Bad alternator?

[Cole]

Getting 12.3v at the battery when cranked. Dead cell or alternator?

 

[midlife]

You get this voltage while cranking the starter motor? If so, that's perfectly normal. The alternator isn't working at such low revolutions and the voltage on the battery gets drawn down due to the heavy load of the starter motor.

 

[Don C]

+1, a cranking voltage of 12.3 is very good. Below 10 volts indicates a discharged battery or a bad cell.

 

[Cole]

12.3 while idling. Can charge it and drive around the blocks a few times, then it won't crank. Reved the engine with the lights on and don't see them dim any. There's only 4 things here right? Battery, alt, voltage regulator and solenoid.

Guess I'll take the battery out tomorrow and have it tested. I'd rather have a motorcraft battery anyway to keep the original look. If it's the alternator probably do a rebuild of it to keep it original.

All original parts cept the battery. 38k miles.

 

[Jeff73Mach1]

It could also be the voltage regulator

To test this, unplug the voltage regulator, start the car and jump from the F to 3 terminal on the reg. the alt. should put out it's maximum output of appx 16+ volts, if not the alt is bad, if it does kick the voltage up, just replace the regulator. Only do this for 30 seconds or so, you don't want to burn up wiring.

 

[Cole]

It could also be the voltage regulator

To test this, unplug the voltage regulator, start the car and jump from the F to 3 terminal on the reg. the alt. should put out it's maximum output of appx 16+ volts, if not the alt is bad, if it does kick the voltage up, just replace the regulator. Only do this for 30 seconds or so, you don't want to burn up wiring.

Most Excellent my man! We're gonna have to meet up half way one day. Take some car pics, drink some coffee.

 

[Cole]

The F and the S pins on the regulator Jeff. Thinking you may have fat fingered that 3.

Found this:

Voltage regulator teminal (I) goes to key switch Acc or Coil Risistor

Voltage regulator teminal (A) goes to Alternator Battery Connection

Voltage regulator teminal (S) goes to Alternator Stator Connection

Voltage regulator teminal (F) goes to Alternator Field Connection

This shows the pins: http://www.junkyardgenius.com/charging/ford02.html

Wiring diagram for 73 shows

O-LB Would be the F

LG-R would be the S

Y-W would be the A

LG-R? the I

Let me get my flashlight, and glasses. lollerz

 

[rocket366]

The idea is to "FULL FIELD" the alt. by putting bat. voltage to the field of the alt.

making it max out it's potential taking the V reg. out of the mix.



Paul

BTW this guy has a boatload of good vids

 

[72HCODE]

^ BAD IDEA DO NOT DISCONNECT THE BATTERY WHILE RUNNING!!!!

this usually damages the alternator it also removes the protection of the low impedance of the battery, allowing the alternator to introduce some sizable spikes.

Your battery does more than just provide electricity. It also shorts AC, spikes and transients to ground. Removing the battery from the circuit allows those spikes and transients to travel around, endangering every semiconductor circuit in your car. On a new car this is REALLY bad as it can damage the ECU etc. on our cars this can blow an electronic ignition system. no idea if the car in the video is using points or not. you can buy an alternator tester for under 30$ from sears:

there more expensive ones also. i had my alternator rebuilt by a local guy and he explained to me that old advice of removing the battery to test the alternator is just wrong it can also damage the STAT and there is noise capacitor inside that can become damaged if the battery is removed with the car running.

the voltage regulator is another place to check for failure.

I repaired a members car that had an electrical short which blew the alternator and a new voltage regulator, the car still ran and the lights still worked but the regulator was doing nothing and the alternator was not charging at all. we had to replace the alternator with a spare i had and that was when we found out the regulator was blown also and replaced that all using the actron tester pictured above. we figured out the automatic seat backs solenoid was incorrectly hooked up to the main engine harness that caused a massive short and blew the alternator and the regulator out.

 

[Cole]

It's the alternator. I took the never used regulator off old Rusty (71) just to make sure it wasn't both.

Was so looking at the chrome one on CJPony. Found a local place that can rebuild the original for $70. I'm going that route and they said it was a day or two turn around. I could throw Rusty's alternator on there but I guess I just answered the question I've been asking since I got the 73. Keep it original or add stuff I got for Rusty to add HP to the 73. (Cam, Holley 750, headers). Maybe one day I could have the best of both worlds. One just like it came from the dealer and one that's build for HP.

I do so appreciate the tips and helpful hints. You guys rock.

 

[midlife]

^ BAD IDEA DO NOT DISCONNECT THE BATTERY WHILE RUNNING!!!!

this usually damages the alternator it also removes the protection of the low impedance of the battery, allowing the alternator to introduce some sizable spikes.

Your battery does more than just provide electricity. It also shorts AC, spikes and transients to ground. Removing the battery from the circuit allows those spikes and transients to travel around, endangering every semiconductor circuit in your car. On a new car this is REALLY bad as it can damage the ECU etc. on our cars this can blow an electronic ignition system. no idea if the car in the video is using points or not. you can buy an alternator tester for under 30$ from sears:

there more expensive ones also. i had my alternator rebuilt by a local guy and he explained to me that old advice of removing the battery to test the alternator is just wrong it can also damage the STAT and there is noise capacitor inside that can become damaged if the battery is removed with the car running.

the voltage regulator is another place to check for failure.

I repaired a members car that had an electrical short which blew the alternator and a new voltage regulator, the car still ran and the lights still worked but the regulator was doing nothing and the alternator was not charging at all. we had to replace the alternator with a spare i had and that was when we found out the regulator was blown also and replaced that all using the actron tester pictured above. we figured out the automatic seat backs solenoid was incorrectly hooked up to the main engine harness that caused a massive short and blew the alternator and the regulator out.

I thought the same thing when I saw the video...that was not good advice on the video at all. That guy lost all credibility with me.

 

[Twins]

^ BAD IDEA DO NOT DISCONNECT THE BATTERY WHILE RUNNING!!!!

this usually damages the alternator it also removes the protection of the low impedance of the battery, allowing the alternator to introduce some sizable spikes.

Your battery does more than just provide electricity. It also shorts AC, spikes and transients to ground. Removing the battery from the circuit allows those spikes and transients to travel around, endangering every semiconductor circuit in your car. On a new car this is REALLY bad as it can damage the ECU etc. on our cars this can blow an electronic ignition system. no idea if the car in the video is using points or not. you can buy an alternator tester for under 30$ from sears:

there more expensive ones also. i had my alternator rebuilt by a local guy and he explained to me that old advice of removing the battery to test the alternator is just wrong it can also damage the STAT and there is noise capacitor inside that can become damaged if the battery is removed with the car running.

the voltage regulator is another place to check for failure.

I repaired a members car that had an electrical short which blew the alternator and a new voltage regulator, the car still ran and the lights still worked but the regulator was doing nothing and the alternator was not charging at all. we had to replace the alternator with a spare i had and that was when we found out the regulator was blown also and replaced that all using the actron tester pictured above. we figured out the automatic seat backs solenoid was incorrectly hooked up to the main engine harness that caused a massive short and blew the alternator and the regulator out.

I would be that member and me and my electrical system thank you every time we go for a ride! Oddly, that car ran fine and the alternator was providing just enough juice to maintain the battery but had I tried to use the headlights or any other draw I would be in negative territory. I only realized something was up when my interior lights started pulsing and a voltage meter at the battery while the car was running showed about 12 volts if I recall.

Dan (72HCODE)suffered a few electrical shorts himself when he became the ground when fixing this issue and I cant say enough how great it was to have his help (Let's not even talk about the door hinge rescue he later did!). He has an amazing knowledge base about these cars.

 

[72HCODE]

i still laugh about fixing the seatbelt and key buzzer stuff and getting shocked.

always disconnect the battery with the car off and making electrical repairs, lol

12 volts at high amps hurts.

Jeff can you believe its been like a year where does the time go,, fast when it rains every single weekend.

 

[wwhite72]

my default response is the VR because the originals lasted a while but the overseas cheap replacements never lasted long at all. Also the grounding is always a concern. The wire that goes under the lower VR mounting bolt always seems to get rusty or loose. Had to sand the spot on the firewall to get a good ground. my problem with alt was bearing rather than output. i put in a transistor VR and never had another problem.

 

[Cole]

Southern Armature B'ham did a good job rebuilding this. About the only time I have to put it back on is when the lil one is asleep and the car is right below her bedroom. Nah, man Monday is good. LMAO School starts back and I'll have plenty of time. These guys only do alternators, starters and radiators. Been in business ??? well my dad said he used them when he was a young man. They polished the casing, new housing bolts, either thats a new shaft or it was polished.