1969 road runner 440

[barf75]

I have to jump battery off to start car. Battery is new and I have tried other batteries. Yesterday I ran the car for about 60 miles on the freeway with no problem. Alternator gauge was pegged. Get back home, cut car off, try to start and no juice in the battery at all. Any ideas?

 

[Zeppelin264]

Need to check resting voltage, and then what the battery is seeing at idle or reved up a little. My guess is your voltage regulator is bad and it's either over charging or not charging at all.

Use a volt meter and check the battery out, that's the best place to start.

 

[aeon280]

Don't rely on the gauge. Get a mutli-meter and start at the alternator with the engine running and check the voltage coming out of the alternator. Should be >14 volts and will increase if the RPM,s increase. If its good move on to the voltage regulator on the firewall . Not sure what the color of the output wire is on your model but its typically blue or green. The voltage from that wire should be 14.4. If both test good then you will need to have a wiring diag for your model as it gets a bit more involved at this point. My experience is on D150,s and the charging system on those routes through the back of the gauge cluster. Not sure of how it works on a Roadrunner. Once you have a diag just keep checking voltage along the path until you find the culprit. Ultimately with the engine running you should be reading around 14 volts at the battery.

 

[Speedbird]

It does sound like your regulator has fried the battery.
You have to "jump off" to start ?
You have "tried" other batteries and it still doesn't start with out a "jump"?
If we work on the assumption you have only one problem, go back to the battery.
BUT the regulatory may have fried you original battery.
"Alternator gauge" doesn't tell if you are talking about an aftermarket volt meter or a factory amp meter.
Is this a mechanical or later electronic regulator?
I assume this isn't an original A12 so the engine has been replaced.
More information when you get it.

 

[SlinktRR]

sounds like a good time to do voltage drop test. May have current going somewhere it should not be, draining the batt. Need a dmm to do some testing.

 

[oldbee]

Dirty batt. posts,bad connections? If ur jumping with batt cables ur effectively going around a bad terminal connection at battery. But all the above posts are relevant too. A dirty batt connection can stop cranking & charging.