Voltage regulator smoking

[MuirBound]

In the process of bringing my '69 back to life and when I went to start it the voltage reg started smoking. Took the case off and saw one of the wires had been melted. I know the common thought may be that it was a bad voltage reg. Does anyone have any ideas why this may been happening? I don't want to purchase a new regulator if there is potential this will happen again. Any advise will help as this thing is almost a complete project and this is a big hang up. Thanks guys.

[Esteban]

This is totally an isolated incident and you'll be fine with the new regulator.

Any voltage regulator for a Datsun/Nissan of the 70s will do the work. I just checked at Rockauto and they have this for instance:

http://www.rockauto.com/catalog/moreinf ... 486&jpid=2

The above part will fit any Datsun from a 1968 520 Pickup to a Datsun 240Z up to 1973. Voltage regulators have little to do with the output of the alternator, and most of the alternators were 50 amps or less. Original Nissan Patrol was only 35 amps.

Old regulators control the voltage applied to the rotor of the alternator, with electro-mechanical devices. No electronics involved in the old ones. If you get a new replacement, most probably is going to be with electronics inside.

I can only think of one condition on the alternator that can cause trouble with the voltage regulator, and it is if the rotor is shorted (extremely rare in any car). You can do a simple test to check this condition. There should be a terminal marked F (for field). With the connector disconnected at the alternator, measure the resistance between F and ground. You should get around 4 to 5 ohms. If you have 0, then the rotor is shorted inside, and that can cause some trouble to the voltage regulator.

Check this topic to identify the cables at the alternator, and some tests as well:

http://www.60patrol.com/forum/viewtopic ... hes#p23984

Please post a picture of the regulator for the post mortem analysis.

[MuirBound]

Thank you so much that is very helpful, thank for for taking the time to post all that info for me. I will get the new regulator and hopefully fire this beast up soon. It's been sitting 20 years this June and just recently made a push to get it going again. We checked and replaced hoses, cleaned gas tank, installed new fuel filter, new battery and cables. And three times now when we went to start it, voltage reg smoked, other than that, the engine turned and created vacuum. Just can't get it to fire up and stay alive. Anything I'm missing (aside from faulty voltage regulator)?

[RMP&O]

FYI, the early voltage regulators up to about 1966 are adjustable.

Cheers

[Esteban]

..And three times now when we went to start it, voltage reg smoked, other than that, the engine turned and created vacuum. Just can't get it to fire up and stay alive. Anything I'm missing (aside from faulty voltage regulator)?

Try starting the engine with the alternator and voltage regulator disconnected. The battery alone will be able to keep the engine running for some time. At least this way you can be sure that the alternator/regulator system is not preventing your engine from running.