No Charging from Alt 1972 Z

[ajmcforester]

Try this with the car not running but in the on position and the positive terminal disconnected from the battery. Disconnect the posative feed from the alternator and run a wire from the batter positive to the alternator wire and test to see if you get power.

[stevef1972z]

Took the alt off yet again and took it to two different parts stores for testing. The alt is putting out 14.68 volts. Now I know beyond a doubt it is not the alt, so it is either wiring or votage reg.

[FastWoman]

You need to see where your voltage drops are with the alternator in place in the running engine. That will tell you where you've not got continuity. Connect the (-) probe of your multimeter to the case of the alternator (E terminal), and probe the following:

-- Engine block (should be almost exactly 0 V)

-- (-) terminal of battery (should be almost exactly 0 V)

-- (+) post of alternator (should be approx 13.5 - 14.5 V if voltage regulator is regulating correctly)

-- each side of the fusible link (should be same voltage as (+) post of alternator)

-- (+) post of battery (in theory should be the same as alternator pos post, but might be a fraction of a volt lower)

Any deviation from your expected voltages will reveal the trouble spot(s). Wherever you've got a suspect connection, measure the voltage across it. It should be 0 V. If you have a voltage greater than that, you've got a bad connection.

[EScanlon]

The fusible link for a 72 Z is between the Starter's POSITIVE Batterty connection and the wiring harness. You should be able to see it below the battery going to the wiring harness on the side of the engine bay.

As far as I know, there is only ONE fusible link in the 72's. If your car has the Intermittent Wiper (4 stops on the Comb Sw. ON-INT-LO-HI) then your car has 73 wiring and not 72.

Check the connections at the battery, make sure you've cleaned the clamps and posts, also the grounds. You've added grounds and changed components, that's all good, just make sure everything is proper. Is the V/R mounted on the firewall or is it floating loose? How about the Amp Gauge? Good connections there?

Also, I remember reading about another Z's Alternator NOT putting out proper voltage unless a certain RPM was maintained, are you idling or are you checking at higher RPM's?

Are you making all these checks with all electrical systems off?

How about your battery, is it fully charged? A "new" battery oftentimes needs a good external charger to bring it up to voltage, your Alternator will normally re-charge what you take out, but it takes forever to bring a Battery up to full voltage.

FWIW

E

[stevef1972z]

Problem Fixed

After going through the entire charging system, 3 alt, 3 voltage regulators, every wire, every connection, every fuse and adding grounds plus cleaning all the factory grounds it is charging. I decided to take the old voltage regulator that had been on the car since the 1980's (at least) and see if I could make it work. I took it apart, melted off the old solder, replace the wires, re-soldered, took the plug apart, replaced the wires and connectors. I hooked it back up with the alt that I had tested yesterday and low and behold the amp guage swung to the + side for the first time in months!

I have no idea if the new voltage regulator is good or not, don't care now I have charging. Went on several 15 mile runs, and it charged like it was supposed to, even get the bob when the directionals are on at a stop light.

Thank you for you assistance, all the testing and ideas may not have solved the problem, but I bet this car hasn't had the electrical system in this good of shape in since it left the factory.

[FastWoman]

Just make sure your alternator is running at the right voltage! You don't want anything higher than maybe 14.6V. (Even that's a bit high, but I think Datsun liked to run their voltages high-ish.)

[manuel59]

I sort of had a smiliar problem and it turned out to be a bad pully.