Any Input Appreciated--sorta long.

This is an electrical problem, and I have not really delved into the electrics of this XJ yet.
What I have done:
Replaced all main wires with 0-gauge welding cable.
Replaced battery 1 year ago.
Replaced alternator 6 months ago (due to strange electrical probs...fixed them).

XJ: 96 country, 4.0 ltr, AW4.

Problems:
1) No reverse lights. Not the bulbs or fuse. I am pretty sure its the NSS and that will be taken off and cleaned and greased tomorrow.

2) This one has been going on for about 3 weeks now. When I first start the Jeep, the volts are at a solid 14 on the gauge. They stay that way for about 30 minutes. Then, while driving in city traffic, they drop to about one needle width below 14. IF I get on the highway at this point, they slowly rise back up to 14 and stay there until I start city driving again.

I cannot figure out if the volts are climbing back up because of the highway rpms? The belt is tight on the alternator (at least I can barely turn the belt 90 degrees on a long run of the belt). The alternator is only 6 months old (new not reman).

ANY help with this would be appreciated!

Thank you

James

No. 1...you are correct about the NSS.
No. 2....sounds normal due to lesser engine speed.

Test the battery with a load test just to be sure. You can use a shop VoltAmpTester (VAT) or do a poor man's one by disconnecting the ignition so it won't start and turn all head lights on and crank the starter for about 90 seconds. Watch the voltmeter (better to have an external digital one) and make sure the battery stays above 9.6 Volts. Remove the fuel pump relay to prevent injectors from flooding engine. With the VAT you can just do the loading from the VAT.

Then when you restart...it should not exceed 15.5 volts. Same if you put an external charger on it. With the voltmeter you can watch the charging voltage of the alternator too. At idle it will probably charge at about 13 to 13.5 volts...higher if battery is discharged.

Yep, I agree. Even though the voltage may show slightly higher at highway speeds, the amps may actually be lower. It's the amperage that overcharges a battery, so if it's relatively cool and not producing excessive gas, I wouldn't worry.....

Thank you for the insightful replies!
Here's an update with a twist.
I replaced the NSS with a new one ($$$). I took the old one off in an attempt to clean and grease it, but the contacts on the arm were really worn down and I dont think they would have worked much longer after the fix. At any rate, the reverse lights now work and all is fine in that little world.

I took the Jeep to parts store and had the alternator tested. It was putting out way too little amps. It was under warranty so I swapped for a new one and installed it tonight.

Volts stay up at 14 mark until one thing I noticed.....
The minute I turn the interior blower moter on, volts drop dramatically! Even on the lowest setting. I can turn on all 3 130 watt daylighters and 2 55 watt rear lights and the needle doesnt move as much.

So my question: what could be wrong with the blower motor? Maybe the dash switch?

Thanks for any further insight guys!

James

Glad you got the other stuff fixed, James.

Unfortunately, that new voltage drop sounds like a shorted blower motor. I don't think a bad switch would cause that much of a current draw.....

Does the switch get hot, or does the blower run very slow...?

the blower motor actually pulls on the electrical system pretty hard even in good shape, especially at full blast. if there were an internal "short" or excessive drag, by way of worn/seized/noisy/etc. bushings or crap built up in there, i'm thinking it could easily pull the volts down like that. i imagine you'd have to pull it to check it out. footnote-my blower at full blast makes more of a dent in my voltmeter than my two 100 watt lights did...

Thank you again!

I will turn my attention to the blower motor next. The controls for the HVAC or the blower do not get hot when used. There is no new noise from the blower than what has always been there. But you never really know I guess until you dig into a situation.

I will keep you posted when I find the culprit. It very well may be that since I had the real "problem" of the bad alternator, I am now just hyper-sensitive to ANY little voltage drop I see and am losing my mind.

I appreciate your attention to my question.

Thank you,

James

The blower motor/voltmeter issue is an old one, and it's almost certainly nothing to do with actual current draw, but to do with the way the whole system is wired. I think if you measure voltage at the battery, you'll find that when the voltmeter in the cluster drops, it's lying. Don't bother digging too deep into this one until you've measured the true battery voltage.

I too have a 96, and last summer when the fan was on high I noticed the voltmeter drop slightly. It wasn't a big drop, just noticeable. I'd have to agree that it has something to do with the way it's wired.

i've always regarded oe gauges as reference points, not as a true measure of whatever's happening. look at your temp/voltmeter readings then pop the hood and check the actual temp at the sender, and check the voltage at the battery with a real meter. pretty big difference.

Thanks guys.
I only have a "sweeping-needle" type multi-meter from Radio Shack... its not digital. Kinda hard sometimes to tell exactly what is going on with it. I'll invest in a digital one and hit the battery directly with it in the next few days.
I'll let you know what is trully going on then.

James

I agree with the above statement from matthew.
Turning on the blower in my 87 results in an instant 2 volt drop on the guage, doesn't matter what setting the blower is on. I suspect that somewhere along the way the guage and the blower share a wire.
Quite frankly, as long as the lights are bright I don't worry about the guage, it's wildly inaccurate and has large fluctuations in response to load. likely because of the inadequacy of the wiring harness.

The reason it drops is because the Battery voltage is measured at the fuse block and not at the battery.
The battery voltage is not really dropping only the voltage on the fuse block.

Okay, update time.

I "piddled" around with a bunch of plug-ends and such yesterday. Took every plug that I could find apart, cleaned the pins up (if there was anything even on them), and applied dielectric grease to them. Pushed them all back together. Then I took all the plugs off of the PCM, cleaned and greased and pushed back together. Checked every fuse that was relevant, replaced a few that "looked" crappy.

Now when I turn on the blower motor, or lights, or A/C, the voltage needle barely moves!!! Yaaaaaayyyy!!

Not sure exactly what I did, or which plug or fuse was the culprit, but all is well for the time being in my "XJ Electrical World".

What I learned? IF having an electrical problem, first check ALL grounds. If that doesnt get it, check obvious things like battery, alternator etc. If that doesnt get it, mess with everything electrical and hope you fix it. (in my case, it worked). If that doesnt get it, come on this board and ask these guru's what to look at next! You guys were great with responses. And the absolute gem about the voltage being measured at the fuse box was wonderful as well as the one about the voltmeter sharing the same wiring system as the blower motor. These, as well as the others were awsome info to have in the future.

Thanks again guys!

James