losing voltage

northern ram · 10-15-2009, 07:14 PM

i have a 2000 tracker 2.0l ihave a good battery,when i start the vehicle 12.9volts, but as it is idling and you put a voltmeter on you can see the voltage dropping slowly until the battery is drained and can not supply the engine so it stalls out i have checked the alternator and it is o.k,if the starter solenoid is shorting out could it drain the battery like a bad alternator would?

CodyJ · 10-15-2009, 08:24 PM

In a way, but here is my method of testing your problem.

Remove the battery cable that goes to the starter (positive) after starting and see if you have same symptoms... otherwise I would take a look at your wiring from the alt to battery to see if its correct. What does the alternator put out?

aquanaut20 · 10-16-2009, 12:51 AM

Quote:

Originally Posted by CodyJ

In a way, but here is my method of testing your problem.

Remove the battery cable that goes to the starter (positive) after starting and see if you have same symptoms... otherwise I would take a look at your wiring from the alt to battery to see if its correct. What does the alternator put out?

STOP!

Do NOT remove the battery cable while the engine is running, that is the quickest way to spike the ECU and cost you extra $$$$. The battery in the circuit is a buffer and without it the alternator will run wild.

Use a good VOM, battery at rest 12.5vdc, engine running 2000rpm charge rate 14.5vdc. If you do not get these readings clean and check all battery and ground connections, shiny and greased.

northern ram · 10-16-2009, 08:01 AM

my battery is 12.5 to start but when i start vehicle it will fall right away to under 12 and then you can continually watch it drop as engine warms up,keep in mind alternator has checked ok.thinking got to be bad wire somewhere but don't know where to start

aquanaut20 · 10-16-2009, 09:27 AM

Quote:

Originally Posted by aquanaut20

Use a good VOM, battery at rest 12.5vdc, engine running 2000rpm charge rate 14.5vdc.

If you do not get these readings clean and check all battery and ground connections, shiny and greased.

Start at the battery posts and work your way out, big cables first. Make good clean grounds to body, frame and engine.

Alternator grounds via its frame and bracket, make sure clean and tight.

How was alternator tested???

northern ram · 10-16-2009, 10:02 AM

brought alternator in and was bench tested at a rebuilder shop

aquanaut20 · 10-16-2009, 10:15 AM

Double posting here and in the older forum will get you confused, I will bow out.

Jerry on the other forum is the Zuki GURU, I am just an old timer with 50yrs general experience behind me.

kick-fix · 10-16-2009, 11:36 AM

aqua is never a JUST. not close. not by a mile.

first try a new or used known to be good battery,
you do know ,right,, that the alternators regulator can in fact stop trying to charge a battery with illegal internal battery resistance (high) < a bad battery. or cables.?

it does that, so it dont blow $3000 worth of electronics to kindom- come.
that is why Aqua says stop. (throw that old 1965 motors repair book in the trash)

this mechanism should not be relied upon to do a open cable test.
if the test fails, you will pay big $$$

we did this back in the pre electronic days,and for sure in generator days.
ive done it weeks on end, as a kid , parking on a hill at home and at work.
battery in garage. saving up to buy one or just waiting to find time.
coast , dump clutch in 2nd, every day. (towel wrapped on Pos. batter lug)

but dont do that.

so first change the battery to one that is good, one that has normal cell resistances.
no sorted cells , no open cells ,no cells with gross sulfating.

then check cables and the 3 top grounds.

cables end to end.
the ground behind the battery
the cable minus most be on the top of the starter bolt and real tight, NO WHERE ELSE.
as aqua says, the alternator case grounds to the brackets.
if they are rusting, the alternator my go dead.

Alt. minus to frame,>>> frame to block>>> block >>>> to minus lug on battery>>. battery minus.

if that path is bad, you have problems.

that is the ground path few thinkabout. but is 1/2 as important.

44years on job, now retired.

northern ram · 10-16-2009, 03:04 PM

grounds have been cleaned and checked ok

CodyJ · 10-16-2009, 04:49 PM

Quote:

Originally Posted by aquanaut20

STOP!

Do NOT remove the battery cable while the engine is running, that is the quickest way to spike the ECU and cost you extra $$$$. The battery in the circuit is a buffer and without it the alternator will run wild.

Use a good VOM, battery at rest 12.5vdc, engine running 2000rpm charge rate 14.5vdc. If you do not get these readings clean and check all battery and ground connections, shiny and greased.

I should of been clearer, but the one to the starter to battery only.

I bet he has a dying battery or alternator, one of these is causing the problem... I think the worse experience I had with a starter was that it would sometimes turn the motor over and start it, or sometimes do nothing and act like it was a dead battery but the battery was fine. It was drawing all the amps in the world, and doing jack.