[i82much]

Last night I took my car out for the first drive of the season. Started up just fine. Stopped to fill up, and the car wouldn't start - turned the key and nothing. Let it sit for a few minutes and it started up fine.

When I got home, I put a voltage meter on the battery. With the ignition key off, it read about 12.6 volts with the red test lead touching the lead positive battery post. Driver's side door left open and the interior bulb was really dim.

I move the test lead to the nut that holds the terminal onto the positive post, and it reads around 3 volts. Same result (3 volts) at the other end of the positive battery cable where it connects to the Ford-style solenoid.

The battery is seven years old, so I should probably replace it anyway. But I don't get why the lead post would read over 12 volts when it is only 3 volts right at the battery terminal nut and at the solenoid. I guess it could be a corroded terminal, but the terminal looks fine and I can't understand why the car cooling off would make a difference?

Interesting note, this car does have electric fans. So maybe the car cooled off enough to drop below the threshold where the fans turn on, in between when I first tried to start the car at the gas station and a few minutes later and I got it started. But that doesn't explain the difference between the reading at the post vs. the reading at the terminal?

[67gtospud]

Check all your power and ground connections. Make sure they're clean and tight. You can also do a voltage drop test and resistance test on your wires to check the condition of them.

[STEELCITYFIREBIRD]

I’d surmise that terminal is either loose or dirty., or both! You just did a voltage drop test,...and found the drop. The terminal is likely hot..,from the poor connection. And makes better connection when it cools.
My 2 sense!
HTH

[i82much]

The terminal is definitely tight, and I had that red anti-corrosion spray on it. I don't see any corrosion. But who knows, right? I ordered a load tester and I plan to test all my batteries when I get it, the GTO, old truck, tractor, etc. I will clean up the connection really good when I pull the battery and go from there.

[Formulajones]

Battery terminals are funny like that. They do tend to get a film on them over time that is hard to see. Not corrosion but it is enough to affect the connectivity. And they'll seem to act up intermittently.

Just a quick clean up with a terminal cleaner will cure that issue. My bird was doing the same thing last year. Terminals appear fine. I was backing into a spot and with the backup lights on and foot on the brake, my radio went haywire. Let off the brake and it was fine. Turned my lights on and noticed they were dim. I grabbed the battery terminal and although it was tight I tried to move it. Didn't move but the attempt was enough to bring everything back to normal. I got back home and hit the terminals with the wire brush real quick and it's been fine since. No visible corrosion, just an old connection that wanted freshened up.

As far as the batteries age, a load tester will give you an idea on battery health.

[i82much]

why did the car start after it cooled down a bit? I didn't touch that terminal! I'm confused. Thankfully, I'm used to being confused - it's nothing new for me!

[steve25]

Both the no start at the fill station and the dim interior light are from the same root cause of the bad connection at the battery.

The low voltage condition at your ignition was not even enough power to close the solenoid on the starter motor.

[i82much]

Originally Posted by steve25

Both the no start at the fill station and the dim interior light are from the same root cause of the bad connection at the battery.

The low voltage condition at your ignition was not even enough power to close the solenoid on the starter motor.

so maybe just popping the hood let the terminal cool down enough? I guess I can see that, maybe the terminal contracts a bit as it cools and gets a better connection? Weird stuff.

[dataway]

Something I've learned from all my tractors and such .... most electrical problems that show up on the first use after winter storage is going to be related to bad grounds or corroded connections that developed over the winter.

Had a similar problem with one of the tractors ... dang the battery terminals looked clean, but cleaned them anyway, seated them real well before tightening .... problem solved.

[Formulajones]

Yep,,,, There is a name for that film they develop over time that is hard to see but affects the connection. The name of that process escapes me at the moment.

[gene simmons]

Originally Posted by i82much

Last night I took my car out for the first drive of the season. Started up just fine. Stopped to fill up, and the car wouldn't start - turned the key and nothing. Let it sit for a few minutes and it started up fine.

My 66 did that when the starter solenoid would get hot. Do you have a heat shield over it?

[STEELCITYFIREBIRD]

If you lights are dim, nobody has good power!
Easy peasy fix usually...do both.

[West Coast GTO]

Electrolysis, process by which electric current is passed through a substance to effect a chemical change. The chemical change is one in which the substance loses or gains an electron (oxidation or reduction).

Originally Posted by Formulajones

Yep,,,, There is a name for that film they develop over time that is hard to see but affects the connection. The name of that process escapes me at the moment.

[gtofreek]

Just like Formula said, a hard black crust develops between the battery post and the cable end. It will eventually stop a connection as you found out. Just pull the cable end off and look at the inside of the cable end and at the battery post. I bet they have a black crust on them. Scrape it off and it will start fine again. I used to fix starting and charging systems for over 11 years and fixed many starting problems from doing this.

Sometimes just cooling off a bit the connectors shrink enough to make contact again.

[TedRamAirII]

Originally Posted by Formulajones

Yep,,,, There is a name for that film they develop over time that is hard to see but affects the connection. The name of that process escapes me at the moment.

The film is OXIDE/Corrosion. A Nice Clean Shiny Connection is all it needs. I see some people tighten the terminal, like its the only thing holding the car together, it just needs to be snug. Many a terminal has been molested by over tightening.

[Greg Reid]

Your voltmeter told you what the problem was right away. Good voltage at the battery post means battery is good. Low voltage at the terminal nut tells you that the connection between the post and there is bad. Trust your tools.

[FrankieT/A]

Originally Posted by TedRamAirII

The film is OXIDE/Corrosion. A Nice Clean Shiny Connection is all it needs. I see some people tighten the terminal, like its the only thing holding the car together, it just needs to be snug. Many a terminal has been molested by over tightening.

I agree with Ted...A lot of people don't realize the negative and positive posts on top post batteries are different sizes. Your top post clamp needs to be open enough to sit flush on the top (at least) before tightening and the bolt just needs to be snug. Its amazing how many terminal ends are adulterated (or molested as Ted puts it) by over tightening or installed with hammers.

[Old Goat 67]

A REALLY CLEAN connection first, THEN, a really good no-oxide electrolytic grease second, ALL OVER. Not too much so that it will not run everywhere when hot.

Battery connection worry's are OVER. For many years.

[Formulajones]

I don't think anyone was questioning how tight a battery cable should be, not sure where that came from.

It doesn't matter how tight you make it, has nothing to do with the electric film process that I was talking about. That film I was talking about will still form between the post and terminal and kill the connection. I've found that just touching it or even trying to move the cable will temporarily return connection. It did in my case well enough to get the car back home so I could remove the cable and properly clean it.

["QUICK-SILVER"]

I've found those green and red felt pads pretty much useless for stopping oxidation and corrosion.

BUT, If you smear them full of dielectric grease and make sure your cable ends go all the way down and seat in it....It'll pretty much gurantee no corrosion or oxidation coming up from the bottom.

Sprays and what not that keep the top lookin' good, doesn't help what grows from undeneath.

Clay