Charging circuits / diagnosis

[apb]

Does anyone know of modern instruction for testing the charging circuits for generators / regulators?

All the procedures in the shop manual uses pretty old equipmement. I know I can reproduce some of it with modern instrumentation as a voltmeter today is better than it was then etc.

The mystery of the Allen tester etc is what are the switches connecting?

I would think that modern instruments would allow one to trouble shoot the system by measuring voltages and perhaps some resistance. I am pretty familiar with electronics and know for instance that I should be able to measure the resitance of a field coil and not have to connect 12V and measure the current. In this case the resistance can be calculated from the current specified at 12v.

As one may guess from all this ramble I have a generator system that is not charging.

[JohnD1956]

Presuming this is on the 55, I would think there really is not too much to test. The amp guage in the dash is going to give you a reading under the possible scenarios unless it was disconnected in the past. by this I mean it is live all the time. If there is a short causing a draw that's killing a battery, the guage would register a discharge when the car is off. If the car starts, and continues runing, I don't believe there is much left to test. If the amp guage is registering a discharge while the engine is running above an idle, the first thing to do is polarize the voltage regulator and check it again. If still discharging then the only thing to do is repair the generator. Note, at idle without the lights on you may see a slight discharge rate on the Amp guage. With the lights on you will definitely see a discharge.

I was surprised to find out that generator in this vintage will only put out 35 amps. A Generator from an A/C car will only do 55 Amp. So if there is a lot of electrical draw from newer things, like stereo's or other goodies, then you may need to develop a different shut down procedure, like turning off all optional electrical draw a few miles from home and giving the system a chance to replenish the battery.

[apb]

The car does show discharge when running, even at a pretty good clip (I don't have a suitable Tach). I am not familiar with polarizing the regulator so I will need to figure out what that's all about.

I haven't had this car on the road much so I'm not sure how bad the problem is yet. The charge seems to come up a bit when up to speed but doesn't get above horozontal. I don't think there is any discharge when off and there is no additional load added to the car.

I'm going to Cruzing Grand (the local Friday night thing) for the first time tonight so I shold know more tomorrow.

[Aaron65]

Do you have a starter shop in town??? If you pull your regulator and generator, they'll usually test them for free...you probably have a bad regulator. You can check the brushes on your generator...they're visible through the back...you may need a flashlight and small mirror. If your gauge doesn't go above horizontal, you aren't charging.

Here's a site I found on google about polarization...there are others.

http://www.texaspowerwagon.com/polarize.htm

[apb]

Aaron,

Thanks for the link. It looks like what you are doing is establishing the polarity of any iron in the system. I was not aware of that need.

I suspect that is OK on my system as it charges a little, just not enough.

The guess of the regulator is probably a pretty good one. I tried to pull the cover to check the contacts and it seems to be installed with rivets. I have a spare but it has a welded contact. I also have a spare generator of dubious functionality.

I'll just have to keep peeling the onion.

[Guest simplyconnected]

Some of the auto parts stores will NOT check generators, but they do check alternators. It seems their test stand doesn't do generators, and store guys don't know much about old technology.

Want to test for a good/bad generator? Here's a real 'down and dirty' method:

With the engine off, pull the generator FIELD and ARMATURE wires and tape them off (temporarily). Put them safely off to the side. Next, jumper the FIELD terminal to the ARMATURE terminal on your generator, then start your engine. Starting from an idle, put an electrical load on the 'test jumper'. (I like to use a known-good headlight because it draws a lot of watts.) Hook one headlight lead to ground, and the other to your 'test jumper'.

Be careful not to over-rev; give the engine a little gas. You should see the headlight brighten. Remember, there is no regulator, and too much RPM's will produce over-voltage which will burn out your light. (You can tell when the light is bright enough.) This test allows you to see the generator produce enough power to charge your system.

If the light never shines, the generator isn't making power and should be replaced.<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Aaron65</div><div class="ubbcode-body">...You can check the brushes on your generator...they're visible through the back...you may need a flashlight and small mirror</div></div> Carbon brushes only cost a few bucks. When they wear down to nubs, the spring tension goes away causing arcing and burning of the commutator segments (major damage). I agree, Aaron65, "an ounce of prevention"...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: apb</div><div class="ubbcode-body">...I have a spare but it has a welded contact.</div></div> Pull the contacts apart and use a 'points' file to smooth the surfaces. Just because it stuck once doesn't mean it can't be fixed.

[apb]

The point about brushes is good advice. I'll have to check the condition.

I tried to separate the contacts but they are well and truly stuck. I thought about heating with a soldering iron but suspect that one is gone.

[old-tank]

Archie

Maybe the battery is fully charged. If so the amp guage neddle will be horizontal. Turn on the headlites for a few minutes and then start the engine...it should show a charging condition until the battery is again charged.

Willie

[apb]

No, it really is discharging. I took it to Cruzing Grand last night and coming home it was a good thing I had a good freshly charged battery as the old needle was really drooping.

It does come up a little when the revs increase but not nearly enough to get to positive ground.

I'll try to look at the brushes today and perhaps drill the rivets and look at the regulator.

[Guest imported_JPIndusi]

First make sure the regulator case is grounded securely. Use a jumper with alligator clips if needed to assure good ground. If ammeter shows charge with engine revving above idle you are done. If not connect a jumper from the field terminal to ground of the regulator. Start engine and rev to a speed above idle but not too fast. If it charges now, the regulator is at fault. If not, repair the generator.

Good luck.

Joe, BCA 33493

[apb]

That's pretty straight forward. Is it really that simple?

[Guest imported_JPIndusi]

It certainly is. I s__t you not! I assume this is a 1940-60 Buick. Look at the charging circuit wiring diagram and you will see that by grounding the field terminal you apply the full voltage across the generator field coils essentially bypassing the voltage regulator. If it shows a charge on the ammeter with field terminal grounded then the generator is likely OK but the regulator needs replacing. If it doesn't show a charge condition then it is likely the generator that needs work. Just rev the engine to the equivalent of about 20-25 MPH, no faster.

Good luck.

Joe, BCA 33493