Driving home at other night and lights went dim. Were would you start?

If you don't have a meter to test battery/alt output (you should) you can start with the poor mans test, a screw driver tip to the back of the alternator shaft bearing located in the center at the rear of the alt case, as the vehicle is running, you should have a strong enough magnetic charge to hold the screw driver tip to it, if there's no magnetism, then chances are no output on the alt, if there's output but the battery is not charging, then chances are the voltage regulator, a battery that's given up the ghost, or a wiring issues...get a meter, you need it to take the guess work/ghosts out of the picture

I do not have any volts at the back of the alternator. I clean the plugs at the firewall still no volts. Can anyone tell me were to check next?

No volts where?

There's more than one wire at each of those spots.

No volts at the large terminal on the alternator, check your fusible links, one is probably burned.

No volts at the large terminal. There is only one fusible link right up by the battery. Or is there another one? I have power to the car to start it and the lights. If that link is blown I would not have anything. I not remembering another link.

A factory service manual would tell you these answers.

I do not have a 73 Cuda nor a manual for one, sorry.

correct, no other link. see if the black wire out to the alt main stud is hot at the bulkhead (should be all the time) & either work downstream toward alt (fairly rare as it is a straight wire (no terminals/connections) or go upstream under the dash toward the "welded splice" for the open

So it sounds like you have a voltmeter since you see zero volts at the alternator output stud. Then use the vmeter at the battery posts while it is running. What voltage reading are you getting? Should be around 14v. If you are only getting around 12v, then alternator is probably shot. You can also take the alternator off and take to your local parts store that can test it.

so that doesn't sound right.
you should have battery voltage not 0 at the back of the alt.
The large stud should be hot all the time.
If there isn't battery voltage there, you have a break in that line somewhere.

What are you using as ground when you check that voltage?


Key on, you should check each field. one should also be battery voltage, the other will be something less, like 3 volts or so.

Again, if you aren't getting battery voltage there, start checking lines.

I just took the alternator and it is good will be looking at that main wire to the back of the alternator. Anyone got a wiring diagram on were that wire gos? I have one here somewhere may have to find it. Lol Need to get 12 volts back.

IIRC, on my '73 'Cuda there was a plug in the alternator harness wrapped in tape right about even with the carb. I had it come unplugged once.

I will look for it.
thanks!

The Wire from the alternator stud goes pretty much straight to the battery and should be hot all the time. Between the main stud on the alternator and the battery are the following connections.

Alternator goes to a multi-wire disconnect located at the rear of the passenger side valve cover in the wiring harness. This was something that was started around 73 (maybe 72?) and earlier models do not have it.

It then goes to the bulkhead connector. (1st of 2 large wires)

From the bulkhead connector it goes to a splice buried in the wiring harness (the splice itself is rarely a problem)

From the splice it goes to the ammeter gauge.

From the ammeter gauge it goes to the bulkhead connector. 2nd of 2 large wires.

From the bulkhead connector it goes to the fusible link .

From the fusible link it goes to a terminal on the starter relay.

From the terminal on the starter relay it goes to the battery.

As you have said the fusible link will leave the car dead.

If you have any voltage at the voltage regulator connections then you should make voltage at the alternator stud. Since the connection to the battery is nearly direct you should have voltage even if you disconnect the voltage regulator. So, If the motor is running and you have no voltage at the alternator, then it means you have BOTH a problem with the voltage regulator, (bad connection or a bad voltage regulator) AND a broken connection between the alternator and the battery. Check the connector at the rear of the motor first.

Most common problems are the connectors at the back of the motor and the bulkhead. Check them first.

Ok got it fixed up it was the plug by the back of the motor. It melted so I jump around it. Also ran a wire straight to battery from the alternator. Must of pulled to much power when running the air. May also put a fuse at the battery. Anyone know what amp fuse would be right to use? It has to run the car but not the starter of course.

You would not want to use a fuse. I would clean the connection you identified & call it good. unless the system was overcharging then it was just a poor connection that melted that terminal/connection that you found. wouldn't hurt to clean ALL connections/terminals. if you keep the ammeter close to 12 0'clock you will be fine. going from batt to starter relay does take some load off of the bulkhead but renders the ammeter reading inaccurate. some people like that mod some dont. if you (A) keep the bulkhead cleaned (B) keep ammeter needle close to 12 0'clock with the rest of the connections/terminals cleaned you will have zero problems

You do know if you ran a wire from the alt right to the battery the amp gauge will not read right any more. Which you can just add a voltmeter to a 12 volt key on wire like the J2 circuit to moniter running volts and know if it charges. On my 63 I have the battery in the trunk and on my output wire to my alt I use a 70 amp type of large fuse that is the kind with eyelet terminals on each side. I bolted one side to the battery cutout switch in the trunk end and the other side I bolted to the eyelet terminal on the 10 gauge wire that goes to my alt output. I would definetly put a type of fuse or fuseable link on the wire you ran to the alt output terminal. My alt is a 60 amp unit and thats why I used a 70 amp fuse so depending on the output of your alt will depend on the fuse you should use. You need to use the larger type fuses that will work ok with the amps that will flow and not burn out to fast from the normal heat buildup. Thats why they used fuseable links in the older days as they can get warm when the alt is putting alot of amps back into the battery if the battery gets low and the fuseable links could handle the normal heat and not burn out to soon from it. The large 70 amp fuse I use on mine with the eyelet terminals on both ends of it has worked good in my car as its been in it since 2006. Ron

actually a fuse would work just not a regular automotive glass type fuse which I was thinking you were thinking! It'd have to be a specialty type. there was a thread on that, I shoulda copies what they said to use. the wiring on my old '66 dart was flowing too much for some reason (was way back) iirc it full fielded-bad reg, to the point where the outside insulation in a long stretch of wire shriveled & the FL still never went open

A fusible link is better than a fuse and there should already be one at the starter relay. If it burns you should replace it with another link not just a wire.

If you go with a fuse get a large fuse like you would use for a stereo amplifier and start small around 30 to 40 amps. If you look at all the stuff these old cars had there wasn't a lot of current draw. Most had no power windows or seats etc. Lights, ignition, radio, AC/heat and wipers, PRetty much sums it up.

Wires were used instead of fuses because they would take in rush current surges without unnecessarily opening. That said, excessive current had to be present for some time for the fusible link to open. Usually there was collateral damage to other wiring at that point. If you kill the power immediately when you smell the link insulation burning, you could keep damage to a minimum.
If you do put in a fuse, make sure you have boxes of them in the car as surges will kill them and leave you high and dry.