My truck would not start on 2 consecutive mornings this week. It was in the middle 50’s. Later in the day it would start fine. I also noticed a sulfur smell when stopped. I noticed some fluid on top of the pass side battery and cleaned it off. Took it to batteries plus to have them check the batteries and both were fine as far as their machine said. Then another guy took a look and popped of the caps, the pass side water is down below the elements. He said the batteries need to be replaced, but said they may last until winter. Then later today the pass side began to boil again.

The batteries say maintenance free; however the guy at the store said the water should be checked monthly. Is the water boiling because it is low? Can I just top it off with distilled water and be good or should I get new batteries asap? Trying to head out for the weekend with the camper, but don’t want to do something that may cause more damage. Thanks.

 

I think your battery is being overcharged, hence the heat and boiling, could be low water, if thats the case then distilled water will work.

 

I just added some distilled water. Didn't measure it precisely but it appeared to be 30-40 ounces. It seemed like a lot.

 

did you add to the bottom of the holes, or until it over flowed

 

Above the cores(whatever they're called) there was a separate lead bar which is below the holes maybe an inch. I filled it to that, about an inch below the top of the hole.

 

I suspect you have a partly shorted cell in the passenger side battery, causing the other cells in that battery to overcharge.

You could monkey with it, but I would guess just replacing both of them now would save quite a bit of frustration.

 

Get new ones, you may nurse them along for a little while but you will always cross your fingers when you turn the key. Will save you from being stranded most likley.

 

+1!!!!!

 

Get your DVOM.... hook black to L batt - terminal. with red lead check the alt output volts at the alt. Now check it at the R batt + terminal. Now check it at the L batt + terminal. You shouldn't see much of any voltage drop. IF you do see a substantial drop....and I suspect you will. CLEAN all your battery terminals. I suspect the ECM is seeing a much lower voltage than the alt is actually putting out. Charge system is a loop. ECM monitors voltage via the harness at the L batt. IF you have any corrosion or poor connection between the alt and the L side B+ harness this can cause the R batt to overcharge.

I'm also not a fan of how they attached the alt output to the right batt using an eyelet. That's often a point of corrosion and can cause some headaches. On a few trucks I've removed that wire at the R batt, cut off the eyelet and spliced into the B+ crosscable, and soldered the alt output wire into the crosscable. Good coating of liquid black tape to keep any moisture out and you're good to go.

 

there is a battery temp sensor under the drivers side battery when it stops working the batterys get over charged usualy boiling the pasenger side. it took me quite a while to figur that out.

 

Think we had this conversation on another post. Please explain how the batt temp sensor going bad causes the RIGHT battery to overcharge.

 

Mine did the same thing. Pass battery boiled over turned out the drivers side was junk and causing the alt to boil the other. Replace them both and be done with it.

 

Last time I tried to exlplain this I was a little toasty. The voltage regulator is controlled by the battery temp sensor. It charges hard at first and when the batteries heat up it slows down. Why the passenger side gets boiled Im not sure, but I think it because its closer to the alternator.

 

Batt temp is an input, but in the end the ECM monitors and determines charge rate. I'm betting that when your batt temp sensor was replaced it was actually the removal of the battery (since the cables had to be removed) that "cured" your issue. Same with what "faulkner" posted blaming a "bad left battery" for the overcharging of the right bat. IF all things are clean and right you will not see much of a voltage drop all the way from the back of the alt with a dvom to monitoring the charging voltage on the Star Scan. When thing are "bad" I've seen 11 volts on the scan and as high as 16 at the alt.....all due to poor connections which in nearly all cases have been due to corrosion from lack of care......and that one time where the guy left the cross cable unhooked at the L battery terminal. Gotta give his credit though.....he WAS trying to clean his terminals good.

...which brings up an easy way to prove this theory to yourself. UNHOOK the crosscable at the drivers (L) battery terminal (and don't let it ground out!!) and start your truck up. Check voltage at the alt output stud, the R batt + post and then the L batt + post and compare it to the gauge in your truck. Let it run long enough and you'll prove to yourself that you can kill a good battery with.........a good battery!

 

I had two brand new optima red tops, it happend about a week after I installed them. I thought it was a bad connection too, I cleaned them several times I even swaped sides. Finally after all else fails read the directions so I looked it up in the factory service manual and thats what I found. I didnt quote it word for word just the basice idea. I replaced the sensor and am still running the same batterys two years later.