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Losing voltage when temps are below freezing.


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On my 2010 DJ base 2.4 176k I have determined that when the outside temperature is below freezing the car will show 11.8 volts or below on my digital 12v socket plug in volt gauge and not start. As soon as I activate the block heater and trickle charger that I have installed under the hood it will start. I am going to rewire all the grounds under the hood as they are grounded to the firewall but not with decent wire gauges. There is a ground on the back exhaust pipe to the pipe hanger that I havent got to yet either, but I put a decent sized ground strap from the negative jump point to the engine. Any suggestions as to what components are affected by temperature that would cause this condition to happen? Havent got to alternator/engine block yet to clean connections, but it puts out 14.6 after it starts. It did go down to 13.6 after I ran it for a few hours. 

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How old is the battery that is showing the low voltage ?  Batteries can get weak in as little as 3 years.

Battery lead acid chemistry causes voltage to drop a lot from room temperature, but yours seems excessive.

 

You  could get battery load tested at one of the auto parts places. Cold cranking amps could be weak just from age.

 

Cleaning up the grounds, especially around strut towers where it gets rusty is always a good idea.

 

 

 

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The battery is 2 years old. I havent got to it to clean it yet. This car came from the west coast and there isnt very much corrosion. I think that the battery is fine and there is something that contracts just a bit when its freezing that doesnt allow the full charge to go into the system.

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Well it is 2 yrs old first i would get it load checked and also have the alt checked to make sure it is producing what it should, (BETTER to know it is good than to think it is good)then i would take the time to remove the cables off the battery and clean then and the post real good and then reattach them tight and then also spray some corrosion spray to the terminals and then go from there,also check the grounds up at the jump terminals  to make sure they are clean and tight also the starter and frame as well. all this is free and just makes good sense take some steps, before chasing other thoughts as to what is happening

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Advance said they couldnt test the alternator but its on the list for spring. I just checked the ground strap on the end of the exhaust to the hanger stud it was completely rusted cleaned it off and put it back on checked the connection. It just clips onto the shafts what a wonky set up. 

 

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So I was watching the voltage of the system on my multimeter and pulling fuses and when I pulled M13 fuse  voltage which was 12.44 went up to 12.56 and going. The designations are IOD-CCN WCM, SIREN, CLK, MOD, MULTIFCN SW. I am thinking now of putting in a cabin mount microswitch that will toggle the circuit off when I park it. No other fuses affected the voltage. Pre-parasitic draw test. And I have the cabin lights set to off on the switch.

 

 

 

 

 

Edited by MartyZ1
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On 3/8/2022 at 11:15 AM, MartyZ1 said:

Advance said they couldnt test the alternator but its on the list for spring. I just checked the ground strap on the end of the exhaust to the hanger stud it was completely rusted cleaned it off and put it back on checked the connection. It just clips onto the shafts what a wonky set up. 

 

any auto parts store can check your alt to see if it is working properly advance auto lied to you or their tester was broke or he didnt know how to use it

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Your alternator seems fine, dropping to 13 when battery charged imo normal.

 

Also cars have a go to sleep type delay of around 2-3 minutes after shut down before the voltage drops to its normal overnight draw.  Digital clock  radio memory etc should only draw around 40-80 milliamps. Key off, drivers door closed.
 

Bluetooth module malfunctioning is the most common thing to cause parasitic draw. Not sure which fuse that is.

Milliamps is more accurate measurement for draw,  not voltage. 

 

 

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Milliamps would be the value if I went as far as disconnecting the positive cable and did the test like that but I had the trickle charger and voltmeter on it and just decided to pull fuses and found the M13. You cant search this forum I wish I had seen that post before. I left that fuse out and the voltage was 12.53 this am. Running the cutoff switch when I get it from Amazon

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