Hot Rods Battery or not?

Hey Gentlemen, I have a problem. I started my Merc. drove it to Sonic, when I was ready to leave the car would not start. Had the Wife come jump the battery and the car started right up. Had the Battery tested shows good, and no dead cells. Alternator rebuild two years ago. Anybody have any ideas????? Thanks

 

Loose connection, bad ground, corrosion some where on a termination point. All could cause a high resistance problem.
Check all your battery connections both at the battery and the starter and where you ground on the block or frame.

 

Check the alternator output and do a starter draw test. If the starter is drawing too many amps it can run a battery down very quickly. The alternator may not be putting out enough amps to keep the battery charged. Joe

 

I would test the alternator next.

 

Thanks for the help.

 

I have never had much luck with getting a battery tested at the auto parts house. A battery can test well but still not pull the amps necessary to start your car. I think that they don't test them under load, and to test the amperage it is putting out it needs to be under load.

 

Yup. The only way I have seen a battery tested accurately was when I could use an old Sun Vat 40 tester. It could show you how the battery is under load when cranking.

 

I use an amp meter with the battery in the car and someone cranking it. It has always worked for me.

But if someone still has Sun testing equipment they is about as good as it gets.

 

Wish I still had mine. It was stolen from the Chevy dealer I worked at years ago. Along with mine and 5 other guys tool boxes.

 

I had same problem on SBC. Turned out to the ground from frame to block.

 

Had a similar issue recently, would start with the charger connected, voltmeter showed charge. Unhook charger, no charge. shut it off__& no start. Found the battery post clamp was cracked. R & R'd clamp, back in business.

 

Like donno above says, we see a lot of that in our shop. Probably replace 2 or three battery post clamps a month. Several customers have come in to report their late model cars are "haunted" - the power door locks operate at random, same for power windows, instrument gauges perform impromptu light shows, etc. Almost invariably we trace the issues back to a bad ground connection, often at the battery. Apparently the low voltage electronic circuits are highly sensitive to grounding. Hope you get your Merc healed soon for cruising season.

 

Go to Sonic... leave the wife home. That's what you get.

Bad spot on the starter maybe? Agree on checking all cables, connections and cleaning them up.

 

Another thing to try if this happens: Turn on headlights. If they are bright, it is not Bat voltage. Problem is in activation of starter or solenoid.

 

Lot of conclusions already posted, with some key information missing. Did the starter crank over the motor and it didn't start, or did the starter do nothing at all? Any clicks of chattering?