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Discussion Starter #1
Hello everyone - love the site!

Well here is the deal. Wife has a 02 PT with auto trans and
 

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Put a voltmeter across the battery with engine running, and immediately after shutting it off, and one hour after shutting it off. Let us know what numbers you get.

Also, check fault codes: http://www.allpar.com/fix/codes/index.html
 

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There could be hard crust and scale on the inside contact surface of the battery terminals. If it is bad enough, it can actually cause 'no connection'.
By jumping the battery on the outside of the battery terminals, you are bypassing the bad connection.
 

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Agree with both posts above. I'd check and clean the battery posts and cables. If the no start condition and odd electrical conditions still exist (random dash lights) it points to a weak battery or insufficient charging system. As suggested, measure the voltage with the engine not running - should be a minimum of 12.8 volts and over 14 volts with the engine running. If it's less than 14 volts (engine idling) the alternator is bad (brushes worn or a bad diode).

Just went through this with my son's Mercury. Measured 12.4 volts at rest. Was getting intermittent no starts. With the engine at idle the voltage still only measured 12.4 volts so I knew the alternator was kaput - I'm guessing his had a bad or shorted out diode. Installed new alternator and the battery measured 12.6 volts at rest (just enough to start) and 14.5 volts initially and eventually dropped to a more normal 14.15 volts with the engine at idle.
 

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There could be hard crust and scale on the inside contact surface of the battery terminals. If it is bad enough, it can actually cause 'no connection'.
By jumping the battery on the outside of the battery terminals, you are bypassing the bad connection.
Thanks, good point. I forgot the most obvious, and this happened to me once.
 

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You need to also take a close look at your battery cables. If there's any corrosion on them, odds are that there's also corrosion under the insulation. You could strip back about a 1/2" area and check it. If so, replace both the positive and ground cables. No point in doing a half-arsed job.
 

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I've even had corrosion occur between the cable copper strands and the battery terminal! Cleaned and shined everything but the test light revealed a bad link.

By using felt washers under the battery terminals and saturating everything with corrosion inhibitor my little '95 spirit's OEM battery terminals are like new. Bare terminals are asking for trouble.
 

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+1 (well 2, i guess) on the bad connection at the battery. My Spirit did this and my best friend's girlfriend's truck did this-- both times, the cables were loose and the terminals were badly in need of cleaning. Often, they can move just enough when jumping to make a good enough contact, and then shift back to the bad spots while driving.
 
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