tighe

Battery cable clamps -cause of no start?

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Small update. Yesterday I installed the negative cable from FCP, cleaned the terminal posts, and It started no problem. 

but, it had been starting no problem for the past week or so, so nothing conclusive there. The non starting an intermittent thing, so it’s been difficult to pin down. It’s can always be corrected by loosening the cable clamps and moving them around on the posts a bit. 
 

Today I went to fire it up and no start. Ugh. Moved the positive clamp around and it started. When I get a little more time I’ll be replacing that one as well. 
 

it’s worth noting that even when the car doesn’t start, there is still power- the lights and radio etc all work, but nothing other than a single click when I turn the key further. 
 

Will report back once the positive cable is installed. 

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On 2/10/2020 at 6:18 PM, tighe said:

I was looking through some of my notes today and sure enough, when describing this issue to a mechanic friend of mine I described how the positive battery terminal got very hot after driving. Guess I forgot about that... 

Not sure what to conclude from this, but figured I'd get it written down here for posterity. 

Conclude that there is corrosion inside the cable, where it connects to the lug. That's why I suggested you check it.

The corrosion causes the resistance to go up, which causes amps going through to go down and the wire to get hotter, which causes the resistance to go up more, etc. So when it's been driven for a while it can't pass enough amps for the starter (V = IR). 

The problem is the positive cable at the battery lug. Go ahead and install the POS, non-OEM part from FCP, it will be better than the corroded original one in there. That will fix it. 

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Awesome, thanks for the great explanation! Makes a lot of sense. I’ll get to replacing the positive...I’ll make it a priority now.

Really appreciate the explanation.  

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