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no start issue
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=77518		 Page 1 of 1
Author:  mikey1273 [ Sun Nov 24, 2013 4:31 pm ]
Post subject:  no start issue
Last night when it was 25ºF out my jeep failed to start. Was sitting for about 7 hours parked outside.
It tried to crank but just not enouh power to get the job done. So I had to get a ride home. Went back today with my dads 4 banger toyota truck could not get it jump started. The battery is 800 cca advance auto zone gold one year old and altonator is less than 2 months old.

So we removed the battery took it to advance, they charged and tested it declared it was a good battery. They asked me to bring it over when it started to check the alternator.

Put the battery back in, cleaned the battery terminals and it started up ran a few seconds and shut off. It did restart and stay running. Next took it to the store. They checked the alternator said it was fine but claimed something was draining the battery and he could not complete the battery test in the vehicle. I really think he wasn't waiting long enough for the inside lights and other delay items to shut down cus he didn't want to be out in the cold .

my question is are there any known things that can go wrong to cause excess battery drain I can look at ?

For now I have a solar charger plugged in and am going to park over night with a trickle charger and the block heater on
Author:  bugnout [ Sun Nov 24, 2013 4:38 pm ]
Post subject:  Re: no start issue
Lots of things could be causing the drain. Need a multimeter and time to pin it down. Suggest you make sure that all the interior lights are not on.

As a temporary measure, you could install a battery disconnect until you find the problem circuit. That way your battery wont be drawn dawn while its parked.
Author:  jsrmonster [ Sun Nov 24, 2013 5:07 pm ]
Post subject:  Re: no start issue
Hi,
It could be a larger than normal parasitic drain across the diode/triode of the alternator. Get a isolator switch temporarly installed like this.

http://shop.advanceautoparts.com/webapp ... tor+switch

Then place a fluke/ammeter across the lugs of this switch and turn the car off and lock the doors. (make the hood switch closed if it has one) hood still open. You can make the door switches closed in the lock assembly too while keeping drivers door open.

Now with car locked and asleep, switch the isolator off (ammeter still hooked across lugs). and you will see what it's drawing. Should see 50-150ma, but no more. If you can light a 12v light bulb across the lugs, something is drawing current.

You can now check voltage at fuses, and relays and systematically remove active fuses while watching ammeter for changes.

Body control modules and alarm systems that don't go to sleep can kill batteries. Dual battery cars can also have a 2nd bad battery (like touaregs - I have 3 of them). Sometime you can lock your car from the passengers side and close door and vehicle is locked without alarm system constantly polling and drawing current. A bad alternator is just that, and will back-feed too much current thru the diode/triod (easy check is to unplug the 12v lead).

Jeff
Author:  mikey1273 [ Sun Nov 24, 2013 5:28 pm ]
Post subject:  Re: no start issue
I don't have the equipment to try that trick with the switch. but if I gather from what you are saying if I disconnect the alternator led where it bolts from the battery cable that would prove the diode in the alternator is the issue if that battery never gets depleted to the point it cant fire the engine after some time.

It needs said that this is an advanced auto auto alternator I bought to get me by... I still have the original that I believe is only a de-coupler problem.
Author:  Billwill [ Mon Nov 25, 2013 4:05 am ]
Post subject:  Re: no start issue
Yes you can disconnect the thick lead that goes onto the alternator to stop backflow of current due to a shorted diode.

however there are lots of other things that can cause the power to drain....the first thing is to check that the battery is getting a good charge while engine is running. You need to put a meter across the battery terminals...should show about 12.5 volts while engine is off. If the voltage drops to about 9 volts while the engine is turning over then you could have a bad battery.

At idle the meter should show at least 13.5 volts or else the alternator is not charging properly. :(
Author:  Hexus [ Mon Nov 25, 2013 9:22 am ]
Post subject:  Re: no start issue
First things first, replace the $7 ASD relay. That was causing me issues and it being bad will NOT trigger a CEL.

Also scan to ensure you aren't getting a glow plug code, those will eat batteries too.

After that, I would start tracing wires, but specifically those around the engine because they're known to melt or fray pretty quickly at 7+ years old.
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