ok heres the deal, car died on me and the battery is less than a month old so i ordered a alternator and installed it. put it in and the battery still isnt charging. (put a meter on the battery terminals and get batt voltage at idle)

found out the battery light WASNT coming on at all. refered to the helms, step 1 was check the alternator fuse, go figure it was bad. put it in and now the battery light comes on with the ignition on (engine not running) but now the light stays on while its running.

so going by the helms i keep going, with the connector off the alt i checked for battery voltage at pin 1 and thats good. the battery light goes out with the connector out and then i shorted pin 3 to ground and it came on so that was good.

after this i checked the frame of the alternator to ground and theres no resistance then i checked it to the neg batt terminal also no resistance, checked the neg cable to ground, no resistance. i checked the output of the alt to the fuse box and there was no resistance. output of the alt to the pos terminal and again no resistance.

thinking it might be the ECU i tried my old stock obd2 p75 ecu, no codes (was looking for code 20, ELD) and it made no difference. i still havent tried ohming the line from the ecu to the C pin on the alternator yet.

i dunno im at a loss here, the alt fuse hasnt blown again and even with a fully charged battery the light still stays on when the engine runs. maybe the fuse was the only problem and maybe the alternator i put in is bad but it would have to be completely dead as im getting NO output from it. it came with all kinds of voltage and current output checks that passed great with it (reman from advance auto)

when i go home im going to try the stupid stuff again, retension the belt, try the voltage at higher RPMs etc but please if you have any thoughts im gettin pretty desperate.

 

- the car should register slightly more volts across the battery terminals when the car is running, if it does the alternator is charging the batt. if volts dive when you start it, there is no charging. alternators usually have a high and low charge so that the car isnt stalling out on idle from a heavy magnetic field drawing the motor down. rev it up to 4k or so and watch the meter.

- if any alternator is charging, it usually has a slight magnetic field at the back center of the housing, detectable with a wrench or screwdriver.


whats the situation with yours in those regards?

 

there is no charging. its not that its weak, its just not there. i get dropping battery voltage with the car running, the more i turn on the faster the battery drops.

i still havent checked the last few things out yet so i dunno but im gonna be pissed if the re-man alt. i bought is junk.

 

check the alternator fuse

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JCushing &raquo;</TD></TR><TR><TD CLASS="quote">found out the battery light WASNT coming on at all. refered to the helms, step 1 was check the alternator fuse, go figure it was bad. put it in and now the battery light comes on with the ignition on (engine not running) but now the light stays on while its running.
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is there voltage from the alternator lug to chassis ground? if not then i would bet your problem is in the wiring plug prior to the alternator. the likelyhood of two bad alternators (your old one and the new one) is kinda iffy to me.

got a schematic diagram for the charging system pinouts?

 

yeah i got a helms i checked most of the wires but i have more to check, all i checked were resistances, i did not check voltage drops.

and again im not sure that the first alternator was bad. like i said i didnt find the bad alt fuse till after i swapped out the alternator

 

well, excessive currents blow fuses, and theyre caused by voltage spikes or lack of resistance. a faulty voltage regulator, power wire grounding out or burned up resistors are what im expecting it to be.

screw in anything new lately? its easy to get wires pinched under interior panels, seatrails, dashboards and so forth..

 

well i put the old alternator back in, guess what, it worked. 14.5 volts at idle

theres a lesson to ya, check fuses first, and reman alternators suck

 

all's well that ends well