1973 GT550 Alternator Part #

[Vintageman]

ANyone know if there is a difference between Nippondenso alternators

31400-33110 vs 31400-33111

Partzilla show both obsolete but 31400-33111 was stated for GT550B and 31400-33110 for K-A. Why would B be different?

Thanks

[Alan H]

My books say 31400-33011 for J,K. 31400-33110 for L,M,A and 31400-33111 for B. Also the stator, brush springs, brush holders are different on the B models. Rest is all the same. I didn't realise there were so many differences but what they are only the japs know.

[jabcb]

Nippon Denso rotors for J/K had a design flaw that was corrected for subsequent model years.
See service bulletin: http://www.ozebook.com/compendium/techb ... mpress.pdf

[Alan H]

We live and learn. I hadn't seen that one. One of several I expect.
Thanks for that.
But I would expect that if the insulation to earth and the conductivity between the rotor rings is good, then it's OK, whatever the number.

[Vintageman]

Guys

Thanks,

All of the sudden I am not charging on my 1973 GT550. I did a crank job last year and maybe that is the point the issue occurred maybe not. The rotor is the original one, but has about 10 Ohms across it and no short to body. So thinking OK... maybe shorts when spinning due to inertia. Brushes have a lot of like left. Changed regulator (the OEM looked fine inside, but bought solid state, and new Battery. Did a simple diode test all diodes conduct forward and block reverse as they should at least with the voltage my meter applies. The yellow stator wires read 0 Ohms between them and no short to body. Wiring and connectors look good.

I haven't done the test per service manual where I apply jump in 12VDC directly to rotor brush and see if it charges that way. If it does not then stator or rotor I suppose

I was just going to buy a new stator but seams like subtle difference between them... like maybe my brush housing won't mount. I suppose I buy a couple I'll get quite acquainted with the difference and loss of money (what's new when owning these old girls).

I am an electrical engineer (write more software these days) and think I could hook up my O-Scope and figure this out (may have to). I wish the stator had an inductance value published I could check that versus 0 Ohms. Using DC meter I get very little charge on battery say 11.7V not running key on and 11.9V running but dropping. It may not be charging at all I suspect.

[Alan H]

The charging system is straightforward as you know and jabcb and myself went through them pretty thoroughly on another thread. Here - viewtopic.php?f=2&t=13030" onclick="window.open(this.href);return false;

If I haven't sent you a copy of a Suzuki service manual, pm me your email addy and I'll pop one 'in the post' FOC. Lots of info relevant to all models, but not later ones specifically. Charging basically same all through though.

[Vintageman]

Wow long post with no ending... was the R/R bad? A lot of common sense points

When I get some time I'll get Amp meter, volt meters, O'Scope and inductance meter (just curious) and a blower to keep engine cool while setting still and running.

So far the factory passive tests all check out OK. Maybe Start with applying DC power directly to rotors and look for AC out of stator fields. I bought new regulator but don't think it has the rectifier (I'll recheck). Still have the OEM electro-mechanical regulator and looks pristine inside. Probably was fine. Just need to find the time

Thanks

[Vintageman]

Found it! Recheck connection to brush to regulator . the green wire an no continuity. The chain cut 99.99999% of the way through the green wire that supplies power to the rotor brush. Just the green wire, the rest are pristine so I kludge fixed the green wire and all is well. This explain why it failed shortly after I changed the crankshaft... did route wire perfect enough

I must thank Jabcb and Alan H. I did have to spend a dime and they made recheck at the basics


I was thinking another way to test rotor is to apply 12VDC power across it and verify it turns into a good Magnet!. If not or weak I would say it is bad But, instead simply found the green wire cut by the chain!

[Alan H]

Well spotted. It's usually the basic stuff that causes the problems.