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Slow cranking in cold weather

1607 Views 6 Replies 4 Participants Last post by  15cruzediesel
So we had a 20 degree F morning a couple weeks ago and my car barely would turn over but it did start. I thought, well time for another battery. The car has had 4 or 5 batteries in it including the one that came in it new. I charged and tested the battery it came back pristine, even at 2 years old. So I checked on a starter as I figured the starter is dragging and is the starter that came on the car new. The cheapest place was the gm dealer I use at work and it was still $170馃く so I decided to do some more thorough investigation. I checked the voltage drop on the positive cable going to the starter and it was losing 1.34 volts! I checked the negative side and it checked normal at just over .3 volts. So I look at the positive cable checked voltage drop on the fuse block that sits on top of the battery all good. Check from the fuse to the starter and still losing over a volt. I looked at the positive connection on the starter and it was a little crusty so I cleaned the connection on the cable and the starter and BAM .33 volts of drop and starts as it should now! Don't forget the simple stuff. I'll also mention the battery in it now is a super start AGM from o reillys and it has done very well so far. Advance batteries wouldn't even make it a year sometimes.
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Now that is how you diag an issue as opposed to just throwing parts at it since a new stater would have fixed it also but would have cost lots more and a perfectly good starter would have become a core.

Now imagine what that voltage drop had been under load.馃

Most excellent.
 

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Discussion Starter · #5 ·
Now that is how you diag an issue as opposed to just throwing parts at it since a new stater would have fixed it also but would have cost lots more and a perfectly good starter would have become a core.

Now imagine what that voltage drop had been under load.馃

Most excellent.
A voltage drop test is done under load. I removed the fuel pump relay while cranking so I could get a good reading and give the meter a second to stabalize. Black lead on the meter on B+ starter post red lead on the + post on battery (or other test point) and that shows you the voltage difference under load. Around .3 volts for a low current circuit and .5 volts on a high amperage circuit is considered normal.
 
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Discussion Starter · #6 ·
You clearly do not work for a GM dealer service department because this would have been 4 hours diagnosis and $1,000 in parts to fix. Good work.
I'm a fleet tech for a large public utility actually.
 
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A voltage drop test is done under load. I removed the fuel pump relay while cranking so I could get a good reading and give the meter a second to stabalize. Black lead on the meter on B+ starter post red lead on the + post on battery (or other test point) and that shows you the voltage difference under load. Around .3 volts for a low current circuit and .5 volts on a high amperage circuit is considered normal.
I wasn't 100% sure if you measured it under load or referenced to battery return.

I was thinking it probably was under load since it was about a 10% loss.
 
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