possible bad alternator????

[grantf]

To add to my past problem solving adventures, I now have a charging issue.

I have a new battery shows 13.3 when charged but drains while the car is running (11.7). So what is the best way to check the alternator? I really do not wish to throw $$$ at the problem.

1978 280Z

[Z Tyler Z]

Take it to any auto chain and they'll test it, generally for free too. I used Autozone when I had this problem.

[sblake01]

You can test is yourself if you have a voltmeter. Personally, the thought watching some kid at Autozone test anything for me makes my skin crawl:

[grantf]

You can test is yourself if you have a voltmeter. Personally, the thought watching some kid at Autozone test anything for me makes my skin crawl:

agreed As stated above I have performed this test (failed), just whanted to know what else might be a cause......

I am bringing my part to a store but not autozone, It's going to an old store down the street that actually has a machine shop, really funky store, it's been around since the war of 1812 I think or maybe the fall of Rome not sure, but they don't sell bling crap and the counters are covered with years of grime.

[ajmcforester]

If your skin crawls from them testing it use the loan a tool program and test it your self. They let you help them out and you can make sure they do it right. You can also bring just the alternator in, they can test it, just make sure they hook it up right. If you bring just the alternator in call before you go they only have one or two people that know how to test out of the car. Don't weight to long you can kill a good battery with a bad alternator and visa-versa, they are like your liver and kidneys if one goes bad you have a problem with the other.

For a while their Auto Zone had a rebuild kits for the alternators, something to look into.

[sblake01]

My skin crawls from just the thought of them testing it for me. I wouldn't actually let them do it. I have the tools/skills and I really don't need their help. Testing an alternator isn't rocket science. I used to be able to get rebuild kits for these altenators from a friend of mine that had a shop but they went NLA a couple of years ago.

Edited February 2, 2010 by sblake01

[grantf]

ok so shucks tested it and it passed! then I brought it to the "old school" shop and it failed! got it back covered in soot :tapemouth :mad:

so now I can rebuild it my self or $$$ a new one. :mad: :mad: :mad:

[sblake01]

grantf, those are usually the best shops! Old guy with a cigar, ditry counters, fan belt gauge hanging on the wall, etc. Little by little, those places are disappearing. Make sure you get the internally regulated alternator as 78 was the first year for that. The internal reuglator module is what generally goes bad in them. I just don't know where to find that part anymore.

[grantf]

got new alternator, it's only generating 12.6 and no change at 2400 rpms

[ajmcforester]

Check the regulator and were did you get the alternator? I'd get the original rebuilt if it is reasonable. I don't seem to have good luck otherwise

[sblake01]

Check the regulator and were did you get the alternator? I'd get the original rebuilt if it is reasonable. I don't seem to have good luck otherwise

A 1978 280Z alternator is internally regulated.

got new alternator, it's only generating 12.6 and no change at 2400 rpms

If you ran the test as outlined above, your 'new' alternator is no good. It does happen. Edited February 3, 2010 by sblake01

[ajmcforester]

I worked for a little while at a parts store we had more internally regulated alternators come back, because the rebuilds didn't replace the regulator that is why I've had bad luck with getting alternators, and I just rebuild my own instead. If I was him ether rebuild the original one or take it to some one good to do it. If you return it for another one ask them to test it I did that with everyone before I gave it to them. I found they would have 20% not to spec on the shelf as rebuilt (my manager didn't like how many rebuilds I sent back, but at least we were less likely to have a return that way).

The last alternator I purchased was from a junk yard for rebuild because the original regulator in my truck reversed polarity and burned out all the wires inside. I rebuilt the junk yard one for $20 in parts and $5 for the alternator with about 2 hours of work.