CO951

I was driving how yesterday and the ! light came on. I looked and the volt meter was reading about 10 and the light for that was on. Since I was 25 miles from home, I kept driving. When it finally started run erratic I pulled into a Checker Auto and the battery was so low I couldn't roll up the windows. I took the battery in for them to charge and their charger/tester said that the battery was bad. I'm going to get a new battery this afternoon, but my guess is that the battery was not the initial problem. My question is, how do I tell if the problem is the alternator, regulator or other problem? With a fresh battery would it be safe to drive it the five miles home? Thanks!

Jfrahm

With a charged battery you should make it home, or any distance if the alternator is also working.

If it discharges the new battery you have a charging problem, it might be the voltage regulator (which also houses the brushes) or the belt could be slipping or there could be other issues with the alternator.

Drive it home and see if it's charging.
-Joel.

theiceman

the regulator is built into the alternator anyway .. if you are reading 10 volts your alternator is pooched.. see if you can get it rebuilt, may be worthwhile just getting one from a wreckers.

m73m95

When mine goes out, I'm going to try this.

These are easier to find if you can't wait a week for a replacement to ship.

https://rennlist.com/forums/944-turb...eted-pics.html

bearone

if checker didn't charge the batt before testing, the batt may be good.
the voltmeter isn't accurate unless it's calibrated to a good dvm but the key is, it died and that's a voltage issue.

with no lights, the fuel pump still draws 5a and if the batt gets low, it'll finely kill the motor.

get the batt charged with a 15a charge and take it back to checker, running and see what they say.

i'd suspect a bad vr(worn brushes) and checker used to carry reman bosch alternators.

CO951

Checker did charge the battery as part of the testing. I took the battery back to my Porsche mechanic who sold me the battery and he hooked a tester up to it and the voltage held rock steady with a load on it. He said there is nothing wrong with the battery. I think Checker was just trying to sell me a battery. With proper light I confirmed that the belt is still good, so it looks to be either the voltage regulator or the alternator. I'm considering trying that smaller alternator, if I need to replace it.

whalebird

Put a voltage regulator on it ($25). Don't rule out a battery after that though. If a battery at any point in time reads less than twelve volts its toast - simple rule. Seldom will they come back.

bearone

i'm not sure what your mech means "rock steady".

a hi rate discharge test should pull the batt down, simulating a load but shouldn't pull down near 10v and only takes about 10 seconds.

if checker said it's bad and the guy who sold it to you says it's good, maybe your mech doesn't want to eat the battery cost.

CO951

What I mean is the battery read over 12v on the tester. When he put a load on it it droped down to about 12v and help steady on that for the full 10-15 sec.

I would trust my mechanics before I would trust Checker, anytime.

I got the alternator pulled from the car. I cleaned it out and put a new regulator on it, but it failed when I had both Auto Zone & Checker test it. I was thinking about using that Nissan alternator like in that previous link, but that one is about $60 more at both of the parts stores.

Jfrahm

I have had very little luck with the testing at Autozone/Checker, they are pretty good at doing it wrong.

mikal

I too have a problem in this area. My battery went dead after installing a new one. I charged it up and did a parasitic draw test. 730 ma.............yep that big. Tested the wifes civic and that drew 20. So I have a problem Any ideas where. Next job will be pulling fuses. The LAST thing I want to do is replace the alternator reg.....help!

Tiger03447

Dear Stig: When you went to AZ for your alternator check, did you get a printout as to why it failed? They should have done that, and the tester should have also given you a printout as to the numbers of the voltage output and the ripple volts. It's called "test results" on the alternator testing device, if you want to go back there. If you put in a new regulator/brush unit, you should be getting between 13.5 and 15.5 volts out of the alternator. Unless there is a short in the stator or rotor windings, or if a diode is gone, those would be the only problem areas left to check out. Might be best to get the tiny unit..A Honda Fit also uses a tiny one too, both are Nippendenso units. Many track guys use one of these on various race cars, because of their compactness and lighter weight. What year Nissan did you check on? Keep us posted as to the findings on your quest. Thanks.

bearone

i was having the same issues at one point & it turned out to be the door lock or window switch was bad but showed good continuity.
i changed out the switch & the pulling down the batt stopped

another time, i had a shop replace the alternator, it was a bad one & the shop replaced it.

are you checking by pulling each fuse to see where the high draw is coming from??

Ish_944

Are you sure about 15.5 volts? I'm actually getting that much after ~30s of turning the engine on. Before that it reads 14.7 volts. I consider the lower to be appropriate and the 15.5 too high.
Don't you think that 15.5 could damage the battery?

CO951

It looks like I didn't do a follow up on this old thread. Changing the regulator didn't help. I ended up replacing the alternator with a used one that tested good and that solved my problem.