Alternator or Battery?

Passport1

Passport1

Joined
Sep 17, 2012
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Location
A Barrier Island
BITOG diagnosticians work me up a differential Dx.

My elderly Volvo seems to have a charging problem. I've charged the battery and after driving awhile it cranks slow. I'm wary to drive it. Might leave me stranded.

Known history,

1992 Volvo 320K miles
Walmart Everstart battery circa 2/22
Alternator, Bosch 100amp, original
drive belt good
multimeter shows battery slightly below 12V. Might come up with a charge.
with engine running voltage drops slightly. Lights and heater blower on, drops to ~11.45 volts.

What does this geriatric patient need?
 
At idle an alternator needs to supply over 13 or more volts at minimum to supply the battery (to overcome resistance). Ideally you want to see over 14. If you lay your leads across the battery with the car running and it’s less than that, go at the alternator.

Frankly surprised that alternator lasted that long.
 
Besides rebuilding the alt also check for a parasitic draw. Can be something simple like a glove box light stays on, trunk light, even an aftermarket stereo.
 
If you go for the alternator get yours rebuilt or buy OEM. No parts house rebuilds unless you plan to let the car go in a short while.
 
LouC said:
Agreed big box auto parts store remans are very sketchy
Click to expand...

In June, I returned an O’Reilly alternator that had lasted 8 months/2,000 miles. VR went bad.

They gave me my money back (it was not the first time I had to use the warranty - more like 3rd) and went to NAPA. There is a lot of junk out there.
 
Believe these cars have a removable voltage regulator. There should then be a way to "full field" the alternator, briefly, for testing. It should make all the volts you want, and then some, 16-17 and growing, so don't do it for too long.
 
Bosch factory reman but make sure it properly grounded before replacing and that the wires going to it are in good shape with no resistance.

140.jpg
 
I've recently seen two alternators outputting lower voltage due to loose battery cables. I'd start with checking if the connections are clean and tight.
 
I recently had issues with my LeSabre keeping a battery charge. I had the battery tested, and it checked out really well. Tested my alternator with a voltmeter and discovered that, while it seems to be putting out the voltage to charge the battery, the voltage regulator seems to be shorting out in a way that is making charging intermittent. Looks like I’m going to need an alternator replacement. Think I’m going to bite the bullet and purchase a brand new Bosch. I can get one here in Ontario for $182 Canadian with free shipping.
 
In addition to the battery connections check the ground cable terminal on the engine end for clean tight connection and the ground connection from the engine to chassis. Been bit by both of those.
 
Also, upgrading the puny ground cable from the alternator to the block to 4 gauge will be quite beneficial. If you are interested in a swap that will net you better low RPM charging capabilities, the Ford 3G swap would definitely be worth looking into, you can even swap the OE dual belt pulley to the Ford 3G.
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