[1978CJ7Jeep]

Maybe this will be a quickie. My 1978 CJ7 has been over charging. Like most everything today - parts come from China. When I start up, the ammeter gauge reads just over 12 volts. When I rev the engine to about 1400 RPM, the gauge jumps to near 16 volts. With everything running (lights, heater blower on High, turn signals on, brake pedal pushed, wipers on) the voltage drops to about 14-15 volts.

The battery is a quality battery and only about a year old. When the voltage reads reads high - the head light beams are REALLY bright. I'm certain I'm not getting a false reading from the ammeter. Once I have revved the engine and get that high voltage reading - it stays high - even when I let the engine back down to idle speed.

I replaced the alternator twice with rebuilds from O'Rielly Auto Parts but still the same issue. I've never changed an internal voltage regulator in an alternator, but that looks like maybe my next move.Again with parts today, I just resolved an oil pressure reading after changing out 3 different new oil sending units. I hope not to go thru the same thing with voltage regulator issue.

If it IS the voltage regulator (and if this sounds to you like the issue) - can anyone recommend a GOOD voltage regulator or a source for a dependable replacement? 16 volts seems pretty high.

 

[1978CJ7Jeep]

Nobody has this issue? I just got back from town. Took the alternator to O'Riellys - they checked it for output and (no surprise) it generates electricity. Problem is that their machine doesn't measure the voltage. THAT is my problem: TOO much voltage. I bought a voltage regulator and just finished putting it in the alternator. Dang thing (like everything else today) it is also MADE IN CHINA. I'll put it back on the Jeep in the morning and see what happens.

Side note: taking the alternator apart isn't very difficult. Only real trick is to have a straightened out safety pin to place thru the hole on the brush retainer to keep the brushes retracted when you re-assemble the case halves. After you get the case halves put back together just pull out the safety pin to let the brushes ride where they are supposed to.

Got my fingers crossed and will see if the new voltage regulator works like it is supposed to.

 

[divedivedive]

Nobody has this issue? I just got back from town. Took the alternator to O'Riellys - they checked it for output and (no surprise) it generates electricity. Problem is that their machine doesn't measure the voltage. THAT is my problem: TOO much voltage. I bought a voltage regulator and just finished putting it in the alternator. Dang thing (like everything else today) it is also MADE IN CHINA. I'll put it back on the Jeep in the morning and see what happens.

Side note: taking the alternator apart isn't very difficult. Only real trick is to have a straightened out safety pin to place thru the hole on the brush retainer to keep the brushes retracted when you re-assemble the case halves. After you get the case halves put back together just pull out the safety pin to let the brushes ride where they are supposed to.

Got my fingers crossed and will see if the new voltage regulator works like it is supposed to.

I had this EXACT issue - it was 100% the voltage regulator.

Unfortunately it looks like your '78 has a different regulator than my '75.
I used this: Standard Motor Products VR-115 Standard Motor Voltage Regulators | Summit Racing

Sorry I'm not better help finding you a direct replacement part.... But I'm confident the regulator will fix your problems once you track down the correct one.

 

[1978CJ7Jeep]

Your '75 uses an external voltage regulator just as you described. I changed out the internal regulator last night and will put the alternator back on today when it warms up a little.I posted this to maybe help someone out in the future. Replacement parts are a crap-shoot these days because most of what we used to make here in the U.S. is farmed out to slave labor countries like China.They don't care about quality - just as long as they make money to support their military machine.

Changing out the part wasn't too difficult. Like everything else when working on electrical components, the key is to keep organized and keep everything as clean as possible to prevent contamination and shorting. That high voltage problem led to false readings on things like my oil pressure gauge.I was also worried about toasting my battery.

 

[1978CJ7Jeep]

End of story: I installed the alternator with the new voltage regulator. The charging rate still seems high, but better. The maximum voltage now reads 15 volts. With everything electrical on (headlights, heater blower on high, turn signals on) the voltage drops to 13-14 volts. I don't think I am in danger of over charging the battery. Time will tell....