No charge alternator

[loyalematt]

I have a 90 Loyale 1.8L non turbo 4wd with a 5spd. It started with not responding to throttle with the headlights on and now it progressed to constantly. First thought was the voltage regulator in the alternator going out since the problem was under load. Replaced the alternator. No change. Ran a voltage test with the old and new alternator and get roughly 11 volts at the battery not running, then running with a jumpstart, and steady decline. My thoughts are running on battery alone. Also checked voltage output at the alternator and the fusible links which all stay steady with battery voltage running. Changed the battery and got it home, but still only show 12.2 volts running. I should be atleast over 13V,and it normally charges around 14.3V. Best I can tell, all grounds are good and in the proper locations. Ran fine up until about 2 weeks ago after changing rear axle out. Any ideas?

Edited November 15, 2017 by loyalematt

[DaveT]

How many miles on the original alternator?  Every one I've had has worn out a brush right around 150K.

 

You are describing no alternator output with the readings you list.

 

Some reference points: 

 

Brand new condition non abused battery -

Fully charged, resting battery = 12.6V

Fully discharged resting battery = 12.0V

 

Anything lower than 12.0 is harmful to a battery.

 

13.8 would be absolutely the minimum for any charging to happen.  13.8 is typical float voltage, and car charging systems are not float chargers - they have to put more power back into the battery in too short of time to be truly float.

 

Rear axle change is coincidence, unless you did something to the electrical system under the hood..

 

I've read a lot of stories on here about people buying bad alternators.  I've always rebuilt them.

[loyalematt]

I will give exchanging the alternator again a try. It was a rebuilt duralast alternator from autozone. I know its not unheard of to get a bad one out of the box. Just didnt think it was as common as it seems from other threads ive read here. The strangest part of the dilemma is the old battery was a value power from walmart that was manufactured 1 year ago. With that battery even the replaced alt. would run at 11V and steadily decline. When I replaced the battery with a new duralast gold, from the time I dropped it in and drove it all the way home in the dark with lights and heater going, it stayed constant at 12.2V. I know thats not enough to recharge the battery but why no decline in voltage with a different battery? Battery reserve?

[loyalematt]

And to answer the question about original miles on the alternator. I have no idea but it was also a duralast alternator that was on it given the sticker markings and part number so the original was replaced before I got the car.

[DaveT]

The brand new battery was likely fully charged. For a while, it would hold fairly steady voltage. LA batteries have a moderately flat discharge curve until depleted. The old battery had already been abused by running until discharged. It may or may not recover if fully charged. Starting batteries don't handle deep discharges well. They should survive a few, but each reduces life.

 

In addition to checking that the output wire has a good connection, check the 2 small wires on the T shaped connector.

[loyalematt]

I even ran a jumper wire from the batt terminal on the alternator to the + battery terminal. No change. The T plug on mine only has 1 wire connected. Has been that way since I got it and ran ok.

[DaveT]

That is odd. I've had several and they always have 2 wires. Not sure what missing one could cause for trouble, or why one would work without one. Never had trouble to investigate enough to find out.

[Gloyale]

 The T plug on mine only has 1 wire connected. Has been that way since I got it and ran ok.

 

Well there ya go.

 

The white/red wire needs to be hooked up for sure.  It's the "charge" light circuit, and provides a resitance load to excite the ALT.  It should be the upright leg of the "T-connector".   Fuji labels this always as "L" terminal or "Lamp"

 

The other wire, Black/white probably, needs to be connected to a battery 12v + source also.  Switched power would also be ok, just needs to see system voltage at that wire, the horizontal "top" of the "T-connector"  This is the "sense" or "system" wire that the voltage regulator uses to monitor system voltage.  Always labeled by Fuji a "S" terminal.

Edited November 15, 2017 by Gloyale

[loyalematt]

I didnt see your reply GLoyale until after but the problem is resolved. Have a 92 parts car and snipped all 3 alt wires from its harness. Reconnected into the 90's harness with all attached and wham! Now have 14.25V at idle. Appreciate the responses and help.