Grounded ?

[rsparks79cj7]

Hi guys, I have a question about a ground for the alternator. My CJ7 is a 79 with a AMC 258 i6 / 4.2l HEI and no other engine mods, she is my DD. About a weak ago my alternator quit charging, so picked up a new one and it wouldn't charge either, I took it back and they replaced it with another one. Installed this one and it worked fine, well a little to good according to the volt meter it was putting out 16 volts on acceleration, at idle it was 12-13 volts. As soon as you push the throttle it jumps back up to 16 volts, could there be something wrong with the volt meter, wouldn't the wiring get a tad warm if it was actually putting that much out? My Father-In-Law Has a cheap hand gauge of some sort, never seen anything like and said it was allright ??? Back to the ground question, is there a place out of the way or behind the dash the alternator is grounded to? Driving along, hit pot hole and the alternator quit chaging again, checked all the bolts and the belt is tight, Im thinking that the original alternator was probably ok and I hav a loose ground or some other connection. I have checked all the connections I can find. Thanks for any and all help. It is the stock alt.

 

[BusaDave9]

The alternator should put out 14 volts. As you rev your engine the voltage regulator built into the alternator should keep the voltage under 14.5 volts. Do you have a good meter? How are you reading it? Is the volt gauge in the dash bad. Maybe your father in laws meter says it's good.
You say you hit a pot hole and it stops charging. How do you know? Once again could it be a bad volt meter on the dash?

The alternator is grounded by the bolts and brackets that hold it on. No other ground is necessary.

 

[rsparks79cj7]

The volt meter in the dash has allways worked fine. If I have to crank the engine on a cold day 2-3 times and it starts the volt meter has allways read 14-15 volts, after it tops off the battery it drops back to 12 volts, so it's worked fine in the past. After hitting pot hole it stopped charging, the battery was low and the volt meter read 10 volts, after the sudden jarr. The Battery Voltage continues to drop while driving, Brake lights, horn, any electrical draw continues to lower the battery voltage, alt. not working. Is there any other connections that could be loose between the alt. and, werever it goes, the ignition switch, or werever? Again thanks for the help and answers.

 

[BusaDave9]

The alternator and the battery are both connected to a post on the starter solenoid. There is no other circuitry involved. When the engine is not running you have have the 12 volts from the battery at that post. When the engine is running the alternator is putting out 14 volts. The only connection it could be is the one on the alternator. You have a new alternator so it is unlikely (but possible) that is your problem. If the problem was the connection on the big battery cable then the problem would be during starting when you draw the most current.
Since the voltage drops when you hit a bump is sounds like it might be a short. When it drops below 12 volts it may be shorting to ground but it would have to be a high current short. You would be able to see burn marks. If you opened the hood when the voltage was 12 or less volts you would even see electrical arcing.
If you didn't replace the alternator I would say it's bad. Was it new or used?


Okay, so you are driving along and you notice the voltage is low. If the voltage is ever 12 volts then then your alternator is not working. If it ever goes below 12 then you have been running on battery alone and it has been discharging for a while. Does the Jeep faile to start after the voltage drops low?
OEM volt meters in the dash are not very accurate but when they go bad they almost always read as low as they can go. Even though it doesn't sound like a problem with your in-dash volt meter you may want to rig up another volt meter for when you drive.

 

[rsparks79cj7]

Thanks Dave I appreciate the help, the first alt. had been on at least 10 yrs. and I have never had any problems before. The pot hole prob. just happened 1x and that was after I replaced the old alt., the alt. hasn't worked since, never had the prob. on the old alt. Sorry for any confusion, and again thank you for the help.