I have an 85 CJ7 with a 258. Until today the volt meter has measured a solid 14 while the engine is running no matter the rpm. It sat for a couple of weeks and I had to jump it today and it fired right off. I noiced that the volt meter fluctuated from approx 11-16 bouncing around. While driving it is right at 16. i drove several miles to work and it just clicked when I tried to recrank it. It then jumped right off. Long story short, do I have an alternator, battery, or other problem that I havent thought of??
Battery's don't like being dead for too long. The sulfate gell hardens and kills the battery
I'd you have a charger. Charge it and see if it holds a charge. It probably won't.
If not replace battery. If it does check alternator .
Would a dead battery cause the high voltage readings?
Use a voltmeter to check the battery voltage should be about 12 volts if its not then jump it and check the bat voltage again, if its around 14 volts with the engine running then the alt is fine and the battery is shot. if it is not 14 volts double check all the wiring from the alt to the battery, if all the wiring is fine then the alt probably needs to be replaced.
There is also a chance that both are shot, you can check the battery by charging it with a battery charger and then checking the voltage across the terminals. If it holds a charge then the battery should be fine.
You can also take the alt and battery to any auto parts store and they will test both for free.
Edit: the voltage guage in the dash is more of a voltage indicator. A good multi meter will really let you know what's going on.
I'd say you have a diode burned out in the rectifier.
When a rectifier diode goes out, you get all kinds of strange things going on with the regulator since the regulator 'Samples' the line voltage from the alternator it's self...
(The 'Small Red' wire that goes from the two wire plug to the back of the alternator)
And since the battery ran down, a bad diode in the rectifier WILL allow the battery to drain over time.
There isn't much else that can go wrong that will do both run the battery down over time and screw with the voltage regulator...
I'd take it to the local auto parts store, and have them run a FREE test on the battery/charging/Starting systems to see what EXACTLY is going on.
If they say 'Alternator', then have them test the old alternator before you buy a new one, and I would wager they will tell you the rectifier diodes are cooked.
when mine did this, i had a worn out ring connector bw the alternator and the solenoid. check all connections.
Wouldn't discharge the battery as it sat.
Worn out 'Ring' connector would have kept the battery from charging in the first place...
Worn out 'Ring' connector should have been the 'Fusible Link' connection to the battery cable at the starter relay.
Did you just change the terminal or change the entire Fusible Link?
Don't run without a fusible link or fuse!
That 10 Ga. wire gets against the exhaust manifold or gets pinched against the block and you stand a pretty good chance of a fire without a fusible link or fuse in that wire!
by worn out i meant the wire was broken and creating an open circuit. so most of the time the alternator was not charging and the battery showed about 12 v. occasionally i would look down and see it jumping up and down, so it was connecting with vibrations or heat expansion or dumb luck. the battery did eventually die and that is when i started inspecting everything. the ring connector was on the fusible link so i put a new ring on and the link is still in place and now there is a always a steady 14v (or whatever its reading above 12)
THIS GUY had a battery run down sitting still, not running the engine.
Something has to be sucking amps while it's not running...
And the only thing I can think of right off hand that will screw with charging,
AND RUN THE BATTERY DOWN SITTING STILL,
Is a popped diode in the Rectifier... Connected directly to the large 'Red' wire on the back of the alternator.
When the diode goes bad, the rectifier can drain the battery,
And when a rectifier goes, you get AC voltage into the 'Sense' circuit of the regulator, so the regulator does strange things, like over charging.
AC voltage is VERY BAD for the battery, and everything else on the vehicle,
So getting it tested/repaired REAL SOON is a very good idea!
hey man i am just offering up my experiences that had related symptoms. stop being a ****** bag. my experiences are not even directed at you. isnt this the kind of crap that you usually complain about others?
No, not at all, your 'Experiences' are your experiences,
And unless you want people calling you names, don't call others names.
However I do take offense when someone INSISTS they are correct,
When what they 'Experienced' can't cause the symptoms the OP is talking about.
Your gauge told you the charging was intermittent, and over time while DRIVING the vehicle, the battery finally failed to get enough charge to start your engine.
Good catch on the 'Ring Terminal', and that would cause exactly what you described happened to you...
On the other hand,
Not at all like the symptoms the OP posted.
He said the battery ran down while PARKED, and I quote,
Could be a bad battery not holding charge...
But with this,
Could be a bad battery AND a faulty voltage regulator at the same time,
Or a bad battery and the 'Sense' wire to the regulator plug not making good contact...
But showing a solid 16+ volts when the engine was off idle,
That suggests a bad regulator or 'Sense' wire signal that is UN-Interrupted.
Could be a deeply discharged battery playing hell with the regulator...
But a PROPERLY working regulator should NEVER exceed 14.5 volts, no matter what the condition of the battery...
Since there are some other troubling statements...
Either way, it shouldn't cause an over charge condition...
And if I'm correct in my guess, you can bet the regulator is shot, and if he went very far in the 'Several Mile' trip to work and back,
The battery stands a good chance of being 'Junk' from the AC voltage being thrown at it from the failed Rectifier...
Another good reason for a FREE test at the local auto parts store...
SO! After taking all that in, I suggested a possible cause for the overcharge/dead battery that made sense for both,
I went on to suggest a FREE battery/charging/starting system check to make sure it's NOT something else going on here...
SINCE I DON'T HAVE A CRYSTAL BALL,
And the OP didn't give details (They usually don't give much information),
Like what was battery voltage when the engine wouldn't start the first time or the second time?,
If the battery cables/terminals had been serviced recently?,
IF the battery had been checked for electrolyte level?,
I suggested a Battery/Charging/Starting system FREE check up...
I guess once the OP has the FREE test done, we'll know if it was a 'Ring Terminal' or not.
And on the subject of YOU...
Since the 'Ring Terminal' is supposed to be molded onto the Fusible Link wire end,
It's quite impossible for the 'Ring Terminal' to wear it's way off the wire unless someone has removed the Fusible Link and replaced it with a regular piece of wire without a molded on 'Ring Terminal'...
ALL FACTORY AND REPLACEMENT FUSIBLE LINKS HAVE THE MOLDED RING TERMINAL TO IDENTIFY THEM...
AND TO KEEP THEM FROM DOING EXACTLY WHAT YOU SAY YOURS DID...
That suggests someone has removed the Fusible Link from your system and replaced it with a regular piece of wire and crimped on 'Ring Terminal'... And that ill conceived 'Patch' failed on you, and you didn't know about a 'Fusible Link' so you didn't know it was supposed to be in there.
In which case that vehicle would be at risk of burning down If/When the primary wire gets melted, rubbed through or pinched,
Or the alternator it's self gives up and grounds out.
I was trying to GENTLY steer you towards having a second look at your own system for safety reasons.
Without a Fuse/Fusible Link in that primary wire, it's not a question of "IF" it's going to burn down,
It's a question of WHEN it's going to burn down...
It's your vehicle, do what you want.
But for $5 it's a pretty good safety device to have installed.
Did the op ever find his problem? I have a 86 and same problem. I am going to swap out my alt today and see what happens.
I cant say positively that I have solved the problem. A volt meter on the old battery showed 12.4 volts without the jeep running. The heater fan would run, and the lights would turn on but very dimly. When the lights were turned on the volt indicator dropped out to nearly zero. I put the battery on a charge, but it didnt seem to help. It recently snowed so I had to do something as this is the only thing I have that is 4x4, so I snatched the battery out of a grand cherokee last night, and everything appears to be back to normal. So it appears that it was a bad battery but I cant really back that up as it has only been 1 day with the new battery.
It was the battery. I took it to the parts store for testing (and to get a new one). It was fully charged, but needed replacement. With the new battery all indications (voltage fluctuations) are that the problem has been resolved...
Thanks for reporting back on the solution. Many times things get solved but post don't get updated.
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