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Old 04-28-2016, 06:50 PM   #1
swatkins
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montana short impossible to find

Dear all,
I recently fixed a blown head gasket and intake gasket. The engine works fine. After a day or two i had problems starting...and the battery was low. I charged it...it fired fine again. Next day battery was low again and it was hard to start. I baught a new battery as the other was 4 years old. Again new battery low after 1 day.

I then followed general tests to find problems. A short was detected by placing a voltmeter inline with first the positive then negative terminal...both showed 10 volts with ignition off. I checked frame and engine as ground and both were 3-4 ohms. With the battery ground removed...there was still the same voltage on the pos n negative. I then went through all the fuses 2x on the negative and once on the posative and nothing broke the current...ie no circuit leak. I checked other engine block ground points and they were fine. Tested alternator and its cranking at 14-14.5 with the battery. The battery holds enough charge for about 6-7 hours after running for 20 min to start. Overnight or all day it is drained enough to prevent starting or will take several tries. No blown fuses, even the starter inline fuses.

I live about 1 hour from any city and have the general tools and a voltmeter. I woundered if anyone had suggestions on battery draining shorts...and might know how to proceed further. . Any help is appriciated. Steve
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Old 04-28-2016, 07:28 PM   #2
brcidd
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Re: montana short impossible to find

First of all- you have a battery drain problem, not a short problem--a short would either blow fuses or create heat and smoke.

I always do the amp draw test, not voltage test. Take all positive cables off battery, set up your DVM (turn knob to dc amps) for DC amps on the 10 amp connector- connect one end of DVM to battery positive, the other to the load cable. Keep doors closed, hood light off etc. Watch the amp draw go down as various components go back to sleep (BCM, light modules etc.) amp draw should read less than 50 milliamp (0.050 amp) like around .025 or so - this is after about 10 minutes and is the minimal draw of ECM etc.

If amp draw is greater than .050 amp after 10 minutes- then pull one fuse at a time (no replacement) until you see it drop-- if you replace fuses, expect components to have to go back to sleep again.

If all is fine, then do amp draw on starter positive lead, and alternator lead- alternator could have an internal short- seen it once- telltale sign is if it is warm after 6 hr sit.....
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Old 04-29-2016, 01:06 PM   #3
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Re: montana short impossible to find

A battery draw means a short, or over drawing from a component like the ignition or starter.... A short doesn't necessarily pop a fuse. Aside, Ill try that as well, however it is at the lower end of measurement on the voltmeter I have, so might not be noticeable. I get 0.025 variation from the car slightly being bumped...
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Old 04-29-2016, 02:05 PM   #4
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Re: montana short impossible to find

Quote:
Originally Posted by brcidd View Post
First of all- you have a battery drain problem, not a short problem--a short would either blow fuses or create heat and smoke.

I always do the amp draw test, not voltage test. Take all positive cables off battery, set up your DVM (turn knob to dc amps) for DC amps on the 10 amp connector- connect one end of DVM to battery positive, the other to the load cable. Keep doors closed, hood light off etc. Watch the amp draw go down as various components go back to sleep (BCM, light modules etc.) amp draw should read less than 50 milliamp (0.050 amp) like around .025 or so - this is after about 10 minutes and is the minimal draw of ECM etc.

If amp draw is greater than .050 amp after 10 minutes- then pull one fuse at a time (no replacement) until you see it drop-- if you replace fuses, expect components to have to go back to sleep again.

If all is fine, then do amp draw on starter positive lead, and alternator lead- alternator could have an internal short- seen it once- telltale sign is if it is warm after 6 hr sit.....
That is about the only way to track a draw. Before I hook up the meter I pull the dome light fuse or figure out a way to override the switch since you might need to get inside to pull fuses.
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Old 04-29-2016, 02:37 PM   #5
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Re: montana short impossible to find

So, I performed the amp draw test as suggested. The results

theres a 200 ma draw

Bat main fuse 60 amp (in hood) stops draw 100%

50% reduction to 100 mamp
Ign main fuse (in hood)
....inside car fuses
cruise control fuse
cluster battery
ignition 1
PCM/ABS

If I remove the cruise control fuse, the Ignition 1 and PCM/ABS no longer have an effect on draw, but there is still a 100 mamp draw...

I will now go through wiring, but am still open to any suggestions.

Steve
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