95 Geo Prism head lights, dash board lights go dim, slows in power, check engine light comes on.
does the alt light glow, keyon (aka. chargelamp)? if not BAD !
fix that FIRST !
This is really simple in most cases.
it's a system, called a charge system.
it has 3 /4 parts.
1: Alternator must spin about 2 times crank speed.
if the engine RPM is 400 , the Alternator will give UP.
so first engine RPM 800 then i strobe the alt pulley, oops belt slips, mine runs at 1.8 ratio or 1400 rpm at alt pulley.
for a DIY is the belt tight?
2: is engine RPM at 800? no , fix that first.
3: RPM good.
The system now is ALT wires and battery. 3 things.
if the ALT is good and the battery is good (tested)
then it must be what. the wires.
The alt can put out 50+ amps..
there are at least 4 wires on most alts and any can fail.
1: big red. (huge charge wire,, or the inline fuse blown.
2: ground, old cars , and for sure in the SALT belt the gound fails
do to RUST, or better word, Corrosion and both.
alum and steel (iron) both corroded, add salt and its worses
in 2 ways corrosion and electrolysis. (google that)
so the ALT case must be grounded to the engine. 100% perfect
then engine ground stap to battery minus. if not the ALT will FAIL.
now we land on 2 more wires, most cars.
that rear connector.
1 is ignition sense wire, if open alt goes nuts.
2: is the idiot lamp. if lamp is bad, (dead) the alt can shut down.
this lamp creates boot up , initial excitation current, so the ALT can start up. most ALTS have no residual magetism to start up.
so it needs a bias circuit, to do that.
and guess what, each brand of ALT uses different parts here.
EVEN REBUILTS, so best practice, is to assume the lamp
must be good, and fix that first (early cars, ) new cars the ECU
runs the alt and is 10x smarter, not this car. at all.
no lie , testing the alt, in car is hard.
many times the ALt just shuts down. (faults)
and with zero current flow, you can not find the voltage drop
that precipitate that fall out/
there is a method but is risky , on car, called "full fielding"
it can blow up electronics,. so that is my warning.
does this help?
one other crazy failure
some cars have DRL , in uSA , some, in canada , many.
i fix them all. but the DRL in many cars, (this year)
connects the alternator, and DRL burns up and kills the ALT.
the reason DRL uses the charge lamp is easy
it shuts down DRL any time the Charge lamp is dead.
allowing more battery volteage (& current) to start, HEADLAMPS off.
same with cruise control some drop out , if change lamp is on.
to understand all this , its all in the manual. (parts effected)
at alldata dot com.
Aug 02, 2012 |
1995 Geo Prizm