A clamp on ammeter is nice to have (make sure its DC) but the wrong tool since you won't be able to use it while you're driving. You want one of those digital voltmeters that plugs into your cigarette lighter.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Well right now I'm driving without any electronics running. I want to go through and turn them on one by one to see how that affects amperage outputs. I do have a cigarette adapter voltage monitor on order as well.

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Own:
1970 Mercedes 250c, 1976 International Scout II, 1982 Mercedes 240d, 1997 Honda Accord Wagon, 1998 Acura Integra Type-R, 2009 Mazda5.
Owned:
1974 International 100 pickup, 1975 International Scout II, 1981 Mercedes 240d, 1985 Mercedes 300SD, 1988 Honda Accord, 1988 Ford Thunderbird, 1991 Honda Accord, 1996 Geo Metro, 1996 Ford F150, 1996 Dodge Grand Caravan, 1997 Honda Accord, 2003 Acura TL-S, 2003 Yamaha V-star.

It sounds like you have it sorted with a charging voltage of 14.39

If you want to experiment further, get yourself a clamp meter.

You can do this by placing the clamp ammeter on your D+ and should get 500ma approx (stator field diodes) which will disapear once the alternator is spinning. If you place it on the B+ you will get output from power diodes.

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1995 E300 Diesel

To monitor charge current of your alternator, clamp-on ammeter should be on the B+ terminal, not D+. I'd like to see you do that while you drive.

What you want to do is monitor voltage while you drive. It should be pretty steady. If you see a sudden dip in voltage, pull over and investigate with your ammeter.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

B1 correct. By my 6th day of work and three young children pulling at my ankles, my mind begins to shut down.

If you measure current on D+ you will measure 500ma approx(stator field diodes) and this will disapear once the alternator is spinning. If you measure B+ you will get the output from the power diodes.

It would be nice if car manufactures kept this method in cars. I have two old English cars that both have an ammeter on the dash as oppose to an idiot light 'battery light'. It's so simple, you rev the engine the needle moves.

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1995 E300 Diesel

My old dodge trucks have the amp meter... only goes to 30 though. I'm guessing a meter large enough to handle the entire load of the alternator on modern vehicles would be heavy, and expensive. although a remote inductive sensor could give an indication of function, it would not be the same as an actual amp meter.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Do you have a wiring diagram for your truck? My guess is that it's between alternator and battery and measuring charge current, not vehicle elec load.

An inductive ammeter is an actual ammeter and measures the same thing- current, it just uses advance technology.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

It's been I guess five days now and alternator #4 is still holding. I've been driving the car using minimal electrics and I think that may be a factor. My cigarette lighter voltmeter came in and I've been playing with it a bit, turning on different electrical systems and seeing what happens. The biggest drop by far is turning on the cabin blower motor. All my testing was done at freeway speeds. It's a 240d so I've got three fan speed positions. Turning from "off" to "1" results in a drop from 14.18vdc to 13.80vdc. I thought that was excessive considering that turning on my headlights drops from 14.18vdc to 14.07vdc. Curiously, turning the fan speed to "2" only drops from 13.80vdc (@ speed setting "1") to a 13.70.vdc. Then turning the fan speed to "3" results in another large drop, to 13.35vdc. Turning on the A/C results in another .05vdc lost, so the electromagnetic clutch seems to not be a culprit. Eventually the aux fan turns on but because I've not isolated it I don't know exactly when it's happening so I don't have reliable readings for it.

Alternator #4 has expired. I don't know what to say.

Disconnect the battery and pull the regulator. Check for any corrosion on the grounded face that contacts the alternator housing. Also, check the alternator housing itself. (No, tight screws are not a good enough test.)

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Sam

84 300SD 350K+ miles ( Blue Belle )

These are all autozone reman alternators?

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This post brought to you by Carl's Jr.

4 alternators went bad? Can't believe it's bad luck!

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Yeah, they're all AZ remans. They're warranty replacements so no cash just time. And given my apparent lack of troubleshooting skills, my time is pretty worthless. Ha! Anyway, I'm going to replace every major cable I can in this damn thing I guess. No clue what to do other than throw parts at it. I've got an alt here sitting on the bench I can reman myself. Any opinion on manufacturers for the guts of it?

Bring the alternator into Autozone to have it tested to verify that it is bad. Have you done that with the first 3 alts?

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Yeah, they test em to verify before accepting them back.