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Alternator/Battery problem...Heck! I don't know

777 views 11 replies 8 participants last post by  AustinGT 
#1 ·
Jeep won't start. Here is the timeline.

Two weeks ago...battery was ded. Got a new one and worked fine for a week
One week ago...new battery was dead. Took off the alternator and batter and had them tested, both came back infe (one guy did say the battery was over charged). Put everyting back together and still would not start. I jumped the jeep and it started up and let it run for 20 minutes. Shut it down and it started right back up. Ran fine for a week....until today.
Today....I went to start it and it won't even turn over, but it will start when I jump it (in all cases it was able to be jump started)

Here is the weird thing, when the car is running I can take off the negative battery cable and it will run fine (tells me the alternator is working to some degree) and when I ran the car for that twenty minutes the alternator appeared to charge the battery, but two guys said the battery was fine when I tested it. I am baffled. Any suggestions.

:brickwall

I can be reached on AIM and IM if you can chat.

PLEASE help,
AGT
 
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#3 ·
or bad ground (inc the one for the rear of the block to the firewall)

or dirty battery lead connections .. or the one on the starter

or the starter is FUBAR
 
#4 ·
I had a ranger that did the same thing! I changed the alt. twice no luck it was as simple as the neg wire loose. On my old truck there were 2 wires to the neg. the thinner one had the wires boke off inside so that you couldn't see that it was not getting a good conection try redoing the wires !
 
#5 ·
Try checking your terminal to clamp resistance with a multimeter.

IF your battery was tested fine and you still needed a boost to start then it needed more power.

Increased line resistance is one casuse. Bad connection is another. Both require more power to start and that is what a boost is giving you. Remove the cables and clean all connections then test the resistance of the cables. It should read very low if not replace.

Also use your multimeter and check the voltage after it has been running, then check it after it has been parked for a long time. The reading should be over 12.5 v, 12.7 would be better. If you have a readign of 12 or lower you have a problem, either with the battery or some unknown draw on the system.

A multimeter is the key to diagnose this situation, because youcan start eliminating what it is not and localize the problem.

Hope that helps.
 
#7 ·
Thanks for all the help guys. I am pretty dumb when it comes to electrical stuff. I hate to admit it but I don't know how to use my voltometer that I have. So some direction in that would be helpful.

I also noticed something else. When I pull the negative cable off the battery for a while, I am able to hear the buzzer when I put in the keys and trun on the lights. But when I try and turn it over, everything then goes dead. Does this help?

AGT
 
#8 ·
I noticed that you said you disconnected the negative terminal of the battery and the engine kept running. When you disconnect either of the battery terminals it creates a surge (spike) in the alternator voltage (provided of course the alternator is working in the first place) that can destroy voltage sensitive components, radio's computer etc. Check if it's charging with a multimeter. If you can do this here is a "quickie" test to see if your alternator is working. Hold a ferrous metal object (screwdriver tip) at the rear bearing of the alternator. If the alternator is working you will feel a magnetic pull.
 
#9 · (Edited)
JFM626 said:
I noticed that you said you disconnected the negative terminal of the battery and the engine kept running. When you disconnect either of the battery terminals it creates a surge (spike) in the alternator voltage (provided of course the alternator is working in the first place) that can destroy voltage sensitive components, radio's computer etc. Check if it's charging with a multimeter. If you can do this here is a "quickie" test to see if your alternator is working. Hold a ferrous metal object (screwdriver tip) at the rear bearing of the alternator. If the alternator is working you will feel a magnetic pull.
I got some new information for you all. I am standing in fron tof my jeep (with my wireless laptop....gotta love technology) and I can't jump it now. When I try to I get the buzzer like it has juice but when I turn it over....nothing. But I do get a nice spark on the positive terminal of the battery, even when the terminals are not connected to the battery, and I have them connected to the jumper cables. Any ideas now?

AGT
 
#10 ·
You haven't said what engine you have, but I am going to assume that the starter solenoid is on top of the starter, and not on the fender near the battery. Leave your jeep battery connected to the starter for this procedure. At this time do not connect to the jumper battery! Using the jumper cable with the red end connect it to the starter on the same stud that the cable from the battery goes to. Using the cable with the black end connect it a good ground on the engine block, make sure that the area you clamp it to is free of dirt and paint; in other words bare metal. If you can clamp it to the same bolt that the cable from the negative terminal of the battery goes to on the block thats good. Do not connect it to the jeep battery though. Now take the other end of the cable with the red end and hook it to the positive terminal of the jumper battery. Take the other end of the cable with the black end(the one you connected to the ground on the engine) and connect it to the negative terminal of the jumper battery. Try to start it with the key. If it turns over and starts you have eliminated the starter and the wiring from the ignition switch as a problem. If you still get nothing, make sure your connections are all good and try again. If you still get nothing, have a look a the starter and you will see a small wire attached to a connector near where you have the red ended jumper cable end. Turn the key to the run position. Using an insulated scewdriver (one that you consider expendable) touch it at the same time to the red ended jumper cable end and the small connector. If the starter now turns over; the starter is OK but the wire from the ignition is not. See how that goes.
 
#11 ·
def sounds like a wiring problem somewhere in the starter loop. when my monte carlo was doin pretty much the same thing (it just went dead one day, not intermittent like yours), the wire from the ignition to the starter was dead, so it wan't closing the circuit when i was turning the key, hence no clicking or anything. Hope this helps, good luck
 
#12 ·
I got it started. I am embarassed as to what the problem turned out, but I will get to that later. I took off the starter thinking that it was bad and took it in to get tested, but it tested fine. So the battery, aternator, and starter was good. The next thing that I thought was that I was going to have to replace the wire harness, but before I did that I thought that I would change out the terminal connectors. After doing that...it worked. So what is the lesson to be learned? Start with the simple stuff and work your way out.
 
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