amps. An
ammeter that has failed open and the tractor is wired
correctly would cut power to the ignition and lights, so
your tractor would not run at all.

 

[Eman85]

It sounds like you have a voltmeter, start tracing backwards in the circuit and see where you lose the voltage.

 

[JMiller29]

Thanks for all your ideas.
I'll get a chance to look at it again on Tuesday and will trace all the wires.
I'll let you know what I find.

 

[JMiller29]

Well, here's what I did:

I traced back all the wires to the connection block, ammeter and starter, cleaned all the connections and reassembled.
I put the new remanufactured alternator on and it still didn't work.
I put the old alternator on, and it DID work after revving it up, even with the exciter circuit installed. Am I correct to understand that the exciter circuit gets the alternator going at lower RPMs? It does appear to have a small pulley, by the way.

My diagnosis is that the new rebuilt alt is bad, and the old alt is sick. What do you think?
I guess I'll have to roll out the big bucks for a brand-new alt.
Is there a favorite unit for a '52 8N?

 

[HFJ]

(quoted from post at 14:08:44 03/07/23) Well, here's what I did:

I traced back all the wires to the connection block, ammeter and starter, cleaned all the connections and reassembled.
I put the new remanufactured alternator on and it still didn't work.
I put the old alternator on, and it DID work after revving it up, even with the exciter circuit installed. Am I correct to understand that the exciter circuit gets the alternator going at lower RPMs? It does appear to have a small pulley, by the way.

My diagnosis is that the new rebuilt alt is bad, and the old alt is sick. What do you think?
I guess I'll have to roll out the big bucks for a brand-new alt.
Is there a favorite unit for a '52 8N?

afaik, most conversions use a delco 10SI

 

[deanostoybox]

''The Delco alternator on my 1952 8N never worked well. It had to be revved up to get it to kick in.''

Most likely a ''one wire'' alternator with a ''self exciting'' regulator.

''I traced back all the wires to the connection block, ammeter and starter, cleaned all the connections and reassembled.
I put the new remanufactured alternator on and it still didn't work.
I put the old alternator on, and it DID work after revving it up, even with the exciter circuit installed. Am I correct to understand that the exciter circuit gets the alternator going at lower RPMs?''

Well, yes and no, mostly not. A self exciting regulator depends on residual magnetism and RPM to generate enough voltage to turn the regulator on. Supposedly there are some self exciting regulators that will accept excite current, I have not seen one yet. A three wire alternator will self excite if it turns fast enough IF the sense wire is connected to battery voltage. When the sense wire (terminal 2 on the pigtail connector) is connected to battery voltage the regulator is on. The output transistor in the regulator is biased on which grounds the brush connected to it and one end of the field winding inside the rotor via a slip ring. The other end of the field winding is connected via a slip ring and brush to the excite terminal (#1 wire in the pigtail connector) and to the output of the diode trio. When the excite terminal is supplied with current, that current flows through the field coil magnetizing the rotor so as soon as the rotor starts turning the alternator starts generating. In the case of an idiot light, when the output voltage reaches battery voltage the light goes out.

So with the key on, engine not running, you should have battery voltage at both the alternator output terminal and the sense terminal. There should be some voltage at the excite terminal as well (light is on). If those conditions are met, the alternator should start to have output at no more than 500 RPM (engine). At 350 RPM probably not enough to show a charge, but it will be generating.

'' It does appear to have a small pulley, by the way.''

Pulley should be about 2 1/2 to 2 3/4 OD in order to get about 2 to 1 increase from crankshaft speed.
Speaking of pulley, it needs to be a 5/8 wide pulley for a 5/8 belt. 1/2 inch belt will tend to slip on crank and water pump pulleys. I have seen a few home brew 12V conversions where the alternator pulley is the 1/2 that came on it, did not fit the belt so a 1/2 inch belt was used. it will work for a while until the inside of the belt and the bottom of the crank pulley become glazed, then trouble starts.

 

[Jim.ME]

Is the crankshaft pulley, the fan/water pump pulley, and the alternator pulley all the same width, so the belt fits properly in each one? A narrow pulley in the mix will cause the belt to wear narrow, can lead to bottoming out, and slipping in the wider pulleys. I ask as sometimes people leave the pulley that comes on an alternator on it and don't change it to a wider pulley if needed.

What is the diameter of the alternator pulley you have? There might be a smaller one available.

 

[Joe.S.AK]

29,

Unless you just like screwing around for hours on the tractor, out back in the barn, you might just want to consider pulling the alternator and taking it to one of the larger car parts stores (You Know the - "We test Alternators [color=green:f6fe0db756][b:f6fe0db756]FOR FREE[/b:f6fe0db756][/color:f6fe0db756] places.)

They're professionals at that sort of thing, with state of the art testers and highly trained folks. You'll end up with a fast, easy, and comprehensive analysis to find ANY problems that you have (or don't have) as well as "weak" areas that hit-n-miss spot testing could easily miss.

Your choice

 

[Jim.ME]

(quoted from post at 19:13:48 03/07/23) 29,

Unless you just like screwing around for hours on the tractor, out back in the barn, you might just want to consider pulling the alternator and taking it to one of the larger car parts stores (You Know the - "We test Alternators [color=green:2014794aaa][b:2014794aaa]FOR FREE[/b:2014794aaa][/color:2014794aaa] places.)

They're professionals at that sort of thing, with state of the art testers and highly trained folks. You'll end up with a fast, easy, and comprehensive analysis to find ANY problems that you have (or don't have) as well as "weak" areas that hit-n-miss spot testing could easily miss.

Your choice

In his first post he said he had them both tested at an auto shop and they both tested good.