System not charging... how to test?

[Guest Tishabet]

Hi guys,

Everything seemed to be squared away on my engine... the timing is working great, the carb hesitation is gone, valves sound great, I'm holding a steady 20" of vacuum, etc.

Last night, however, I discovered that one very key part of the engine system is not working... I am not charging my battery!

I understand in laymen terms the roles of the generator (and how it differs from an alternator) as well as the voltage regulator, and it seems clear that one or both of these components is not doing its job. I'm not sure how to test them, however.

I own a multimeter... would it be safe to assume that I should be getting voltage from the generator where the two wires attach at the top? Approximately how much voltage and amperage should I be seeing at idle? What about when I rev up the motor?

I understand what the voltage regulator does, bot not really how it does it. When I check out my manual, they show the testing of the voltage regulator using a device with about three times as many leads as my lowly multimeter. Any advice on testing functionality?

Any help troubleshooting the system would be extremely helpful! Thanks in advance.

[jeff]

OK - lots of possibilities here. I'll just try to scratch the surface, maybe it will get you started. First, check the integrity of your wiring and connections. Also, I am assuming your battery is OK, you should be able to charge it from your shop battery charger without drawing excess current - and it should have reasonable capacity to crank your engine a number of times before needing a new charge. If so, you can be reasonably confident in your battery - of course the only real test is a "load test" at your local battery shop.

There is a cover over the brushes and commutator of your generator. Take this off and take a look. The comm should be reasonably clean and shiney - I think you can do an "on-car" cleaning with the end of a pencil and a piece of very fine emery cloth (the black stuff, not sand paper). Tape the emery cloth to the eraser end of a pencil and touch it to the comm while the engine is running (wearing safety glasses). Let me know how this works, as I have always done a disassembly to clean the comm. Disassembly allows you to gently (very gently) clean the grooves between the comm bars as well. If all is well you should see 5 - 7+ volts at the generator terminal, depending on engine speed.

Now, the regulator. You have two relays in the regulator. One is called the cut-out relay - it opens when generator voltage is below battery voltage (low engine speed) and closes when generator voltage rises above battery voltage. This is to keep the battery from feeding the generator. Take a really fine piece of emery cloth and clean these contacts.

The other relay is the voltage regulator itself. Its contacts vibrate open and closed to open / close the field circuit of the generator. In this way, the voltage is "regulated" to about 7.5 V at most speeds above idle. Now, all of the extra functions of the test rig you are reading about are basically to establish a known load on the system to evaluate the regulator performance. If you recognize the uncertainty with just using your voltmeter, you can read directly across the battery terminals to evaluate the regulator performance. You should see just battery voltage at idle, then increasing voltage as you increase the engine speed. The voltage should go to about 7.5V, then hold there as engine speed continues to increase. (Again, without a known load, you can't be sure about the 7.5 V. But you can observe the general trend.) Clean these contacts as well.

That's about it - If the generator doesn't have an internal short or open circuit, and the relay coils are OK in the regulator, and there are no hidden shorts or opens in the harness, you should be all set. Hmmm, that's a lot of "ifs"!

Jeff

[Guest Tishabet]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">OK - lots of possibilities here. I'll just try to scratch the surface, maybe it will get you started. First, check the integrity of your wiring and connections. Also, I am assuming your battery is OK, you should be able to charge it from your shop battery charger without drawing excess current - and it should have reasonable capacity to crank your engine a number of times before needing a new charge. If so, you can be reasonably confident in your battery - of course the only real test is a "load test" at your local battery shop.</div></div>

Yes, battery takes charge well from my shop charger and the wiring is good.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">There is a cover over the brushes and commutator of your generator. Take this off and take a look. The comm should be reasonably clean and shiney - I think you can do an "on-car" cleaning with the end of a pencil and a piece of very fine emery cloth (the black stuff, not sand paper). Tape the emery cloth to the eraser end of a pencil and touch it to the comm while the engine is running (wearing safety glasses). Let me know how this works, as I have always done a disassembly to clean the comm. Disassembly allows you to gently (very gently) clean the grooves between the comm bars as well. If all is well you should see 5 - 7+ volts at the generator terminal, depending on engine speed.</div></div>

I have examined the commutator, it looks nice and shiny and the wiring all looks clean and good. I will try the pencil cleaning as well... being careful about the graphite end, of course!

I will use the multimeter to measure voltage at the generator and report my findings.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Now, the regulator. You have two relays in the regulator. One is called the cut-out relay - it opens when generator voltage is below battery voltage (low engine speed) and closes when generator voltage rises above battery voltage. This is to keep the battery from feeding the generator. Take a really fine piece of emery cloth and clean these contacts.</div></div>

Will do. Are these contacts "points" like in the horn or distributor?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The other relay is the voltage regulator itself. Its contacts vibrate open and closed to open / close the field circuit of the generator. In this way, the voltage is "regulated" to about 7.5 V at most speeds above idle. Now, all of the extra functions of the test rig you are reading about are basically to establish a known load on the system to evaluate the regulator performance. If you recognize the uncertainty with just using your voltmeter, you can read directly across the battery terminals to evaluate the regulator performance. You should see just battery voltage at idle, then increasing voltage as you increase the engine speed. The voltage should go to about 7.5V, then hold there as engine speed continues to increase. (Again, without a known load, you can't be sure about the 7.5 V. But you can observe the general trend.) Clean these contacts as well.</div></div>

When you say "directly across the battery terminals" do you mean the terminal marked "batt" on the voltage regulator itself? I assume testing across the actual battery posts will fry my multimeter, correct?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">That's about it - If the generator doesn't have an internal short or open circuit, and the relay coils are OK in the regulator, and there are no hidden shorts or opens in the harness, you should be all set. Hmmm, that's a lot of "ifs"!

Jeff </div></div>

Thanks Jeff!

[jeff]

Your commutator sounds OK - sometimes they are gummed up and blackened from excess oil at the front bearing. Forgot to mention, you should see brushes with some life left.

The contact points look a lot like distributor points.

Measure at the generator from the generator terminal to ground. Measuring across the battery terminals is just fine - just be sure you are in the voltage mode of your multimeter. The meter's high impedance will ensure that very minimal current flows through the meter.

Jeff

[Guest Tishabet]

Sounds good, I will let you know what I find out.

Thanks again for your help Jeff!

[Gene Brink]

Grant,

Any chance you replaced your voltage regulator? If so you need to polarize it (procedure should be in your shop manual). If you had the car apart for a long time you may need to do the same to the original regulator as well.

Good luck.

[Guest Tishabet]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Grant,

Any chance you replaced your voltage regulator? If so you need to polarize it (procedure should be in your shop manual). If you had the car apart for a long time you may need to do the same to the original regulator as well.

Good luck. </div></div>

<img src="http://forums.aaca.org/images/graemlins/shocked.gif" alt="" /> No, I never polarized the regulator! I got the generator and regulator in a cardboard box along witht the car, and have since replaced both the battery and the entire wiring harness. Clearly I need to do this first, and see if that takes care of the problem.

I just read through all that I could find about polarizing the system, and it sounds like I might have damaged the system by running the engine without correctly polarizing it. If I have damaged it, which parts would I have damaged?

[Buicksplus]

It does not hurt your generator or regulator if it is not correctly polarized. All that happens is the cutout in the regulator will not close and the generator never gets connected to the electrical system. So there is no charging but I don't believe there will be any damage.

The way I polarize a generator is to disconnect the output lead from the generator (the "A" terminal), leave the smaller field terminal in place. Then take a jumper wire from the ungrounded lead of your battery (the positive lead if your Buick is negative ground) and touch it momentarily to that A terminal. You should get a small arc when you do this and the generator will actually attempt to turn as a motor.

This should leave the generator properly polarized for your car. Reconnect the output lead and the system should generate OK -- providing that improper polarization was the problem initially.

If that isn't it, you need to check the regulator and components inside the generator. I usually take the generator off and test it on my bench. Just ground the field terminal and spin the generator by hand. The "A" terminal should generate a volt or two just by spinning it by hand. The voltage should be positive if your car has a negative ground. If it is the wrong polarity, polarize the generator until it generates the polarity you need.

Another simple test is to connect the generator to a battery, or better yet a small 6V charger (use the same polarity as the car). With the field grounded, it should turn as a motor. If your generator does this, it is probably OK.

Bill.

[Guest Tishabet]

OK guys, I went to the garage last night.

First thing I did was polarize the system by using a jumper to attach the battery and generator terminals on the voltage generator. I used some 14 gauge wire and touched it briefly 3-4 times, causing a healthy spark.

Next, I started the engine and broke out my trusty multimeter. I tested the voltage from the "A" terminal and "F" terminal on the generator with the engine at idle... .6 to .7 volts. <img src="http://forums.aaca.org/images/graemlins/frown.gif" alt="" />

When I reved up the engine, the voltage went up as well... at times as high as 1.4 volts <img src="http://forums.aaca.org/images/graemlins/mad.gif" alt="" />

At just about that time, the car ran out of gas... I guess that 2.5 gallons I put in the tank before the engine ran fo the first time could only last so long.

For what it's worth, I also checked continuity and discovered that i have continuity from the F post to the A post... that doesn't seem right if I'm trying to create voltage across the posts... <img src="http://forums.aaca.org/images/graemlins/confused.gif" alt="" />

I'll be going back (with more gas) tonight. What should I be doing/testing next?

[jeff]

I think you want to check from "A" to ground.

Jeff

[Guest Tishabet]

Got it! Terminal A to ground.

What about the continuity between A and F? Does that make sense?

[Guest imported_JPIndusi]

Continuity between A and F is because of generator internal connections.

This is not useful for troubleshooting.

With engine running at a little above idle, check voltage at A to ground. If below 6 volts, jumper F to ground. If voltage now increases to about 7 volts or more, regulator is defective. If still no increase in voltage, trouble may be in the generator, regulator or wiring. This assumes a good battery and tight and clean connnectios.

[Guest Tishabet]

Last night I headed over with a better multimeter, and now I'm seeing zero coming out of the geneator (measured from A to ground at the frame or engine block) no matter what RPM.

The internals of the generator were clearly replaced by the PO; the brushes appear new and their copper wiring is bright and shiny.

What could be causing the generator to put out zero? Is something grounding inside the generator? Should I start disassembling and see what I can see?

Thanks for the help guys!

[Buicksplus]

Start by disconnecting the A and F terminals on the generator to take the regulator out of the circuit for testing. Then get a jumper and connect the F terminal to a good ground. This will set up the generator for maximum output (the regulator should do this, but it may not be working right.) Start the engine and at idle measure the voltage on the unconnected A terminal. Do not rev up the engine or run it for long, it is possible to damage a generator by running it open circuit like this. You should measure significant voltage on the open A terminal, close to 6V at the proper polarity at idle. If you still get nothing, the problem is inside your generator. I would recommend removing the generator at this point for bench testing it or taking it to a shop, it probably has an open field or armature. Since it has been rebuilt, improperly grounded brushes or miswired internals could be the problem.

If you get voltage at the A terminal, then stop the engine and measure the resistance between the F wire (not the terminal, the disconnected wire) and ground. It should be zero. If not, your regulator is either not working, not grounded, or not wired properly. Check to make sure the regulator frame is actually grounded (be aware of new paint on the cowl, an ungrounded regulator will not work at all!). I have found that Delco regulators rarely fail completely, they usually are miswired or not grounded. Hopefully this will be your problem.

If the regulator looks OK, take the generator to the bench and measure the resistance between F and ground and A and ground. You should get a low resistance here. If not, make sure the brush plate on the back of the unit is properly grounded. You can next measure the resistance of the field and armature separately, but you will need to remove the end plate and disconnect the brush assembly from the field to do this. If you have a generator repair place in town, it might be best to give them the generator for testing. It's not rocket science, but getting the brush plate off and back on without damaging the brushes or wiring is tricky.

[Guest Tishabet]

Will do! I'll let you guys know what i figure out and whether I end up just taking it to a shop.

Thanks again!

[Guest Tishabet]

Hey guys,

an update for you:

With my newfound knowledge of generators (thanks to you guys!) I tested my generator again... only putting out about 1/2 volt. <img src="http://forums.aaca.org/images/graemlins/mad.gif" alt="" />

So, I bit the bullet and stripped the whole thing down, replaced some suspect wiiring, cleaned my commutator with the emery cloth, replaced the almost new brushes, and put it all back together again.

After polarizing the generator, I got a healty 6.7 volts at 10mph! For the first time ever, my ammeter was reading in the positive. I tested the regulator as well, and it's switching properly and charging my battery.

Thanks so much for all of the knowledge and help, guys. I am feeling far more confident both in my generator and my ability to service/diagnose it in the future. <img src="http://forums.aaca.org/images/graemlins/smile.gif" alt="" />

[Gene Brink]

Congratulations, Grant. And now on to the wedding... <img src="http://forums.aaca.org/images/graemlins/smile.gif" alt="" />