I have a bit of a problem. I have a 97 S-10 Blazer LS with 4.3. Today
on the way to work the little battery sym poped up. The gauge read
just under 12 V. To me this sounds like a alt. or battery problem.
Does anyone have a opinion. I was able to restart it and drive it home
with no light and the gauge dropped a bit more.
Local store sell 2 compatable alts. One is $30 (? amps) and the other
is $157 (100 amps). Both are refurbs. Is the regualator built in the
Your alt is bad (even if the battery was bad once the engine started the alt
would produce 13+ volts) just get another alt and change it. Be sure to
unhook the battery before you do anything that red lead at the back carries
battery voltage and will give you a very sizeable spark if it touches
anything (been there done that). When you pull the old one you will see a
set of numbers stamped on it (I.e. 12v 100amp) make sure the new one is the
same amp or larger (must be same physically size). Two bolts hold it on and
a large wrench on the belt adjuster pulley (bolt will be in the center of
the pulley) that has the spring will allow you to move the pulley up and
take off the belt. Make sure you do charge the battery before you hook up
the new alt a sudden heavy load on the new alt can burn it out quickly. The
alt will come with an instruction sheet that will tell you which battery
cable to hook up first. You may also want to take the opportunity to change
the belt at the same time since you already have it off. Easy should take
you 15 min to change it.
You are looking for a output voltage of ~13.7 volts to a max of 14.5 from
the new alt. You can use the dash volt gauge or if you have one, a hand
held volt meter to test all voltages. I get my parts from pep boys with
lifetime guarantees (I keep my cars for a min of 20 yrs) so call around.
The alt is one unit everything is internal gone are the days of a firewall
mounted voltage regulator... Basically the alt has a plug that has two
leads (black and brown I think) on it, one sends power to the volt gauge (or
light) and the other brings power back from the gauge (or light) so the
internal regulator senses the volt difference (resistance) of the gauge (or
light) and compares it to the battery voltage (large red lead at rear) and
charge output amperage is based on this number. In most cases it will be a
bad alt but can be (in very few cases) a bad gauge or instrument cluster
connection. Sometimes the plug at the top of the alt will corrode and loose
connection which confuses the alt and it will full field and send full power
to the battery cooking it. Best way to fix this is to clean the contacts on
the plug or change it with a new one. More information then you needed but
it should be an easy fix.
Check your battery connections, for corosion and tightness. The GM alternators
use Avalanche diodes that do not like current surges
from a sparking contact. One of the main reasons that the alternator goes,
unless you have a bad voltage regulator.
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