alternator not up to the task

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newguy

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The alternator is over eight years old, but only has about a thousand miles on it, battery is good. The car while running only puts out 12.5v at the battery, and while cruising around and coming up to longer lights, the gauge goes pretty low, and swings with the ticking of the turn signal.

The car has not stalled due to this problem, and when cruising at speed is at have way or higher on the gauge, but plan on going to car craft in a couple of weeks, and driving through there is a SLOW progress and don't want a problem to crop up.

Any ideas where to start?

thanks as always :)
 
Well you have two choices:

1 Throw parts and money at the problem, and THEN make some tests

2 Make some tests and determine the problem first

Might be a bad alternator, and might just be bad brushes

Might be a bad regulator

Might be a wiring problem

Might be a bad battery

Might be a combination of most/ all of the above

FIRST Charge the battery, find someone with a legitimate carbon pile load tester like this:

and have them load test the battery. If you can open the battery (old school with real caps) find a hydrometer and check specific gravity of the cells

load tester, 'xample:

auto3.jpg


hydrometer. Get one with a thermometer:

pACE3-997934reg.jpg


NEXT Some simple tests you can do

1 With engine running at fast idle to simulate low/ medium cruise, use an accurate meter to measure battery voltage right at the battery. When the engine/ battery/ regulator are warm, you should not have less than 13.5, not more than 14.5. 13.8---14.2 is optimum

2 If not, find the green and blue "push on" terminals on the alternator field terminals. Unhook the green, and install a clip lead from that alternator field terminal to ground. Again with the car running, watch the ammeter/ voltmeter and gently bring up the RPM. This SHOULD put the alternator in a "full field" IE "full output" condition, so if the wiring is OK and the alternator is OK, it should "bury" the ammeter at "C" at some RPM, and start raising the battery voltage. Don't allow it to go over 16V or so

3 If not, move your meter from the battery over to the alternator output stud and see what the voltage is there. If it's more than a volt or two higher at the alternator output than at the battery, you have a wiring/ connection problem in the bulkhead / wiring harness/ ammeter circuit

4 If there is no or low output, make SURE you have good solid battery voltage to the blue wire at the field terminal. Once again, you should still have the blue field lead connected, the green wire unhooked, and the terminal on the alternator which you unhooked should be grounded. So take your meter and stick it into the "blue" connector with key in "run" and make sure you have battery voltage

5 If the charging voltage is low in the tests above, above, your alternator is NOT putting out much. From here you can decide to dig in and try and repair it, or just find a replacement.

5 IF the above tests show that the alternator can put out good "full field," now it's time to decide if it's field circuit wiring or the regulator. Hook the green field wire back up so all wiring is "normalized." Turn the key to "run" with engine OFF. Check voltage at the blue field wire at the alternator. This should be within a few tenths of a volt the same as battery.

Now unhook the regulator connector. BOTH terminals (blue and green) of the regulator connector should be close to battery voltage

One last test you can make is this:

Again the green alternator field wire should be hooked back up. Unhook the BLUE field wire this time, and clip the unhooked alternator terminal to ground. Devise a way to jumper across the two terminals in the unhooked regulator connector. This operation will again full field the alternator, but using the regulator wiring. Run the engine, and if the alternator puts out "full" at RPM, the wiring is OK

If this last test shows OK, replace the regulator.

Also, if you do NOT get yourself a proper Chrysler service manual. If you have one for your 74? Consider contacting AbodyJoe so we can upload it here to the site

If you do NOT have a shop manual, you can download the 72 manual here for free. The wiring is DIFFERENT from your 74, but the main charging circuit is SIMILAR

The thread is here:

Some of the links in the top of the thread are broken, but have been fixed later on

http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual,+download

Direct link to the 72 manual

[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/1972%20Plymouth%20Chassis%20Serv%20Man.pdf[/ame]
 
If you have the round-back alternator, a few of the 3 diodes can fail and it can still kind of work, but not enough to keep the battery charged. That was the problem with my 65 Newport. Since changing the alternator, no problems and I have TBI and an electronic fuel pump. Suggest you get a $15 voltmeter that plugs in the cigarette lighter as another diagnostic (Equuis on Amazon, several others). Should read ~14.5 V with engine running, ~12.5 V off. Ditto on get an electronic Vreg if you don't have one already.
 
67Dart273 said:
Well you have two choices:

1 Throw parts and money at the problem, and THEN make some tests
Click to expand...
This is why I came here, I rather not just throw money at it, I want to fix it the first time.
NEXT Some simple tests you can do

1 With engine running at fast idle to simulate low/ medium cruise, use an accurate meter to measure battery voltage right at the battery. When the engine/ battery/ regulator are warm, you should not have less than 13.5, not more than 14.5. 13.8---14.2 is optimum
Click to expand...
it starts off at 14.1, but drops fast down to 12.6
2 If not, find the green and blue "push on" terminals on the alternator field terminals. Unhook the green, and install a clip lead from that alternator field terminal to ground. Again with the car running, watch the ammeter/ voltmeter and gently bring up the RPM. This SHOULD put the alternator in a "full field" IE "full output" condition, so if the wiring is OK and the alternator is OK, it should "bury" the ammeter at "C" at some RPM, and start raising the battery voltage. Don't allow it to go over 16V or so
Click to expand...
It quickly jumps to 16+ volts, so it looks like the alternator is okay.
5 IF the above tests show that the alternator can put out good "full field," now it's time to decide if it's field circuit wiring or the regulator. Hook the green field wire back up so all wiring is "normalized." Turn the key to "run" with engine OFF. Check voltage at the blue field wire at the alternator. This should be within a few tenths of a volt the same as battery.
Click to expand...
nope, reads 10.6v
Now unhook the regulator connector. BOTH terminals (blue and green) of the regulator connector should be close to battery voltage

One last test you can make is this:

Again the green alternator field wire should be hooked back up. Unhook the BLUE field wire this time, and clip the unhooked alternator terminal to ground. Devise a way to jumper across the two terminals in the unhooked regulator connector. This operation will again full field the alternator, but using the regulator wiring. Run the engine, and if the alternator puts out "full" at RPM, the wiring is OK

If this last test shows OK, replace the regulator.
Click to expand...
yep, charges a plenty again, so looks like the regulator (which looks like new) is poo-poo. I guess you can't judge a book by it's cover.

thank you very much for your help

ps.
I only have an older haynes manual for this car, no factory service manual :(
 
make sure you have a bare metal on metal ground from the VR to the body, and that every ground is good while you are at it.
 
The 10.6V measurement is a PROBLEM

You need to find out what the deal is there and if possible, BEFORE you replace the regulator.

You might double--check this up at the ballast/ ignition feed.

There is only one switched 12V source coming through the bulkhead and depending on "options" and year, it powers

The "key side" of the ballast resistor

The blue field wire

The blue "I" terminal of the regulator

electric choke if used.

On some cars, other smog dooo-dads distributor solenoids, idle speed solenoids on the sixpack cars, etc.

So hook your meter to the "key side" of the ballast, key on, engine off. IF the voltage there is still LOW (different from battery) then you have a serious voltage drop problem.

Your top suspects are the

bulkhead connector

ignition switch connector

ignition switch

ammeter circuit and or the "in harness" splice

ONE LAST thing you might try before bolting on the new regulator

Get or make up a "heavy" (no14 or no12) clip lead, and hook it from the starter relay battery stud to the "key side" of the ballast. If that makes no difference, yup, sounds like the regulator.

IF you replace the regulator and it now OVERcharges (over voltage) then we'll go to work on the voltage drop problem (the 10V reading)
 
67Dart273 said:
The 10.6V measurement is a PROBLEM

You need to find out what the deal is there and if possible, BEFORE you replace the regulator.

You might double--check this up at the ballast/ ignition feed.

There is only one switched 12V source coming through the bulkhead and depending on "options" and year, it powers

The "key side" of the ballast resistor

The blue field wire

The blue "I" terminal of the regulator

electric choke if used.

On some cars, other smog dooo-dads distributor solenoids, idle speed solenoids on the sixpack cars, etc.

So hook your meter to the "key side" of the ballast, key on, engine off. IF the voltage there is still LOW (different from battery) then you have a serious voltage drop problem.

Your top suspects are the

bulkhead connector

ignition switch connector

ignition switch

ammeter circuit and or the "in harness" splice

ONE LAST thing you might try before bolting on the new regulator

Get or make up a "heavy" (no14 or no12) clip lead, and hook it from the starter relay battery stud to the "key side" of the ballast. If that makes no difference, yup, sounds like the regulator.

IF you replace the regulator and it now OVERcharges (over voltage) then we'll go to work on the voltage drop problem (the 10V reading)
Click to expand...

crap, didn't get a chance to read this first, replaced the voltage regulator, and not great news. Sometimes it will be around 13.1 at idle in park, and will bounce back down to 12.4 as I monkey around and test lights, fans, ect and the voltage will not always come back up unless I slightly rev the motor.

Sounds stupid, but what is the "key side" of the ballast wire? Isn't that what goes to the coil? Sorry, but eliminated those in my other cars (GM's) when updating charging systems, so not sure if that is what I am thinking.

thanks again
 
No the ballast is hooked on one side to the wire coming out of the bulkhead "the key side" IE the "ignition switch side." The other side hooks to coil positive. You want to make sure you are not doing that test on the coil side, which will read low.

Make absolutely SURE your fan belt is not slipping. It is also possible that the brushes in the alternator on "right on the verge" of making/ not making contact, something I should have mentioned.

You could confirm that by "full fielding the thing again, that is, unhook the green, clip the field terminal to ground, and then hold the engine at a fairly constant speed while watching the ammeter / and or / voltmeter. If the RPM is constant, and the output jumps around, it's either an alternator problem, or the main charging wire from the output, through the bulkhead and back to the battery has a bad condition

The "MAD" article gives a good rundown on this circuit. Down the page is a simplified diagram of the charging line

http://www.madelectrical.com/electricaltech/amp-gauges.shtml
 
Well, either I am doing this wrong (possible) or the car is playing tricks on me. Now when I do a jumper from the green terminal on the alternator to ground, it does not raise the volts at the battery, only 12.3 instead of the 16v I had earlier.
 
This sounds more like I was saying above, bad brushes or some other intermittent bad connections in the alternator
 
newguy,
Tell us the year and model of your car. Do you have the round-back or square-back alternator? Is there 1 field terminal or 2 field terminals? What does your Vreg look like and what type did you replace it with? Without these answers, we can't easily help you.

My guess is that your alternator is not grounding to the engine. Aluminum is like that. Run a big jumper from the alternator case to BATT- (black terminal), say use a jumper cable. If it puts out 14.5 V, that confirms the bad ground. If so, remove the alternator and sand where it bolts to the bracket, or just run an 8 awg wire permanently to the engine.
 
BillGrissom said:
newguy,
Tell us the year and model of your car. Do you have the round-back or square-back alternator? Is there 1 field terminal or 2 field terminals? What does your Vreg look like and what type did you replace it with? Without these answers, we can't easily help you.

My guess is that your alternator is not grounding to the engine. Aluminum is like that. Run a big jumper from the alternator case to BATT- (black terminal), say use a jumper cable. If it puts out 14.5 V, that confirms the bad ground. If so, remove the alternator and sand where it bolts to the bracket, or just run an 8 awg wire permanently to the engine.
Click to expand...

74 dart swinger, slant six, no idea between difference of round or square back alternator. Two field terminals.
 
"Round back" This one pictured is 69/ earlier because it has a grounded brush (one field terminal) but these "round backs" were used in 70 up to?? in isolated field (two field terminals) and are considered to be inferior at low RPM

2e3micw.jpg


"Square back" made only in isolated field (two field terminals) are considered better at low RPM

4
 
FWIW, I did the MAD electrical voltmeter switch (bypassing the ammeter), rewired & installed an alternator spec'd for a 1980's car (an '85 5th Ave, I think) along w/ the newer style Voltage Regulator & a few other things. I never, ever have trouble w/ charging anymore.

I'm no electrical expert, but I think that it's really worth taking the time & throwing 'a little time & money' at this project. I'm gonna do an even higher amperage alternator w/ perhaps an HEI Upgrade on the next project (maybe get some 1990s-21st Century technology going).

I'm for originality when it is aesthetic, but when it comes down to function, I've got no problem bumping a system, or component up a few decades.
 
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