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Unread 08-23-2011, 05:45 AM   #1
ikircher
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1995 YJ Wrangler 
 
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Too much amperage?

hello once again everyone! First, The title should read "too much voltage" lol... I recently had to clean up my battery terminals in order to get my jeep (95 wrangler, 2.5 liter, 5speed). Normally when I start and drive the jeep the battery volts are right at 14 on the gauge. Today the gauge was reading a little higher. The needle was at the last line before the red zone. When does too many volts cause a problem? I had my battery, alternator, and starter all tested and they came back fine. Could this be because maybe there is some more crud on the cables/terminals? or maybe a short somewhere? I figured if there was a short from the alternator my battery would be dead overnight but I don't really know. Any help would be much appreciated!! Thanks in advance!


Last edited by ikircher; 08-23-2011 at 06:05 AM..
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Unread 08-23-2011, 06:07 AM   #2
tdewit
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Quote:
Today the gauge was reading a little higher. The needle was at the last line before the red zone.
Rather then believing the gauge, I would actually measure the voltage at the terminals.

Quote:
When does too many volts cause a problem?
Interesting question. Items like your radio normally have a bit of a working range, from 9 to 17VDC, light bulbs have a wider span of acceptance to voltage fluctuation.

Quote:
Could this be because maybe there is some more crud on the cables/terminals? or maybe a short somewhere?
Look at the basic ohms law equation, V=IR. Crud = R (high resistance) Short = R (low resistance). If you have a short, you'll blow a fuse.

Quote:
I figured if there was a short from the alternator my battery would be dead overnight but I don't really know.
The only thing I would look at is the alternator, seems to be overcharging.
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Unread 08-23-2011, 06:18 AM   #3
oldtime_ironman
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Mine was reading high until I did the gauge-cleaning trick:
http://www.jeepforum.com/forum/f12/r...ter-how-991307
Now the gauge matches the DMM right at 13.8 volts. This is ideal.

Too many volts starts to cause problems when you get up over 14 volts. With 14.2 volts, the battery will overcharge and boil, most likely ruining the battery. As the voltage goes higher, more and more things will start to fry out. A shorted-out voltage regulator will "full-field" the alternator, which can often put out 19 or 20 volts. At that point things just go up in smoke and you would be looking at replacing most of the wiring.
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Unread 08-23-2011, 07:11 AM   #4
Que89YJ
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Important! Stop driving it immeadiately! In an over charging condition(Full Field) you are dumping way more power into the battery then it can take and there is a high risk of the battery cracking and exploding! This is not anything to play with!

Verify the guage with a meter and post back. If it is overcharging then park it until you can fix the issue.
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Unread 08-23-2011, 09:40 AM   #5
ikircher
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ok thanks guys. I will check the volts when I get a break from work...Probably in like 4 hours. Excuse me if this sounds like common sense but in order to get an accurate reading, I need to have the jeep running to test the volts correct?
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Unread 08-23-2011, 09:43 AM   #6
Que89YJ
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Yes, you should test both.
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Unread 08-23-2011, 02:31 PM   #7
ikircher
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I just tested the battery with the jeep off and it read 13.8. With the jeep on the battery read 14.0. If I revved the engine it read 14.1 for a split second then back down to 14.0... I am thinking it must be my gauge in the jeep. It read below 14 when idling and then it was up around the line right before the redline when I would accelerate... Does everything sound right?
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Unread 08-23-2011, 02:37 PM   #8
Que89YJ
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Yes you are fine. There is an adjustment for the voltage gauge. I will post it tomorrow
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Unread 08-23-2011, 02:43 PM   #9
ikircher
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Quote:
Originally Posted by Que89YJ View Post
Yes you are fine. There is an adjustment for the voltage gauge. I will post it tomorrow
Ok awesome.. Thank you so much Que
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Unread 08-23-2011, 02:45 PM   #10
tdewit
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How to adjust the voltage gauge
http://www.jeepforum.com/forum/f12/r...er-how-991307/
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Unread 08-23-2011, 11:24 PM   #11
5-90
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Quote:
Originally Posted by ikircher View Post
ok thanks guys. I will check the volts when I get a break from work...Probably in like 4 hours. Excuse me if this sounds like common sense but in order to get an accurate reading, I need to have the jeep running to test the volts correct?
Test the "battery resting voltage" - engine off, accessories off, read across the battery terminals. Nominal is 12.6VDC, acceptable is 12.0-12.8VDC (anything over 12.8VDC tends to be a "surface charge," and isn't useful for automotive purposes.)

Test voltage again, putting the positive probe on the B+ stud on the back of the alternator. Should be 0.02VDC less than at the battery terminals - or higher. But, it shouldn't be any higher than battery resting voltage (the alternator B+ post is always connected directly to B+ via a fuse or fusible link.) A large drop between the battery + post and the alternator B+ post is indicative of a faulty connexion somewhere.

The running system voltage (basic test: engine running, accessories off) at the battery terminals should be sufficient - if the prior two voltage tests came out OK. System charging voltage should be 0.5VDC higher than resting voltage - at least. Nominal is 13.4VDC, with acceptable being 13.0-14.0VDC. (oldtime_ironman is entirely correct - above 14.0VDC, you start overcharging the battery. Above 14.2VDC, you're boiling the battery! The higher the voltage is, the faster the battery will be wrecked (boiling the top 1/2" or so of plates clear will pretty well wreck the battery totally...)
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Unread 08-24-2011, 05:50 AM   #12
ikircher
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Quote:
Originally Posted by 5-90 View Post
Test the "battery resting voltage" - engine off, accessories off, read across the battery terminals. Nominal is 12.6VDC, acceptable is 12.0-12.8VDC (anything over 12.8VDC tends to be a "surface charge," and isn't useful for automotive purposes.)

Test voltage again, putting the positive probe on the B+ stud on the back of the alternator. Should be 0.02VDC less than at the battery terminals - or higher. But, it shouldn't be any higher than battery resting voltage (the alternator B+ post is always connected directly to B+ via a fuse or fusible link.) A large drop between the battery + post and the alternator B+ post is indicative of a faulty connexion somewhere.

The running system voltage (basic test: engine running, accessories off) at the battery terminals should be sufficient - if the prior two voltage tests came out OK. System charging voltage should be 0.5VDC higher than resting voltage - at least. Nominal is 13.4VDC, with acceptable being 13.0-14.0VDC. (oldtime_ironman is entirely correct - above 14.0VDC, you start overcharging the battery. Above 14.2VDC, you're boiling the battery! The higher the voltage is, the faster the battery will be wrecked (boiling the top 1/2" or so of plates clear will pretty well wreck the battery totally...)
Ok I will try that too when I get home tonight around 7pm eastern time. I drove the jeep today and everything went smoothly. The gauge on the jeep still reads a little higher abover the 14 mark. After I test what you said then that will guarantee that the gauge is screwed up if everything comes back ok. Thank yoU!!
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Unread 08-24-2011, 06:27 AM   #13
Que89YJ
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The alternator output is PWM for the OBDI and will vary depending on load. I agree with everything you said except the 14 volts. Most of the modern cars run at 14.5 Vdc from the alternator. Boiling off the battery is a result of full fielding the alternator. The output from the alternator becomes unregulated and will put out 16-18Vdc at as much current as it can crank out. The exposed plates are nothing compared to the Hydrogen sulfied you produce. It is nasty smelling like rotten eggs and very explosive.

Read the voltage at the battery and tune the guage to the battery. As long as you are around 14.5 Vdc you are fine.
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Unread 08-24-2011, 07:45 AM   #14
ikircher
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again thank you guys so much. This is easily the most helpful forum I have ever been part of and joined. Thank you!!
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