alternator issues

[mazda-nissan]

I have a 92 mazda b2200 with a nissan sd22 in her. She runs great, but I need an alternator for it. I'm only finding lil baby 35 -50 amp jobbers for it. I put a real solid gel battery in and seems to drain from the battery instead of charging it. The P.O.S. rebuilt stock aternator only puts out 30 amps. Anybody have any suggestions for a straight swap from anything serious like an 85-125 amp unit, maybe from a gm or something? I get the feeling this is why the previous owner sold it, as I found a couple belts in the back seat area. Thanks from the new guy

[asavage]

If you don't need the vacuum pump feature of the Hitachi LR-series alternators, you can put on any alternator you like.

If you want to use someone else's alternator and still have vacuum for your brake booster, you can add a separate electrically-operated vacuum pump.

If you need the OEM-style alternator driven mechanical vacuum pump, your stock Hitachi LR150 alternator is rated for 50A output -- under test conditions, which means full-field voltage at a specific output voltage. If you are testing at a higher voltage than the rating, the current will drop off.

IMO, 50A is plenty, unless you have some special electrical loads. Certainly, 50A is enough for the stock SD setup and is not especially overstressed. Even the all-the-bells-and-whistles luxury all-electric Maxima has only a 60A alternator. Do you have a big winch or a huge stereo? A rack of high-wattage lights on a roll bar? Those are situations where a higher-output alternator would be useful.

The simplest swap is for a LR160 alternator from a Maxima (LD28) diesel. It is a bolt-on, with a single wire different (the LR160 has an extra terminal that would remain unused in your swap). The LR160 is a 60A unit. Much more information on the LR-series alternators is in Hitachi LR150 50A alternator thread and Hitachi LR160 60A alternator thread.

I have seen someone hang a second Delco alternator up above the injection pump, on a SD22 at the JY.

You might have a rebuilt alternator that has the common "broken diode" problem.