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Battery / ALT / Need Understanding

brian72

Early Bronco Student
Joined
Jun 18, 2001
Messages
4,157
I have a yellow optima - I got my starter and alt from rrraaayyyy22

I have not driven it for a couple weeks and it was hard to start. Needed a jump. Drove it for a while and the next day it was hard to start but it did. It ran for about 30 min and then sat for 2 more days...needed another jump. Did some searching and found other similar battery, charging issues; so I took some measurements.

  • Before trying to crank - 12.8
  • tried cranking and basically dead sounding - the voltmeter was now going up to 14.29
  • Went to have dinner
  • After dinner the reading was 12.76
  • During cranking I was seeing the voltmeter in the 3.0-4.0 range
  • Jumped the truck
  • Running with light on - 14.45
  • Running w/o lights - 16-17
  • turned truck off - holding steady at 15.23
  • measure 2 hours later - 13.8

Took the neg cable off - hooked up test light to cable then touched light to neg battery post and the light did not light up....that would test for drain right?

anything else to check and measure....What does the above tell us?
How to measure if alt is good?
 
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RRRAAAYYY2

Bronco Guru
Joined
Nov 10, 2004
Messages
1,684
Loc.
Brantford, Ontario
Something is messed up. Do you have a different battery you can try in the system. i.e. take the Optima out and try using another battery you know is good.

It looks like the battery is bad, so I would confirm it first, then we can check the alternator afterwards. (Other possiblity is it has a bad regulator or sense wire). But the battery should not drop below 11volts, maybe 10.5volts well cranking.
 

sbolejack

Sr. Member
Joined
May 3, 2006
Messages
357
Loc.
Rogers, AR
Sorry to hear someone else is having charging issues! I hate electrical problems with a passion.:mad:

I have changed battery, alt and regulator and still have issues. Going to tear the wiring apart and start tracing everything.

RRRAAAYYY2 - tried to call you this weekend to discuss options. Is it better to call you during the week or on the weekend?
 

jghflys

Jr. Member
Joined
Mar 15, 2007
Messages
117
Loc.
Texas
Running without a load at 16 to 17 volts across the battery is too high and will damage the battery. 13.5 to 14.8 volts at the battery with the engine running is good. From the voltages, it looks like the regulator is over charging the battery and may have damaged it. I would change the regulator.

James
 
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brian72

brian72

Early Bronco Student
Joined
Jun 18, 2001
Messages
4,157
Something is messed up. Do you have a different battery you can try in the system. i.e. take the Optima out and try using another battery you know is good.

It looks like the battery is bad, so I would confirm it first, then we can check the alternator afterwards. (Other possiblity is it has a bad regulator or sense wire). But the battery should not drop below 11volts, maybe 10.5volts well cranking.

Ray - this was done with the black voltmeter wire on the neg battery post and the red voltmeter wire on the pos past post..Correct procedure?

another thing...when cranking the solenoid is clacking...is that because of not enough juice? I replaced with new one and same issue.
 

RRRAAAYYY2

Bronco Guru
Joined
Nov 10, 2004
Messages
1,684
Loc.
Brantford, Ontario
The solenoid clacking is a sign of not enough voltage, or bad ground. Do a voltage drop test on everything http://www.svapowerproducts.com/html/voltage_drop.html

If you have 12.8 in the battery, you should not have voltage drops that cause the solenoid to clack, or the battery to drop to 4volts. I am leaning towards a broken inner plate connector in the battery, only thing that would cover all your symptoms. Pretty common issue with the battery as well. But it could still be something else, so dont just buy another battery, test things first.

Also check the yellow wire to make sure it is reading 100% exact same as the battery voltage. Common problem on OE applications that cause it to over charge.
 

RRRAAAYYY2

Bronco Guru
Joined
Nov 10, 2004
Messages
1,684
Loc.
Brantford, Ontario
Sorry to hear someone else is having charging issues! I hate electrical problems with a passion.:mad:

I have changed battery, alt and regulator and still have issues. Going to tear the wiring apart and start tracing everything.

RRRAAAYYY2 - tried to call you this weekend to discuss options. Is it better to call you during the week or on the weekend?
Anytime should work, i have the Tech line attached to my cell phone too. It is turned off from 11pm to 7am EST, and Sunday mornings.
 
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brian72

brian72

Early Bronco Student
Joined
Jun 18, 2001
Messages
4,157
The solenoid clacking is a sign of not enough voltage, or bad ground. Do a voltage drop test on everything http://www.svapowerproducts.com/html/voltage_drop.html

Also check the yellow wire to make sure it is reading 100% exact same as the battery voltage. Common problem on OE applications that cause it to over charge.

Did the voltaqe drop test..
positive post - .02
neg post - .01

What yellow wire are you referring to?
 

RRRAAAYYY2

Bronco Guru
Joined
Nov 10, 2004
Messages
1,684
Loc.
Brantford, Ontario
Is it not a 3G alternator? The yellow wire is the one going into the regulator that attaches to the positive output post of the alternator.

Or do you have one of the GM one wire alternators? i.e. no wires attached to the alternator.

Your voltage drop test, this was while cranking? Go from positive post on the battery to the "S" post on the solenoid and test that complete circuit. If it is still clanking and the drop is only .2, then I would say almost 100% sure it is a battery.
 
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brian72

brian72

Early Bronco Student
Joined
Jun 18, 2001
Messages
4,157
Is it not a 3G alternator? The yellow wire is the one going into the regulator that attaches to the positive output post of the alternator.

Or do you have one of the GM one wire alternators? i.e. no wires attached to the alternator.

It is an ALT I got from you with my starter...It has one wire coming from the alt going to the post (when looking at the solenoid) on the right.
 
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brian72

brian72

Early Bronco Student
Joined
Jun 18, 2001
Messages
4,157
did the voltage drop test again.
While trying to crank :
-neg lead on neg battery post and post lead on post battery post it show 12.8 but try and crank and it then shows 3-5 v

-neg lead on the solenoid wire from the alt and the post lead on the stub at back of alt - while trying to crank it shows 15-16

must be the battery.
 

RRRAAAYYY2

Bronco Guru
Joined
Nov 10, 2004
Messages
1,684
Loc.
Brantford, Ontario
Sorry I missed this. I would say 100% battery is bad, I dont think even a dead shorted starter could drag a battery that low that quickly. I would try a different battery out of a good car, just to make sure.
 
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brian72

brian72

Early Bronco Student
Joined
Jun 18, 2001
Messages
4,157
yep - forgot to update.
Tried different battery and it cranked without issue.
Took battery to parts house to test...within 60 sec it came back bad
 
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