Sound like a bad battery?

I made a post last night about my battery gauge dropping when the heater was on... http://www.naxja.org/forum/showthread.php?t=28480

Now this evening on my way home, when I would brake, the gauge would go down almost to the red. After I was completely stopped, it would float back up to 13ish.

I noticed my battery has been leaking out the vent. It's about 4 months old, and was replaced at the same time I got a new alternator. Not really just a little leak, but enough to soak up most of the paper tag on it, and eat away at some electrical tape. This is especially worrying since I have my crapuvlights.com headlight harness and relays draping over the top of my battery (the harness isn't long enough to mount the relays...anywhere).

I took the battery to Napa, and had them test it in the vehicle. I just drove up there, and the XJ was turned off when they tested it. The counterman said the battery was "fully charged" and that leaking is "normal". Well, of course it was fully charged... I just shut the car off!!! I started it up and had them see if my alternator was overcharging the battery, which it was not. I have a 100 amp alternator, with 125amp fusibile link in the charging cable.

I should add that my battery gauge has always seemed accurate before (and was).

Does it sound like a bad battery, or possibly something else?

It's a 1990 4.0 AW4

You may have a bad battery, but you may have a battery cable issue instead. When mine acted up like that I replaced the cables with welding leads. I would also replace the battery with a spiral cell batt. like the Optima. My .02

I think that if after experiencing the gauge weirdness your battery is still fully charged, you can probably rule out a charging issue, and if it also cranks all right in the morning you can rule out a battery issue. The problem is more likely to be in the wiring to the accessories and to the gauge. I'd check terminals, plugs, and ground wires.

Another thing you might try is to go for a drive at night. With headlights on, try the various accessories that drop the voltmeter. Do the headlights dim when you step on the brake or crank up the fan? Another quick test for true voltage drop is to turn on the blinkers, then turn on the headlights. Do the blinkers slow down?

If you are getting a real voltage drop, I'd advise a good going over of all major cables. Clean the battery terminals well no matter how clean they look. Don't forget the main battery line that goes to the starter. consider adding another beefy chassis ground too. But if everything is working fine except for the voltmeter, I wouldn't worry much about it.

Mine does the same thing. I've done all the cables with new welding cable, including an extra chassis ground. Also did new alt and Optima red top.
Keith

Alright, this morning the XJ started just fine, as normal. I flipped on my headlights, and bam, gauge drops to 11 - 12 volts. I turned the heater on high, and it hovered around the same area. With the heater off, but headlights on, the gauge went back up to about 13.

I could not recreate a voltage drop under braking this morning (it has only done that at night).

Does it sound like the problem is in the circuit going to the gauge?

I'd check the plugs on back-side of the heater control and fan switch. They tend to get so hot the plugs melt and become a short. Just a thing you may wanna check.

Hey 90, my 96 does the same thing. I even had to replace the heater controll wiring, it was melted. No change. I have replaced the main ground from the bat. with #2 welding cable & still no change. But when checking with a voltmeter I get 14V with no accs. on & 13.6V with the lights & blower motor running. HTH. JIM.

Try cleaning up your grounds, strip off the paint, add oxgard, and reassemble. Do what CraigH wrote up. It will help you situation. You are just suffering from time adding resistance to every ground.

I replied in your other thread, but I'm going to throw this in. If the gauge drops when you turn on your headlights one of two things could be wrong.

1. Your headlight switch is going bad, to much resistance in it.
2. The ground for your headlight circuit might be going bad. Check that ground first, I think it is behind the drivers side headlamp, in the engine bay. Please correct me if I'm wrong.


Alex

Have you put a test meter directly across the battery when the dash gauge reads low? The gauge on my {88 always reads around 11 volts, sometimes less, but when I plug a voltmeter into the cigar lighter it reads in the heart of the green, and a multimeter on the battery reads 14.0 volts.

One common problem with XJs is the ground strap that runs between the cyl head bolt and the firewall...it corrodes at the firewall and causes voltage drops.. take the bolt out and clean the bolt, strap loop and the firewall.