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05-05-2014, 11:56 AM
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#1
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Montana Master
Join Date: Jan 2006
Location: South
Posts: 2,499
M.O.C. #5140
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Diesel and batteries
I have a 2007 GMC diesel. Recently, it wouldn't hold a charge so Kat took it to Walmart to have the batteries checked.
Tech said one was bad and we had it replaced.
After sitting for the weekend, no juice at all. Not even enough to unlock the doors with the remote.
Do both truck batteries need to be replaced if one is bad?
How would I go about looking for a phantom load?
Thx,
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05-05-2014, 12:17 PM
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#2
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Montana Master
Join Date: Mar 2012
Location: Redding
Posts: 1,421
M.O.C. #12339
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I was told it was necessary to replace them both. That said, someone may no more than I do on the subject !
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05-05-2014, 12:47 PM
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#3
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Montana Master
Join Date: Nov 2002
Location: Bakersfield
Posts: 5,316
M.O.C. #15
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Michael & Kat,
I always replace both batteries when one goes bad. Also have the alternator checked. We've had to replace two of them. Good luck. Dennis
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05-05-2014, 01:02 PM
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#4
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Montana Master
Join Date: Jan 2005
Location: North Ridgeville
Posts: 20,229
M.O.C. #2839
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On our 2008 Ford Diesel. It would not start. One battery was about dead and the other weak. Ford said both should be replaced at the same time.
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05-05-2014, 01:14 PM
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#5
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Montana Master
Join Date: Jan 2013
Location: Bridgewater
Posts: 1,196
M.O.C. #13166
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If the voltage drops when you start it up, it's probably your alternator. It could be the new battery was drained on the drive home with no charge coming from the alternator. Also, check to be sure the connections are tight. Seems odd that you have nothing at all.
__________________
2010 Montana 3455SA, Mor/Ryde pin, wet bolts, TST 507, Progressive HW50C, GY G614
2019 Silverado D/A 3500HD LTZ DRW CC
B&W Companion
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05-05-2014, 01:16 PM
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#6
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Montana Master
Join Date: Jul 2009
Location: Olympia
Posts: 1,056
M.O.C. #9441
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I replaced both when I did mine. Mine were not acting up but they were 6 years old so I put in 2 Optima red tops to be safe as I do not like to be in the broke down mode....
__________________
2020 Ram 3500, 2022 Luxe 38GFB,2500w Solar with Victron equipment, Gen Y Pinbox
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05-05-2014, 01:30 PM
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#7
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Montana Master
Join Date: Oct 2012
Location: Chilliwack
Posts: 1,520
M.O.C. #12935
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There is always some drain on the batteries keeping things like the clock and computer powered up. It is best to change both batteries at the same time. I don't know how Walmart determined one was bad and not the other but if it was with a voltmeter then that is a very poor way of testing.
I would disconnect both batteries and charge them with a charger, after you remove the charge let them sit for an hour and then check the voltage and if possible allow them to sit overnight and check both again in the morning. If they are both still up to par then there must be some drain that is abnormal.
If you can start the truck, the voltage at the batteries whether good or bad should read close to 14V that would indicate the alternator is working, if there is no increase in voltage with the truck running then the alternator is likely the problem, however it would have nothing to do with the discharge over the weekend.
Best thing, change the other battery, put a charger on them overnight and then check them after they have sat for a while. They should both read in the neighborhood of 12.8V to just over 13V.
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05-05-2014, 01:40 PM
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#8
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Montana Master
Join Date: Jan 2006
Location: South
Posts: 2,499
M.O.C. #5140
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Thanks for all the replies. Off to get another battery.
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05-05-2014, 02:08 PM
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#9
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Montana Master
Join Date: Mar 2012
Location: Davison
Posts: 786
M.O.C. #12331
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Normally, I would not come to the defense of WalMart, but it is likely they checked your batteries with an electronic tester. In my experience they are not always reliable. A good old fashioned carbon pile tester works best. Electronic testers do not actually place a load on the battery. With a carbon pile tester you can place an actual load on it. I've seen many times when the tester at work would "pass" a battery when I knew in my gut it was bad. Sometimes testing multiple times would reveal it, others not. As for both at the same time, good practice, but not necessary. I was short on cash when mine seemed to crank slow. Checked both with my "old" tester at home. One good and one bad. 15 months later, still running that way. You don't say if they are original. If so, you did well with them.
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05-05-2014, 03:08 PM
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#10
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Montana Fan
Join Date: Feb 2006
Location: Crossville
Posts: 295
M.O.C. #5424
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Yes, replace them both. If not, the old, weaker battery will drag the new one down with it.
__________________
Ted & Beth Uhler, Crossville, TN
and "Monty", our traveling/camping cat
2022 Montana 3781, 2020 Chevrolet Silverado 3500HD
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05-05-2014, 04:09 PM
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#11
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Montana Master
Join Date: Aug 2006
Location: merced
Posts: 983
M.O.C. #6171
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I have a load tester that you can check to see if the batteies are good or bad. Just the voltage test is not good enough. A good load tester can realy put a good load on a batery to tell you what is good or bad.
And after a couple of repeated test, I don't change both batteries if they don't indicate the need.
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05-06-2014, 02:11 AM
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#12
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Montana Master
Join Date: Feb 2012
Location: Lake Gaston
Posts: 8,773
M.O.C. #12156
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If one fails for age, the other is probably going to go as well. But, with my old 2005 Ford Diesel, I accidently shorted out one battery (because you had to take a cover off to check and I screwed up), in the first year. I replaced only the battery I shorted out, and all was well for the next three plus years.
__________________
Mike and Lorraine
2002 3655 FL, 2005 3650RK
2010 3665RE, 2015 3910FB
F350 crew cab dually 6.7
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05-06-2014, 04:45 AM
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#13
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Seasoned Camper
Join Date: Mar 2014
Location: Roseville
Posts: 98
M.O.C. #14137
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Anytime you have a suspected bad battery make sure the shop has a tester that actually puts a load on the battery, that is the only sure way to test a battery. Voltage, hydrometer etc can only give an indication of status. Never, never replace a battery without checking the alternator, low output can decrease the life of the next battery.
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05-06-2014, 05:57 AM
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#14
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Montana Master
Join Date: Aug 2007
Location: Waterford
Posts: 3,693
M.O.C. #7500
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The logic behind replacing both is simple. In a two battery system, the stronger battery doesn't raise the weaker up to it's level. Instead, the weaker one drags the stronger one down to it's level. While a 7 year old battery might check out OK on a non-load test device, that doesn't mean it will check out good when putting a large load on it - like starting. So putting in a fresh battery with a 7 old one results in almost having two seven year old batteries instead one new and one old. I say almost because for a while, the fresh battery will make up for the deficiency of the older battery, but not for long.
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05-06-2014, 12:07 PM
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#15
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Montana Master
Join Date: Jan 2006
Location: South
Posts: 2,499
M.O.C. #5140
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I purchased an identical one and am glad that I did. The first new one was stripped where the negative attaches. It looked good, but I decided to check - it was just snugged up. Evidently after the tech stripped it and didn't have another battery (the lead had stripped), he just snugged it up. Will get another new one tomorrow and replace the older battery.
Voltage is 14 volts per gauge on dash.
Thx for all the help!
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05-06-2014, 01:11 PM
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#16
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Montana Master
Join Date: Aug 2007
Location: Waterford
Posts: 3,693
M.O.C. #7500
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Quote:
quote:Originally posted by snfexpress
I purchased an identical one and am glad that I did. The first new one was stripped where the negative attaches. It looked good, but I decided to check - it was just snugged up. Evidently after the tech stripped it and didn't have another battery (the lead had stripped), he just snugged it up. Will get another new one tomorrow and replace the older battery.
Voltage is 14 volts per gauge on dash.
Thx for all the help!
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Some people shouldn't be allowed near wrenches!
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05-07-2014, 03:00 AM
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#17
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Montana Master
Join Date: Jan 2005
Location: Goshen
Posts: 1,058
M.O.C. #2827
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My previous '05 Silverado had the originals in until Feb of 2013. I went to Sears and had both replaced with 2 of the highest amperage cold cranking power I could get. Found out real quick that the old batteries where just getting old. Because, when I put the new ones in and went to start it up in the cold, they would really crank that diesel over! Mmmm......the guy that just bought it from McCormick's got a good deal!
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05-21-2014, 12:24 PM
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#18
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Montana Fan
Join Date: Jun 2010
Location: Billings
Posts: 155
M.O.C. #10477
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Only one thing to say---------Walmart? Mechanics? they really don't go together.
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