My New CJ s***s the bed

[CJ]

When running you should have about 14 volts at the battery while charging, if the voltage is less then your alt or reg. is probably bad.

 

[Gurpgork]

When running you should have about 14 volts at the battery while charging, if the voltage is less then your alt or reg. is probably bad.

Reg?

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[Old Dog]

Reg?

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If you are running a chevy alternator there is a built in voltage regulator.

 

[CJ]

Regulator, internal or external.

 

[mtnwhlr]

A quick way to test your alternator is to start it up and with it running take off the pos batt cable if it dies you have a bad alternator if it stays running its fine.

 

[jasonmark1993]

Since you are a jeep owner now, I strongly suggest buying a voltmeter. 25 bucks at autozone.

With the vehicle running, check your batt voltage. 13.8-14.2 is proper running voltage. Turn on all the lights and signals, wipers, etc. Should still see somewhere in that range.

 

[Gurpgork]

Since you are a jeep owner now, I strongly suggest buying a voltmeter. 25 bucks at autozone.

With the vehicle running, check your batt voltage. 13.8-14.2 is proper running voltage. Turn on all the lights and signals, wipers, etc. Should still see somewhere in that range.

I'm an EE. I have a few voltmeters lying around

 

[thiswontbetooexpensive]

I'm an EE. I have a few voltmeters lying around

And you probably know what all the settings are for too! You have me beat if you do, All I understand is Ohms and volts the toher stuff is like :dunno:!!!!

 

[Gurpgork]

Ok, I was able to identify the alternator as the problem. 12.5V at the battery while running and the engine died instantly when the positive connection was removed from the battery. So I have two questions:

1) Rebuild or replace?
2) Do I need to replace my battery too?

 

[Gurpgork]

Or not.... I pulled the alternator and brought it to AutoZone. They tested it and said that there is nothing wrong with it.

Test results:
battery volts 15.11
ripple volts .36
lamp on volts 2.04
lamp off volts 14.98
rated amps 63
lamp/diode trio: passed
regulator test: passed
rectifier test: passed

Now what?

 

[jasonmark1993]

Ok since its internally regulated that means you must have a connection problem between the alt and batt.

Do a voltage drop test to find the problem and bingo.

 

[jasonmark1993]

I'm an EE. I have a few voltmeters lying around

Not giving you at all because I really don't know, but as an EE, doesnt that knowledge kindof crossover to auto electrical systems.

Or are the two fields just too far apart to apply the knowledge?

Are you familiar with a voltage drop test in an auto application?

 

[Gurpgork]

Ok since its internally regulated that means you must have a connection problem between the alt and batt.

Do a voltage drop test to find the problem and bingo.

Ok, that's next!

 

[Gurpgork]

Not giving you poopie at all because I really don't know, but as an EE, doesnt that knowledge kindof crossover to auto electrical systems.

Or are the two fields just too far apart to apply the knowledge?

Are you familiar with a voltage drop test in an auto application?

The basic ideas are the same. I just thought I'd go for the low hanging fruit first. I assume a voltage drop test would be to measure the drop in voltage across the wires from the alternator to the battery? I should also be able to "ring it out" to check for open wires.

 

[jasonmark1993]

The basic ideas are the same. I just thought I'd go for the low hanging fruit first. I assume a voltage drop test would be to measure the drop in voltage across the wires from the alternator to the battery? I should also be able to "ring it out" to check for open wires.

Not familiar with "ring it out" but ya check for opens. In auto, alot of times the circuit won't be open but you'll see the voltage drop under load.

I would do the voltage drop with the engine off first and then with it running and with the load on it.

Who knows, you put that alt back in and maybe the bad connection was at the alt. Is it just a straight wire from the alt back to the batt or did the PO fuse it or do something funny?

 

[Gurpgork]

The whole wiring on the Jeep is terrible. I'm saving the money for a painless harness replacement. I would be willing to bet the problem is electrical. How do I keep the engine from starting when performing a voltage drop test?

 

[jasonmark1993]

I think your EE and the auto field is causing a gap here. Not sure what you mean by not letting the engine start during the voltage drop. The pos wire from alt to batt has voltage present running or not.

Example of a voltage drop: the difference in voltage across a connection, wire, circuit, etc.

So lets say your truck wont start but you have a fully charged battery. This could be a bad connection (voltage drop) at the terminals. You would put one lead of the VOM on the BATT post and one lead on the cable end. If there is no voltage drop, the meter reads 0.0. If it were a really bad connection, the meter will read 3.2 for example. That is the difference between batt voltage and what the cable is seeing; you have a 3.2v drop. Sometimes you will have a very small or no voltage drop until you put it under load (trying to crank or turn lights on) and walla, now the poor connection fails and you have a huge voltage drop.


So in your case, put on lead on the POS term of the alt. I'm not real familiar with your model so it should be the big wire that runs to the batt. Put the other lead on the poss. batt terminal. You should see 0.0 meaning a perfect connection. This isnt really possible because you lose a little at every connection. I'm guessing you'll see a higher number. To isolate the problem, start working the lead you have on the poss batt terminal back towards the alt. ONE CONNECTION at a time. So from the batt, to the cable end at the batt, then to the fuse/fusible link in the wire, then you should be at the alt.

Maybe take a picture of your setup; I'm sure that explanation was confusing. Id would help if we knew what the connection between the alt and batt consists of. There is usually a fuse/fusible link in there. Sometimes a simple hands on test will reveal the problem. Touch and wiggle all connections and wires related to the problem circuit. Look for bulging wires near the connections (corrosion).

If you don't have a drop, turn on the headlights and flashers and retry.

Im strapped for time today, but I can post a video of this test later tonight or tomorrow for sure.

 

[jasonmark1993]

Whats up man? Did you reinstall yet? Results?

 

[Gurpgork]

Up and running. Needs new wiring. Lots of voltage drop. Took the top and doors off today and went for a spin on backroads. Very rough but fun

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[jasonmark1993]

Ok, but to get the charging system up and running it should just be one wire up to the battery, right?

So you still arent getting charging voltage at the battery?