The Stovebolt Site Forums The Shop Area The Electrical Bay 1959 36 235. Alternator vs. Generator

Well it looks like the generator on my 1959 Apache 36 with the 235 has finally stopped charging the battery and needs to be replaced. I don't know if there is a common upgrade for these generators or not. So, I'm not sure whether to:
a) have the current one rebuilt
b) replace with a new or reman generator
c) replace with a new or reman alternator
Any help would be appreciated.

May not be anything more than worn brushes. A good generator shop should be able to fix it reasonably if you want to keep the truck stock.

Other wise it's easy enough to swap over to an alternator.

Hidiy apache3600-

Here's a detailed Tech Tip that explains the functional differences in generators and alternators, if you are interested.

Your "a" and your "b" option is basically the same, but paying a shop for a complete rebuild of the generator(a) you have will probably save you $40-$50 over purchasing a remanufactured generator(b).

Brad

Thanks for the information Roy and Claude. I'm starting with a fresh battery at 12.6 volts. How do you test to see if its the generator or the voltage regulator that is bad? I only drive the truck about once a week and keep the battery disconnected in between drives, but the truck does go through batteries, about one year.

http://www.stovebolt.com/techtips/electrical/electrical.html

Scroll down a little on the page and you'll find the tech tip on how to diagnose what is wrong.

Which one of the two terminals is the field terminal?

On the regulator it should be marked. May be with "F" or "FLD"

Mounted on the truck the top connection is "Bat" the middle is "ARM" and the bottom connection is "FLD"

Kinda hard to see the writing on the terminals.

Here is a link to one on Ebay and you can zoom in on the pictures to see which terminal is which.

http://www.ebay.com/itm/Voltage-Reg...ries&hash=item5b043a9536&vxp=mtr

I did both tests in the article. With wire hooked up to field on regulator and grounded to engine on the other end, I increased rpm. The amp gauge didn't move. So according to the article, this is a sign of a bad generator. The second test, where I leave the wire attached to the field terminal of the regulator and strike the other end of the wire against the block, does produce a spark, although a weak one. According to the article, no spark means the generator isn't working. Does that mean that since I got a spark the generator is working? Based on the two tests it seems I got conflicting answers.
I have the idle set at around 475 rpm which is what the manual says. At idle what kind of voltage should I be getting at the generator and also at the battery. With all accessories on, what should be the voltage at generator and battery?
Lastly, the amp gauge didn't move on any tests or when I turned on all the accessories. The needle just stayed right in the middle.

May need a volt meter to measure what's happening at the battery. The amp gauge should show a slight discharge while the engine is running if the generator is not working. And should show a slight charge above idle if it is.

Not moving either way may mean some one has by passed it or it is stuck.

Put a volt meter on the battery and see what voltage is shows when you rev the engine just above idle.

I'll do that and let you know. When replacing a battery or simply removing a battery cable from a battery terminal and then putting it back on, do you need to polarize you generator every time or never?

polarizing only advised when replacing a generator or regulator, disconnecting the battery won't affect anything ... unless you hook it up backwards [+ ground]

Bill

The main reason they stop charging is usually the brushes. All you have to do is look into the end of the generator to see the condition of them. Replacing them is pretty simple also. Also if your batteries are only lasting a year you may have an overcharging issue. That would most likely be a regulator issue.

There is another quick test you can do. Remove, or at least loosen the fan belt until you can easily turn the pulley by hand. Apply battery voltage to the Armature terminal of the generator with a fairly heavy jumper lead, 12-14 gauge or so, and give the pulley a little spin by hand. A good-condition generator should "motor" (spin as long as voltage is applied to it). If it will motor, it will also generate.

A voltmeter connected between the Armature terminal of a polarized generator and the engine block with the belt tight and the engine running should show at least 1/2 volt even with the wires disconnected. When the Field terminal is grounded with a jumper lead, the voltage should rise without limit as the speed is increased. If the generator passes these tests the problem is in the regulator or the connecting wiring.
Jerry

As apache 3600 has said, the amp meter is NOT moving when lights ect. are turned on,( Check that the amp meter is hooked up) so there is a open circuit somewhere. The first test to do is turn on the ignition and lights, motor not running, have someone watch the amp gauge while you wiggles all the wires from the generator to the regulator and then under the dash to see if the amp meter moves to discharge. If it does move at one point that will be the problem area. PS to Hotrod, if a amp meter goes open circuit does the battery stop charging, and if so can the amp meter wires be jumped together and then check the voltage at the battery to see if it is charging at the battery with the motor running.

Yes, it's unusual, but I have seen a few ammeters open circuit. If it's wired correctly, everything shuts down: ignition, headlights, charging system and all. That's because the "discharge" side of the ammeter also serves as the connection point for virtually all the circuits on the truck. If the upstream (battery) side of the ammeter has the load circuits connected to it, it will never show a discharge.
Jerry

It will also never show a charge if the amp gauge goes open circuit.

Since his gauge isn't moving one way or the other I think it is either by passed to take it out of the loop, or stuck. The only real way to know what is going on is to use a volt meter and see if the truck is charging or not.

And look closer at the amp gauge to see why it doesn't move.

This is what I found out:
Battery voltage at idle: 12.37
Battery voltage above idle: 12.57
Neg. battery terminal to voltage regulator batt: 12.36-12.5

Generator F to Voltage regulator batt: 12.56
Generator A to Voltage regulator batt: 12.56

Generator F to ground: 0.2
Generator A to ground: 0.2

Generator F to Voltage regulator F: 0.2
Generator A to Voltage regulator F: 0.2

It seems the generator is only producing 0.2 volts. Any opinions other than it being a bad generator?

What happened when you did the "motor" test like I suggested- - - - -I'll bet a shiny new dime you didn't bother.
Jerry

I once saw plans in a do-it-yourself book that used a car generator as a motor, wired as Jerry suggests, to power a homemade go-cart. It will pull 5 amps. My point is, don't be afraid to do this test.
Carl

I've used that test a few times. At the parts store one time a man brought in a generator from an old tractor and wanted to know if we could test it.

The other guys looked at it and said we couldn't. I looked over and said they could too.

Took them back and showed them how to check and see if it would motor.

I spun up pretty well best I remember.

Hotrod, I didn't do your test because I didn't see this second page of responses by you guys till now. I thought no one had responded to my question about polarizing because I didn't notice the responses to it were on page 2!
Well, now I'm on the same page, literally, and will do your test. Is it possible I'll get the generator to spin with voltage applied to it, but that it won't produce enough voltage because the brushes are worn or some other internal problem?
I'll check the ammeter too.
Thanks for your responses.

I'd suggest a thorough check of the physical condition of the generator first. Remove it from the vehicle, tear it down, and inspect the armature and field coils for damage or wear, install new brushes, clean up the commutator with a strip of non-metallic sandpaper, and be sure all the connections are clean and tight. Then do the motor test on the workbench, positive polarity to the armature terminal and negative to the generator housing. The armature should spin at a pretty good rate of speed if everything is in good shape. All it will cost you is a few bucks for brushes and a little labor time.

Polarize the generator after you reinstall it and check for voltage at the armature terminal with the field terminal grounded with a jumper wire. You should see a quick rise in voltage as the speed is increased above idle.
Jerry

1. Hotrod, I did your test, battery voltage to armature post on generator. The generator pulley spun great.
2. After putting the belt back on, I tried your other test, a voltmeter between the armature post on the generator and the block. When I tried this test a couple weeks ago, I got 0.2 volts. You said it should be at least 0.5 volts. Well, I got 14.5 volts today? I double checked everything was hooked up correctly. The only change I can think of is maybe the belt is now tighter since I took it off and put it back on.
3. Your third test, with the field terminal on the generator grounded to the block by a jumper lead, showed voltage climb to about 18.5 volts when I increased rpm before I stopped.
4. 12.5 battery voltage at start of tests, engine off.
13.2 battery voltage at idle.
14.0 battery voltage with increased rpm.
12.4 battery voltage at idle with fan, lights, high beams, and wipers on.
13.2 battery voltage with increased rpm with fan, lights, high beams, and wipers on.

Are those numbers within spec?

You nailed it! Those numbers will keep your battery charged without overcharging it. A fully-charged battery will need about 13.5-14.5 volts to keep it charged. If you want to really monitor the performance of the charging system get a hydrometer, the glass vial type with a float inside, and monitor the concentration of the battery acid. It should be somewhere in the range of 1.250-1.265 for all the cells, with a variation of no more than 10 points (.010) between cells. A completely discharged cell would have a specific gravity of 1.000 (plain water) and a fully-charged cell will be around 1.260, plus or minus a little which is the strength of the acid when the battery was new. A noticeable difference from one cell to another indicates the reactive material on the battery plates is sloughing off and accumulating at the bottom of the cell where it cannot enter into the charge/discharge reaction on the low-gravity cells.
Jerry

Jerry,
1. What about the battery voltage at 12.4 at idle with all accessories running? Is that too low?
2. What about the 14.5 volts I got when I put the voltmeter between the armature post on the generator and the block for ground. Didn't you say it should be about 0.5?
James

The 0.5V reading was supposed to be WITH ALL WIRES DISCONNECTED FROM THE GENERATOR! That's the way we check to see if the polarization worked.

Once everything is reconnected and the regulator is working properly, there will be about 1/4 volt drop from the armature terminal of the generator to the ARM terminal of the regulator, and another .1 or .2 volts drop through the regulator. It's not uncommon to find 1/2 volt or slightly more lost getting through the charging system to the battery terminals. Generators are lousy about developing voltage at idle speed, so being just above battery voltage at idle with a load on the system is normal. As long as the voltage comes up at a fast idle or above, the battery will stay charged. Putting a smaller pulley on the generator would make it charge better at idle, but then there would be a danger of throwing the windings out of the armature at cruise speed.

Any charging system, alternator or generator, supplies the accessories like ignition, lights, fan motors, etc. first, and uses whatever current is left over to recharge the battery. Turning all the accessories on simulates a heavy load on the battery and determines if the current regulator is set properly. Very few shadetree mechanics have sophisticated enough equipment to do a proper load test on a battery or a complete charging system. My charging system test equipment cost around $1,000.00, and it's not "state of the art" by any means- - - -just adequate.
Jerry

I'm gonna keep an eye on things for the next couple weeks and see if there are any changes. I'll take a look at that amp gauge too. So just to confirm, I have 12.5 volts at battery before starting and I have 12.4 at battery at idle with all accessories on. This is OK provided the voltage comes up at fast idle or above. Correct?
And is 13.2 volts at battery ok with all accessories on and above idle?
James

Yes, those numbers are OK. That's just telling you that running all the accessories at once is eating up most of the generator output and leaving very little for battery charging. 13.2 volts will maintain the battery's state of charge OK, it just takes a little longer to top it off with extra load operation. The generator is like a water pump filling a tank- - - - -if there are 5 or 6 leaks in the pipe before the water gets to the tank, it's going to fill a lot slower than if you use a pipe without a bunch of holes bleeding off some of the volume.

Electrical systems aren't really all that difficult to understand, but people just refuse to spend enough time learning the basics because we can't see the electrons go about their business!
Jerry