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-   -   Complicated Electrical Problem (http://www.wranglerforum.com/f218/complicated-electrical-problem-226013.html)

jfallon83 03-07-2013 05:38 PM

Complicated Electrical Problem
 
Hi,

I have a very perplexing electrical problem and need some help. I should start out by saying that I am not a novice (worked at a U-Haul repair center for 6 years and have mechanical engineering degree), but this problem is something that I have never seen before.

I have a 95 YJ with the 2.5 and 5 speed. It has 125,000 miles and I don't think came equipped with any extras (A/C) and it essentially bone stock except for some bfg A/T tires.

About a week and half before this problem started, my battery died when I left the light on all night. It had been in there for 4 years and had finally bit the dust, so I replaced it.

Like I said, a week and half goes by and I go to crank the jeep and it has no power at all. No power to any of the accessories and will not even attempt to crank, not even click.

I had to get to work, so I threw some jumper cables on there and it cranked. I have about an hour drive to work, which should be enough to at least partially charge the battery. To test this, when I got to work I turned off the vehicle and immediately without waiting a second tried to crank it back up. It still acted as if it had a stone cold dead battery. Not even a click to try and turn the motor and the accessories would still not come one. No headlights, brakelights, reverse lights at all.

Jumped it again to get home. I noticed on the ride that it was charging a little high. Around 15 or 16 volts according to my gauge. Not quite in the redline area.

Get home and start testing:

Took the battery completely out of the Jeep and according to my multimeter, it is fully charged.

Pu the battery back in the Jeep and according to my multimeter, it is getting a full 12 volts at the starter.

I tested both of the battery cables downstream to ensure that the cable were well connected. They tested fine.

I pulled off the alternator and took it to Autozone (I did not think this was the issue, but I just wanted to check) and it tested as being in perfect condition.

I took off the dash and removed the ignition switch. It was receiving power and all of the proper outgoing wires got good signal at the right times when I cycled through the ignition.

Went back to the starter. With the help of a friend, tested the remote ignition wire coming into the starter solenoid. I did not get any power when he tried to crank it by cycling the ignition switch. I then took a screw driver and jumped the solenoid leads and it fired up.

I'm completely stumped, because it looks like I might have a short running to my starter from my ignition switch. However, if that is the case then why will the accessories not turn on. Also, why would jumping it using jumper cables fix this problem, if the battery is already fully charged and the cables have a good connection.

I could use some serious help if there is anyone out there who knows the electrical systems on this jeep better than I do.

Thanks in advance.

173ABN VN 03-07-2013 06:28 PM

might try checking your connections on the steering coloumn up under the dash...russ

jk'n 03-07-2013 06:56 PM

Since accessories are out as well as the start function my mind goes to the fuse box. Have you checked fuses for an open one? If it is not a fuse it helps to have a wiring diagram. You will then be able to check out the starting circuit. There is a small relay on the fire wall for the ignition circuit. Try locating that and checking it out as well after you verify that no fuses are open.

Captainrichhill 03-07-2013 07:05 PM

Quote:

Originally Posted by jk'n (Post 3473693)
Since accessories are out as well as the start function my mind goes to the fuse box. Have you checked fuses for an open one? If it is not a fuse it helps to have a wiring diagram. You will then be able to check out the starting circuit. There is a small relay on the fire wall for the ignition circuit. Try locating that and checking it out as well after you verify that no fuses are open.

I'm with him:
There is a start relay that kills your accessories when you crank the engine so you get full battery voltage to the starter. I would ask around at the parts place if they have a start relay of smoe sort. Im not sure which one it is in the Wrangler. Maybe someone else on the forum knows.
Double check where your electrical is grounded to the block also. I found mine loose.
Hope this helps. Keep us up on your findings.

Rich

jonathan75 03-07-2013 07:09 PM

I am starting to think all YJ's need one of these under the front seat.

Power Probe III Ultimate 12 to 24 Volt Automotive Electrical Circuit Tester Kit : Amazon.com : Automotive

Wish this tester was cheaper but I like the fine tip probe and features.

barjeep 03-07-2013 09:41 PM

it sounds like a ground issue to me.

NonRubicon 03-08-2013 12:20 AM

Just because you get voltage on the other end of the cables, doesn't mean the cables can handle the load (current). Battery cables and grounds can be corroded internally. Internal corrosion will increase resistance, thus decreasing current. Jumping a battery pushes additional current/voltage into the system, and can overcome the additional resistance caused by internal corrosion.

Anytime I get a no start, but still have battery voltage, I suspect bad cables/connections. Check and clean all grounds - engine block and chassis. If cleaning the connections and grounds doesn't help, try new cables.

jk'n 03-08-2013 06:39 AM

Maybe the "I jumped it and it started" statement offers a clue. I wonder out loud how jumping it could cause it to start if the problem is deep in the electrical system. I can tell you as a certified master electronics technician that in this situation I rely on my knowledge of voltage drops. Testing a battery under no load for instance using a volt meter will show normal voltage that is why a commercial battery tester will have an internal resistor to place a load on the battery and then internal resistance of the battery can be determined. High internal resistance of a battery indicates either discharged battery or problems internal to the battery. Along the length of a wire the voltage should be constant. If moving the meter further away from the battery the voltage on the wire changes (lower) that indicates a high resistance point on the wire. This happens for instance if a terminal is corroded. The voltage on the wire measures 12 volts and the voltage on the terminal measures measures less means that there is a voltage drop across some resistance that is between the wire and the terminal meaning it is likely corroded. It can be a puzzle but persistence usually pays off.

jfallon83 03-08-2013 07:12 AM

I wanna thank all of you for all the good advice. After doing some research last night, and what several of you have mentioned, I've been leaning toward a ground or resistance issue as well. As soon as I'm off work, I'm going to tackle checking the grounds and for voltage drops downstream.

I'm also told by a shop I called that the starter solenoid can get grounded out on these Jeeps, so I will be checking that as well.

I will also probably take the battery somewhere to get it tested by a pro, though it is a brand new battery. I'm also going to take a look at all the relays and fuses, just to be sure.

I had to ride the motorcycle to work this morning and that is never fun in 30 degree weather.

Again, thanks for all the advice and I will be using it this afternoon. I will keep y'all posted on my progress.

90DesertTanYJ 03-08-2013 08:28 AM

Our YJs have a starter switch as well as a solenoid. The solenoid is on the starter and the switch is mounted on the RS firewall under and slightly right of the battery. All initiating power for the starter runs thru this switch as well as the ignition on power circuits. Never really thought about it but this switch may control the accessory off during cranking as well.

Usually tho when I have a no start issue it is the terminals or wiring. Before replacing anything make sure all these connections are solid and clean as suggested above. If you have OEM wires, it may be time to replace them. You can check them first with a ohmmeter. If you have the cheap replacement terminal ends on your battery cables definitely get better ones or replace the whole wire. They can cause all kinds of issues.

jfallon83 03-10-2013 12:51 PM

Hey guys,

Well, I took y'alls advice and started checking downstream to see if I had a voltage drop anywhere. I didn't have to search long. At some point a previous owner put a cheap wire that wasn't a thick enough gauge going from the battery to the fuse box. It had gone bad, but was still supplying enough power to get a signal with a circuit tester to all the components, but not enough to crank it. The jumper cables forced enough power down that it would allow it to crank.

I went ahead and replaced both of the terminals, and all of the wires running off of the battery including the faulty wire to the fuse box. While I had it out, I went ahead and also replaced the starter switch on the column because it looked a little rough and was a pain to get to.

Problem solved and it cranks up perfect. I wanna think everyone for the good advice. I've heard a lot of people say that there are technicians and then there are part-replacers. When it comes to electrical, I'm a part-replacer and I would probably still be out there hunting or replacing parts without all of y'alls great help.

Thanks a ton.

jk'n 03-10-2013 01:32 PM

Awesome!

jonathan75 03-10-2013 02:41 PM

Good job! Glad you found the problem.

jk'n 03-12-2013 06:17 AM

By the way, shotgunning parts - a procedure that involves just changing out parts until the problem is gone - is a standard in the troubleshooting industry - especially if the parts that you are changing out are not expensive or you have a good supply of new parts and can change them in and out quickly. I replaced the wiring harness on my 92 jeep for the positive terminal pretty much knowing that it was bad but not for certain. In addition I had shotguned the starter and battery just previous and that didn't solve the problem. The combination of the three items being replaced has made for a solidly starting jeep - every time I start it. The repair cost was inconsequential. Had I put it in the shop, the bill would most likely have been just as high and only the bad part would have been replaced......maybe. Even repair shops can make a mistake and shotgun the wrong part ;).


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