i have a 1966 v8 mustang. i was having a problem with starting. i had to jump it everytime i wanted to drive it. i first realized that the voltage at idle was 10-11v. when i would rev it up it would peak at 17.5v. so the first thing i did was put a new voltage regulator in since it is dirt cheap and i figured that would bring the voltage up at idle and lower it when i rev it. i know the battery is bad so im going to replace it tomorrow.

my question is how do i go about diagnosing the 17.5 volts problem?
where can i find a wiring diagram for it?

 

Well.....we need to know whether the engine is stock or not. I honestly have no idea about the 66s. I'm more of a 80s guy myself when it comes to older models. But yeah, that would help a lot. I have a feeling the voltage regulator might be related to the high voltage problem, so put that in first and then recheck it.

 

Bone stock. the new voltage regulator brought up the charging voltage at idle from 10 to 13 but it still peaks at 17

 

Im thinking it lies with the battery now, the charging system is trying to recharge a bad battery and apparently its working its *** of trying to do it. It may be time to rebuild the alternator to :/

 

new battery and voltage regulator it still charges at 17 volts

 

Are you using a volt-meter or a voltage gauge in your dash to determine what the voltage is? Voltage gauges are notoriously inaccurate. Use a volt-meter or multi-meter.

Most auto parts stores (e.g. Kragen/O'Rielly, Pepboys, Autozone etc) will test your battery and charging system for free. Call ahead of course. Good luck...

 

im using a real volt meter. anyone know where i can get a wiring diagram online?

 

There probably are other places, but I've always gotten the service manuals for my rides from my local dealership. Pays for itself after the first oil change.