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Discussion Starter #1
The passenger side battery reads 13.6 volts and 14.7 on the driver side with the car running.Gauge reads a bit less than fourteen. Usually at 14 or a bit more.

Cable to starter is new

Any ideas?
 

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Whistle Pigs Are Cool
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2,460 Posts
Cross over cable between the batteries clean? All battery cable ends clean and tight? All grounds clean and tight?

Have both batteries load tested as well as the alternator.
 

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Whistle Pigs Are Cool
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2,460 Posts
Is the crossover cable hooked up on the passenger side battery?
 

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5,552 Posts
What year is this? My first thought is a bad ground on the passenger side.
 

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Super Moderator Eco-Logistical
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Only one way the two batteries could show different results... On our trucks, Corrosion and bad connections...

Start by pulling the cables off the weaker battery, if stock cables are on it, pull the rubber off the ends, and inspect the wire and the plate. Clean the battery terminals, and inspect the bolts. I like to install a long 3/8" stainless bolt, with a stainless nut, thread the bolt into the battery firmly, but don't crank on it, then use the nut to torque down on the cable connection... Amazing difference in starting power.

If there is no problem on the battery end, check the block end... Remove and clean the block, the cable and the bolts... You'll find the obvious problem.
 

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9,478 Posts
Only one way the two batteries could show different results... On our trucks, Corrosion and bad connections...

Start by pulling the cables off the weaker battery, if stock cables are on it, pull the rubber off the ends, and inspect the wire and the plate. Clean the battery terminals, and inspect the bolts. I like to install a long 3/8" stainless bolt, with a stainless nut, thread the bolt into the battery firmly, but don't crank on it, then use the nut to torque down on the cable connection... Amazing difference in starting power.

If there is no problem on the battery end, check the block end... Remove and clean the block, the cable and the bolts... You'll find the obvious problem.
Just to tag along on vstech's recommendations, take a look at these:

http://www.dieselplace.com/forum/2755252-post5.html

http://www.dieselplace.com/forum/63-gm-diesel-engines/21-6-5l-diesel-engine/163087-grounds-grounds-grounds-importance-good-grounds.html
 

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Solved..The ground for the passenger side battery is shares the bolt with the alternator bracket..I recently replaced the alternator and the reman that they gave me had loose threads on that bolt hole.I tightened it when I installed it but loosened somehiw and now when I try to retighten I cant..Moved the ground to the intake and its perfect again.Now I'm debating if its worth getting the alt replaced by the builder.

FYI put the meter on the positive of the alternator and the other on the neg of the one of the bat first and then the other.

BTW spent a whopping $1.22 at home depot and did the nut/bolt mod..(did the other a while back)
 

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My 6.5 scared a prius
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1,215 Posts
thats what happens with crappy aluminum/magnesium mixed press molded parts such at the alternator casings. if the threads are shot, i would take it back and tell them to replace it and that it was messed when you got it, no sense on relying on a bolt hole that wont hold a bolt. also, on the alternator bolt hole, put some threadloc on it as well to hold with the vibration
 

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My 6.5 scared a prius
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if its under warranty then why, just have it replaced, doing modification can void the warranty
 

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Did you clean the alternator mounting points?



Did you peel & clean the battery terminals?



To find a voltage drop, set your digital multimeter (DMM) to the 20VDC range (disable AUTO range), and probe from one battery's (+) terminal to the other. Try to get the meter probe on the actual BATTERY terminal; not the CABLE terminal, or the bolt (unless you're 100% certain they're totally clean & making perfect contact). It should read less than 0.5VDC (or whatever your meter shows when the probes are touching each other). If it's significantly higher, begin moving ONE probe at a time across ONE electrical connection at a time - for instance: from the battery terminal to the cable terminal; or from the cable terminal to the cable itself (by piercing the insulation with the probe). When you see the voltage reading change, you just moved across a point of high resistance. Pinpoint it by moving the probes closer together, then disassemble, clean, & tighten that joint. Applying ELECTRICAL grease (not DIelectric, thermal, or chassis) will keep the connection clean much longer. Then, START OVER FROM THE BEGINNING.

Once you've done the (+) cables, start over on the (-) terminals, and find/fix any resistance in that circuit. When you're done, the batteries should always show the exact same voltage.

The same technique works along any other electrical conductor (wire/cable/ground) between 2 points.
 

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Discussion Starter #12
I didnt clean the alternator mounting poles..I refuse to clean the alternator mounting poles..
 

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Well, you GO, girl!
 
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