[robz]

Hi Guys.

I want to verify my charging system (no problem, just want to check it out as a preventive measure) and have searched thru archives to get most of the details on what to check. I have also my Chilton's and Petersen's manuals and keep seeing in their diagnosis that you need some sort of carbon pile to do various testing. What is that and do I really need one?? Also in my older multimeter (Dixco) it shows a shunt to use on alternator lugs..Is that acting as a jumper wire?

From the other posts I saw the following techniques for testing:

1) Voltmeter between battery posts while engine running, should show 13-14 volts if
charging system is OK
2) If it isn't, then remove plug off alt and jumper F term to Bat +ve and test with
voltmeter on Battery. Should jump to 16v, if alt and wire from alt to battery is
good.
3) To test alternator, not sure where to put voltmeter probes for alt output.
4 What tests are necessary for regulator.

I'd appreciate any answers you may have on the first paragraph as well as confirming my steps 1 and 2 and if you can, show me steps 3 and 4.

Thanx for your help.

Robert

[george kujanski]

First, a carbon pile is a high power, adjustable resistor.

To check your system, your multimeter should be all you need, unless you want to check if the alt can put out it's max rating.

Attach the meter to your battery, start the car, and note the battery voltage at idle. It should be around 14.0 volts

Turn on some loads, i.e. headlights, heater, A/C, one at a time and watch the batt voltage. If the batt voltage starts to droop, increase the idle speed slightly and it should go back to about 14.

With as many heavy electrical loads as you can turn on, i.e. headlights, stop l;ights, heater fan, A/C, etc. the voltage should be near 14 at increased engine speed, about 2000.

What the above tests show is that if the voltage is at about 14, the system is normal. When the voltage drops, it indicates the alternator can't keep up with the loads and the battery is not charging. This also may be normal at engine idle, but the voltage should go back to 14 as engine speed is increased.

Normally an alternator is sized such that with maximum loads on in the car, the battery voltage will be near 14 at typical cruising speeds.

Low-optioned cars usually got 37A (max rated @5000 shaft RPM) whereas cars with A/C, etc. would get 62A alts because of the higher electrical loads.

A carbon pile comes in handy for for testing max alt output because you can adjust the load manually rather than rely on the accessories in your car, but if the above tests are normal, your alt and reg are ok.

Make sure the belt doesn't slip at high loads also.

George

[robz]

Originally Posted by george kujanski

First, a carbon pile is a high power, adjustable resistor.

To check your system, your multimeter should be all you need, unless you want to check if the alt can put out it's max rating.

Attach the meter to your battery, start the car, and note the battery voltage at idle. It should be around 14.0 volts

Turn on some loads, i.e. headlights, heater, A/C, one at a time and watch the batt voltage. If the batt voltage starts to droop, increase the idle speed slightly and it should go back to about 14.

With as many heavy electrical loads as you can turn on, i.e. headlights, stop l;ights, heater fan, A/C, etc. the voltage should be near 14 at increased engine speed, about 2000.

What the above tests show is that if the voltage is at about 14, the system is normal. When the voltage drops, it indicates the alternator can't keep up with the loads and the battery is not charging. This also may be normal at engine idle, but the voltage should go back to 14 as engine speed is increased.

Normally an alternator is sized such that with maximum loads on in the car, the battery voltage will be near 14 at typical cruising speeds.

Low-optioned cars usually got 37A (max rated @5000 shaft RPM) whereas cars with A/C, etc. would get 62A alts because of the higher electrical loads.

A carbon pile comes in handy for for testing max alt output because you can adjust the load manually rather than rely on the accessories in your car, but if the above tests are normal, your alt and reg are ok.

Make sure the belt doesn't slip at high loads also.

George

Thanx for clarifying what a carbon pile is, George..and that I don't need one...

Can you let me know if the other tests I mentioned are correct, #1 and #2 (Pretty sure I got them from some of your responses on other posts, but wanted to have them all here to have a complete diagnosis pattern in one post) and what I have to do to test regulator and alt, #3 and #4?

Thanx again...

Robert

[george kujanski]

1 and 2 are correct; 2 just bypasses the regulator to see if the alt will go to higher voltage with full field.

3. If you are checking alt output voltage connect the probes from alt output to ground. You can also use the multimeter current function (DC amps) to measure alt output current, but most multimeters max out at about 20 or 30 amps, and the alt output is greater than that.

The shunt you mention is a precision low valued resistor that gets connected in SERIES with the alt output. It's used to measure large current values without using a high current meter. The current going thru it creates a voltage drop on it that can be measured with a multimeter using the low voltage function. They are usually calibrated such as 10milli-volts per amp so if, say, 60 amps is going thru it, 600 milli-volts will be measured by the multimeter.

By doing the above tests the regulator is being tested; i.e. it's job is to hold the battery voltage constant at about 14 volts. The reg failure modes are either stuck open, so the voltage is too low, contacts stuck closed so the voltage is way too high, or misadjusted, where the voltage is constant, but slightly lower or higher than 14, but not as high as, say 16, which is more of a stuck contact situation.

george

[robz]

Originally Posted by george kujanski

1 and 2 are correct; 2 just bypasses the regulator to see if the alt will go to higher voltage with full field.

3. If you are checking alt output voltage connect the probes from alt output to ground. You can also use the multimeter current function (DC amps) to measure alt output current, but most multimeters max out at about 20 or 30 amps, and the alt output is greater than that.

The shunt you mention is a precision low valued resistor that gets connected in SERIES with the alt output. It's used to measure large current values without using a high current meter. The current going thru it creates a voltage drop on it that can be measured with a multimeter using the low voltage function. They are usually calibrated such as 10milli-volts per amp so if, say, 60 amps is going thru it, 600 milli-volts will be measured by the multimeter.

By doing the above tests the regulator is being tested; i.e. it's job is to hold the battery voltage constant at about 14 volts. The reg failure modes are either stuck open, so the voltage is too low, contacts stuck closed so the voltage is way too high, or misadjusted, where the voltage is constant, but slightly lower or higher than 14, but not as high as, say 16, which is more of a stuck contact situation.

george

Thanx for the explanation and confirmation..So the regulator test is the one with Shunt explained above (Alt output being R?)?

Also you had mentioned in another post testing #2 term on Regulator, while engine running, for A/C volts (8V)...What does it do?

Also noted that 3 is the sense terminal on Regulator to see if battery needs more charging, and normally should be same as Battery voltage from +ve to -ve. So what exactly does F do?

Appreciate all your insight, George...

[george kujanski]

The regulator test is all of the above; the reg's job is to maintain constant battery voltage.

The alt terminal R means relay, and it's connected to the reg term 2.

The shunt is just a tool for attaching to the alt output to be able to measure high current without a specialized meter.

Terminal 2 on the regulator does the following: once the engine starts, terminal 2 gets about 8 volts AC from the stator inside the alt (term R); this voltage activates a relay inside the regulator to: turn off the idiot lite, and connect terminal 3 (battery) to the other relay inside the reg as the volatge sense point. IF the second relay was connected all the time, the battery would drain with the key off, that's why terminal 2 is used, only to connect the batt to the reg once the alt is energized.

Terminal F is the connection from the reg to the alt field. That's how the reg controls alt output voltage. If the reg senses batt voltage too low, it increases the field current to make the magnetic field in the alt stronger, and the alt output voltage goes up.

Conversely, say you turn off your headlights. With the headlights on, the field was stonger to allow more alt output. Once the headlights are turned off, momentarily the batt voltage goes up, the reg senses that and backs off on the field drive so the alt voltage goes back down.

In practice, the reg switches the field voltage (and the field current) up and down several times a second so the AVERAGE field drive produces the proper batt voltage.

George

[robz]

Originally Posted by george kujanski

The regulator test is all of the above; the reg's job is to maintain constant battery voltage.

The alt terminal R means relay, and it's connected to the reg term 2.

The shunt is just a tool for attaching to the alt output to be able to measure high current without a specialized meter.

Terminal 2 on the regulator does the following: once the engine starts, terminal 2 gets about 8 volts AC from the stator inside the alt (term R); this voltage activates a relay inside the regulator to: turn off the idiot lite, and connect terminal 3 (battery) to the other relay inside the reg as the volatge sense point. IF the second relay was connected all the time, the battery would drain with the key off, that's why terminal 2 is used, only to connect the batt to the reg once the alt is energized.

Terminal F is the connection from the reg to the alt field. That's how the reg controls alt output voltage. If the reg senses batt voltage too low, it increases the field current to make the magnetic field in the alt stronger, and the alt output voltage goes up.

Conversely, say you turn off your headlights. With the headlights on, the field was stonger to allow more alt output. Once the headlights are turned off, momentarily the batt voltage goes up, the reg senses that and backs off on the field drive so the alt voltage goes back down.

In practice, the reg switches the field voltage (and the field current) up and down several times a second so the AVERAGE field drive produces the proper batt voltage.

George

Excellent..That about sums it all up for me...I'll try testing soon and report back results (if anything abnormal)..Thanx again..

Robert