I've got a 67 coupe, all original wiring. Hei ignition, new alternator, voltage regulator , battery. Have everything hooked up, start car. The alternator isn't charging, and the gauge never moves either. It should at least show discharge with motor running. I've checked all the wires and are hooked up right. I don't know what else to look for! Has anyone else had this problem ?? Please help- jimmy Ps- the rest of the dash has power!

 

Two issues here - charging and battery gauge indication.

Connect a voltmeter across the battery terminals - engine off should read 12.6V with a fully-charged battery; with the engine running at 1200-1500 rpm, it should read 13.8-14.2V if the system is charging.

Wiggle and push on the plug on the inboard 8-way multiple connector on the engine side of the fuse block to see if that brings the battery gauge to life. Both wires to the battery gauge (black and black/white) go through that connector, and if the connector isn't fully seated or the terminals are corroded, you won't see any indication on the gauge needle.

 

How do you know the alt. isn't charging, did you check the voltage (before and after starting) with a DVM?
Do you have a wiring diagram that shows where the "ammeter" senses the difference in voltages? And did you check for voltage at those two points, or at the ammeter connector plug behind the dash?

 

If its charging, 14 volts or so at the output of the alternator, put a shunt (14g Jumper)across the amp guage, There really isnt any need for all the current to run through that 50 year old guage. This will steady up the guage and take some of the load off if it. Study up a little on these old used cars at Madelectrical.com

 

There isn't any current load on a midyear "battery gauge" - it isn't a series ammeter like you find on C1's. The two wires on the midyear gauge sense voltage at the alternator and at the battery and display the difference, showing whether current is flowing TO or FROM the battery.

 

I TOOK THE ALTERNATOR BACK AND HAD IT TESTED IT'S GOOD. REPLACED THE VOLTAGE REGULATOR( AGAIN). TESTED BATTERY 12V, STARTED CAR 12v NO CHANGE! BIG RED WIRE COMING OFF ALTERNATOR IS HOT, MIDDLE TERMINAL ON HORN RELAY IS HOT, BOTH SIDES OF THE GAUGE ARE HOT!! WHAT ELSE CAN I TRY?? THANKS- JIMMY

 

I've unpluged the wiring harness on the firewall, cleaned and replaced!! Still nothing. Could the gauge itself be bad and not letting the current through it to complete the circut to properly work?? Thanks- jimmy

 

Not much to add except I can tell you how to make a cheap alternator tester for yourself or anyone else wanting to check a alternator on the car....Your correct GM alternator is one with a double wire plug on the back...Buy a replacement plug for that type of alt. and then strip a 1/2 in off each wire and tie them together....Put the new plug in the alt and start the engine....then simply touch the 2 wires together to the 'Red hot post.....If the alt starts to wine it works, no noise, bad alt........

 

The gauge can be bad and not show a charge. But whether it was shorted out or burned open, it would not keep the battery from charging..., unless things were was wired incorrectly.

When the car is running at >2,000 RPM, what is the voltage on the red wire at the alternator and at the horn relay, and what is the voltage at the battery?

 

Please clarify. Did you connect a VOLTMETER across the battery and get 12v with the car not running. Then you started the car and still got the same exact voltage on a VOLTMETER? Did you measure the red wire at the alternator with the car running? If so, was it 12v? Please post exactly the voltage you got under these three conditions and I bet we can track this down.

 

Here is a generic wiring diagram for an externally regulated Delco alternator like the one on your C2:



The horn relay is the junction. The "big red wire" is the regulated voltage output from the alternator. If, as you said, you are getting 12V at the battery and junction with the engine running, you are not getting the expected approx 14V out of the alternator. If we assume the alternator and regulator are good, you need to do the following:

1. Check the voltage at the alternator between the output terminal and ground with the engine running. If it is 14V, there is a problem with the connection to the junction. Check continuity (resistance) between the alternator end and the horn relay end.
2. If there was not 14V, there is a problem with the regulator wiring.
- Check the ground of the regulator. Test continuity between the radiator support and the metal base of the regulator.
- Check continuity of each of the wires between the plug at the alternator and the voltage regulator. There are 3 - F-F, R-2, and gnd. Then check the continuity between the voltage regulator and the horn relay (3).
- Finally, make sure all of the connectors are clean making good contact at the alternator plug, the regulator and the horn relay.

Greg
- A couple of additional notes:
1. How it works: (very simplified). When you turn the key on and the engine is not running, 12V is applied to the #4 terminal which then feeds 12V to the alternator F terminal to create an initial field to get the alternator output going when you crank over the car. Once the alternator output as sensed on the R terminal gets to about 3.2V, the regulator begins regulating the field current (F terminal) by opening and closing the regulator points based on the sensed voltage from the horn relay junction via regulator terminal 3. The rapid opening and closing of the points results in voltage being regulated at about 14V. The voltage at the alternator output will be a bit higher depending on the current draw.
2. If any "add-on" accessories are connected somewhere else than at the horn relay junction (like directly at the battery), it can make the ammeter not work at all.