Do i have a non-stock alternator? how to test?

you guys have been super helpful!!!! Thank you so much!

I have an 89 w/ a 90 4.0 transplanted into it by the previous owner. Now that i have the engine running correctly...i have noticed an electrical draw :doh:

Long story short i pulled the alternator and replaced it with a known good one and new battery..took me 3 tries but i got it one that fit. I originally robbed one off a 94 cherokee I have only to find out it was different. I then went and got a working one off a supposed 1990 and forgot to bring the correct one with me to compair....well i got home and discovered I have the same one as the 94...so i returned with the one off the jeep and the guys told me in there redneck ways that "that aint origional" on of the guys went in the back and came out with a re manufactured that was for a chevy 454..."that aint no jeep alternator u got der" but sure enough they were the same so i got that one and sure enough it bolted right in....


My Alternator looks original, brackets and all...jeep did make 2 types didn't they? Please some one has to know?

there is no fan type blade on mine like there is on my 94

After all this BS....



then noticed one of the wires was cut beyond the connectors (probably $$$ i didnt need to spend :doh: and time)...

after reconnecting wires

voltage gauge in jeep reads just above red with it running and lights off, and with lights on it drops some and as i drive more it drops more and more to the point the jeep will stop shifting, run really crappy, and eventually not run at all until the battery is charged.


I have not noticed any problems driving with the lights off...but im sure it is prolly drawing some power right?


my question is what is the series of tests i should preform w/ my meter? i tried searching and didn't have much luck......Thanks in advance

Up to 1990, a Delco (GM) alternator was OEM. 1984-1986 got a Delco 12SI, and 1987-1990 got the Delco CS-130.

Both were awfully common in GM vehicles, with the only principal differences being mounting (the 12SI and CS-130 refer to the size of the armature and the system used. Both are internally regulated - the 12SI uses two 1/4" spade lugs into a MOLEX plug, and the CS-130 uses a modified 4-pin Delphi Weatherpack.)

1991-up is a Nippondenso unit that is externally regulated - Chrysler built the regulator into the PCM. Better? Don't know.

There should be a fan mounted behind the pully on the Delco series - the SI and CS both had external fans (the later Delco AD series, and the ND units, have internal fans. However, alternators have pretty much always had fans - as have generators, going back to 1930 or so.)

Advice?

1) Repair that wire, particularly if it's off of the black Weatherpack connector. Those are the sense and energising leads for the internal regulator - a wiring fault there can mean no output from the alternator! A simple butt splice should be enough - since it's low in the engine bay, get the version that has heat shrink tubing on it, or get a section of heat shrink to put over the connexion once it's done.

2) Follow this series once you've repaired the wiring:
A) Measure and note the battery "resting" voltage (Key Off Engine Off)
B) Disable the ignition, monitor the battery voltage while a helper cranks the engine. The votlage will dip sharply then recover - it should recover to something well north of 9.6VDC (with 9.6VDC being the minimum acceptable.) DO NOT CRANK FOR MORE THAN FIFTEEN SECONDS.
C) Reconnect the igniton, let the starter motor cool off for ten minutes or so.
D) Start the engine. Note the engine running voltage at the battery. Compare is to the value noted in step A - it should be 0.5-1.0VDC higher. This indicates that the alternator is capable of charging while running the engine demands.
D1) If you are not noting a higher voltage at the battery terminals, work backwards. Check voltage at the starter motor relay screwpost (just behind the battery) and compare to the battery. If it's roughly the same there, check it at the back of the alternator (at the 6m/m screwpost on the back of the thing.) Correct wiring faults as indicated - the cable from the battery to the starter motor relay post sometimes corrodes internally, and there is a fusible link between the alternator and the starter motor relay.
E) If you note the higher voltage, continue to monitor while a helper turns on systems in the vehicle, one after the other. With the first voltage drop, increase idle speed to 1200-1300rpm or so (so you can get full output from the alternator.) Continue to turn systems on. Note when you get a sharp decrease in system voltage (down to battery voltage or less) and add up the demands placed upon the system.

You should now have a rough idea of the current output of the alternator (typically taken at 14.0VDC.)

Alternatively, take the thing out and take it to a local shop that does rewinds - they should have a bench that can really wring the thing out for you (the chain store benches only check voltage, and their rolling on-vehicle tester doesn't do much to test current peak - which is what you want.)

But - identify and repair that wiring fault first - as you've noted, it could be causing all of the headache for you.