My 91 Samurai is acting abnormally when the headlights are turned on. The engine starts stuttering and bogging down when I try to gas it a little. Doesn't happen all the time, but doesn't seem to matter whether the engine is hot or cold. Runs fine with lights off. Lights do not dim, and the alt. light doesn't come on. Could this be a regulator issue? It is a royal pain in the ass to drive home from work at night when half the time I am trying not to have the engine bucking all over the place. HELP!

take a voltmeter and measure voltage at the battery.
should be |removethispart|@ 12.5V+ if fully charged.
when engine running, you should read |removethispart|@13.6V-14.4V. if more or less, probably something wrong, and this is where i replace the alternator.
if it's less, it's not charging the battery well enough- too high, and it'll burn your battery out.
i don't mess with replacing internal parts
i use rebuilt replacements w/lifetime warranty from my local parts place.
oh yea- check belt tension?
mabe

If you do the above, and suspect it's the alt, many parts stores will test the alt for free.

a mint battery should have 13.8 volts |removethispart|@ 2.2 volts per cell, alternator should be belting this voltage out, if its over charging the fault is the voltage regulator in externally regulated systems.

if the alternator is externally regulated with a electromechanical regulator then the solution could be as simple as sanding the contacts in the relays, and checking the resistance of the windings to make sure that they're not shorting out.

when the relays aren't working they can't earth out and bleed off the excess voltage.

but to be honest it sounds more to me like your coil is poked/not getting enough voltage/buggered ballast resistor, or maybe a high drain device in the coil feed circuit such as a electric fuel pump

something to ponder

a mint battery should have 13.8 volts |removethispart|@ 2.2 volts per cell, alternator should be belting this voltage out, if its over charging the fault is the voltage regulator in externally regulated systems.

if the alternator is externally regulated with a electromechanical regulator then the solution could be as simple as sanding the contacts in the relays, and checking the resistance of the windings to make sure that they're not shorting out.

when the relays aren't working they can't earth out and bleed off the excess voltage.

but to be honest it sounds more to me like your coil is poked/not getting enough voltage/buggered ballast resistor, or maybe a high drain device in the coil feed circuit such as a electric fuel pump

something to ponder

Just for a correction! A fully charged battery should be 12.6 volts. 2.1 volt per cell! Also your theory should be 13.2 volts not 13.8V!

a mint battery should have 13.8 volts |removethispart|@ 2.2 volts per cell, alternator should be belting this voltage out, if its over charging the fault is the voltage regulator in externally regulated systems.

if the alternator is externally regulated with a electromechanical regulator then the solution could be as simple as sanding the contacts in the relays, and checking the resistance of the windings to make sure that they're not shorting out.

when the relays aren't working they can't earth out and bleed off the excess voltage.

but to be honest it sounds more to me like your coil is poked/not getting enough voltage/buggered ballast resistor, or maybe a high drain device in the coil feed circuit such as a electric fuel pump

something to ponder

First of all, lets point out that you just used a word which I haven't heard in over 17 years..."MINT"
Here is an example.........."Dude, that DYNO freestyle bike is MINT! Where did you get that FRESH bash guard from?"

Could be a bad relay also. Could try pulling fuses to isolate which circuit... from there...divide and conquer.

should go on a trip to New Zealand sometime and widen the slang section in your vocabulary with lots of "lush" expressions   

should go on a trip to New Zealand sometime and widen the slang section in your vocabulary with lots of "lush" expressions  

Toche     

Come down here to Bama and you can learn:

Pass th' frickin grits, Ya'll

just to qualify my response:
i assumed the alternator is internally regulated.
i don't mess around with replacing internal parts on alternators or starters, i just replace the whole thing.
much faster, but more expensive.
i admire the person that makes those repairs.

Quote from: Mike-e on July 01, 2008, 04:36:33 PM

a mint battery should have 13.8 volts ...

Just for a correction! A fully charged battery should be 12.6 volts. 2.1 volt per cell! Also your theory should be 13.2 volts not 13.8V!

Just for further elaboration...
12.66 volts = fully charged,
12.45 volts = 75% charged,
12.24 volts = 50% charged, and
12.06 volts = 25% charged.

So if your 12 volt battery reads 12v, it's dead!
I love it.

Just for further elaboration...
12.66 volts = fully charged,
12.45 volts = 75% charged,
12.24 volts = 50% charged, and
12.06 volts = 25% charged.

So if your 12 volt battery reads 12v, it's dead!
I love it.

FWIW, I wouldn't get too excited if my voltmeter didn't give those exact readings.  5% tolerance in the meter readings can give more than 1/5 volt of error.  I would bet that most cheap meters are not 5% accurate, especially after a few years of use.  Even precision meters must be checked periodically for accuracy.  I have a $200 digital meter that I know is off a bit.  It hasn't been calibrated for over 10 years.

tatterdemons-
now look what you started!
have you figured anything out?

Or... you could just throw in a new alternator and hope that solves it. Worse case, you have a spare?  I think this thread just gave me a headache!

-Adam

I changed out the alternator, and nothing has changed. I also increased the idle speed just a hair. No good. This is challenging.