2002 QX4 Electrical problem

[gmcdougal]

I went to crank my car the other morning and it turned over 3 times and died. jumping it failed to do anything and the only electronics working were the clock and the security led flashing. sometimes one of the dome lights flashes very faintly. all this lead me to believe i had a bad battery. i took it to the store (battery only 3 months old) and they told me it was dead. they charged it up and ran a test and told me it was OK. i took it home and hooked it up and the same thing....the car acted as if the battery was almost completely dead. i checked the battery by cranking my wifes car with it and checking it with a multimeter (12.71v). i did some troubleshooting and found out that the main battery cable going into the fuse box is only reading 6 volts. My dad recommended i try to hook up jumper cables from the battery to the post in the fuse box to see if i had power through out the vehicle. i tried this and immediately everything inside the car started working. i attempted to crank the car and it fired right up and ran great. Somewhere between where the main cable from the battery that goes down and where it comes back up to the fuse box isnt right. anyone have any ideas as to what this can be? im thinking of just running a short battery cable with round ends from the battery to the post in the fuse box as a temp fix until i can get the problem resolved. thanks

[AZhitman]

Sounds like the cable may have some corrosion inside the insulation. Try disconnecting both ends and checking resistance (continuity) between both ends.

[4xq]

There was a thread recently that involved the fuse box - different problem, but some good pics of the wiring underneath. If you download them you can zoom in to get some close up views.

Thread is here: plastic-burning-smell-from-engine-bay-f ... 93331.html

On your positive battery terminal is a red plastic square connector that has two white / red wires going in to it. Those wires run into the fuse box and power up the vehicle. The other big cable on the positive terminal goes down to the starter.

I think I would try disassembling the positive battery terminal - the red connector will come off - and clean all those connections up. Then retighten everything up. See if that fixes the voltage going to the fuse box.

You could also ohm those wires while you have it disassembled - should bezero ohms to where they connect under the fuse box.

[gmcdougal]

ok, ive done some more testing and have a few questions. the two red/white wires that come off the terminal and into the fuse box read 6.6v each. is this correct? Ive tested these wires as far as i can and they both read 6.6v just as they go into the fuse box. the main battery connection in the fuse box still continues to read 6.6v. i have hot wired a positive to that main connection in the fuse box and the car works exactly as it should. ive ran the car with everything on to put a load on the system and no problems at all. battery reads 14.5v with the car running so the battery is getting charged. im really stumped on this

[greengumby]

ok, ive done some more testing and have a few questions. the two red/white wires that come off the terminal and into the fuse box read 6.6v each. is this correct? Ive tested these wires as far as i can and they both read 6.6v just as they go into the fuse box. the main battery connection in the fuse box still continues to read 6.6v. i have hot wired a positive to that main connection in the fuse box and the car works exactly as it should. ive ran the car with everything on to put a load on the system and no problems at all. battery reads 14.5v with the car running so the battery is getting charged. im really stumped on this

Like AZhitman stated sounds like a bad cable ... you already jumped the cable and everything works fine , replace the main cable at this point may sounds pretty good.

[gmcdougal]

Which cable? The two red/white wires going from the red junction box to the fuse box? Are they suppose to be reading 6.6v each?

[4xq]

Engine off - the red/white wires should be battery voltage. They connect directly to the positive battery terminal and feed battery voltage over to the fuse box.

Engine running - when alternator voltage exceeds battery voltage, current flows from the fuse box through the red/white wires up to the battery. In other words, because charging voltage exceeeds battery voltage, current reverses direction and goes back through the red/white wires to charge the battery. Now you should be seeing alternator voltage on those wires, not 6.6. ( remember if you test for this you need to disconnect your jumper wire you put in or it will may screw up the test).

Your jumper wire is bypassing the red/white wires. You have connected the battery directly to the alternator charging cable which feeds voltage into the fuse box (it is not really the main battery connection as you are thinking it is).

But there is a wrinkle. By creating a new circuit from the alternator charging cable connector over to the battery, you bypassed the 120 amp fusible link which protects the alternator cable from direct shorts to ground. It works, but is not an ideal solution.

There could be internal corrosion of the wires as azhitman suggested, or you could have a problem at the connection on the positive battery terminal. The red square plastic connector will disconnect from the positive battery terminal when you pull the bolt out of it. You can then clean the connections up. While you have the red connector disconnected, you can do an ohms test (between the connector and the fuse box) to be sure the wires are good internally - they probably are, but the test tells you for sure. Those wires are pretty decent sized and should be 0 ohms.

I hope that is somewhat clear - explaining electical circuits is hard to do without diagrams.

[gmcdougal]

Thanks so much for the help. Sounds like I've found my problem. With the vehicle off, I get 6.6v on each of the red/white wires coming out of the junction box. I get 12.70 on the connector going into the junction box.

[gmcdougal]

I've looked everywhere online and cannot find that red fusable link box. Does it exist or am I going to have to splice and make it work?

[4xq]

I took a look at this - hope this helps.

The two red/white wires going into the red connector will unplug. There are no fusible links there - it is just a connector. Heres a link to the wiring diagram: http://www.nicoclub.com/FSM/QX4/2002/EL.pdf Go to page 11. Fusible links are shown by double "s" curves. No fusible links at the battery connection.

That red connector is part of the positive battery terminal - I don't think you can buy it separately. The part number for the positive battery terminal looks like 24345. You can call the dealer and see if I am right about that.

Or, once you figure out how everything unplugs, you might try the pick and pull. Looks like an easy part to snag.