Here's what I'm seeing...possibly alternator?

96 XJ here. Everything seemed ok during a 3 hour drive then when I turn my headlights on during the last 10 min of the trip my tach drops to 0 rpm and my FM radio power cuts out, then back on. Switch my headlights off and my tach comes back on to around 7-800, idle, which is where it should be. Turn the headlights back on and tach goes out again, then when I hit the brakes (brake lights come on, I assume) my speedo drops to 0 as well. This pattern continues as I turn the headlights off and on, cutting out different gauges. Volt gauge reads just a hair above 9 but I'm not sure if this is reliable reading or if it's just pegged to the far left, not working.

This is when I notice the red 'GEN' light to the left of the instrument cluster is on. Never seen it on before but I'm assuming it stands for generator.

Stop and get out to check my headlights and they seem dim.

Course you would know all this goes down when I'm 3 hours away from my garage and tools. So I guess my next step is hopefully to get to a car part store and have the batt. and alt. tested.

Any advice on what this seems like or additional diagnostic steps? Only tools I have with me are some screwdrivers, pliers and an OBD-II code reader.

Thanks

Other than alt and batt I've been told to check my ground connections, but other than the batt neg. pole I'm not sure what to check.

Where should I go checking for a loose ground?

Remove and clean the battery terminals.

Check that your serpentine belt is tight.

Check that the ground connections on the block where the dip stick is mounted are clean and tight.

Check you have water in the battery.

Measure the battery voltage when the engine is running. It should be at least 13.4v at a minimum.

Once you have done these things, take it to Autozone, etc and have them test the charging system or remove your alternator and take it in to have them bench test it.

check and clean the braided ground strap from the back of the head to the firewall.

and the ground located by the dipstick.

those are the two primary grounds for the engine/alternator.

update...

- tried to start for the first time after shutting the engine off but no go. volt gauge was around 10

- serp belt seems a little untight so laid under the front and checked that the alternator wheel was turning, and it was

- batt terminals seemed tight

- ground next to the battery on the fender wall seemed tight, no corrosion. Didn't loosen, clean, and retighten though

- was not able to find the braided cable ground on the block next to the dip stick so wasn't able to check that connection

- OBD II reader shows no codes

- installed new batt from walmart and engine started but volt meter stayed at 11.5 and went down about a half volt when a/c and headlights were turned on. Ran for a while ok but shut off before batt was entirely drained.

Next step is to get a new alternator and put er in and see what happens.

bradleyheathhays said:

Next step is to get a new alternator and put er in and see what happens.

Click to expand...

Pretty sure this will be your issue. Did you try to recharge the previous battery. It may or may not have been totally shot. 10v is beyond dead though, but you never know if they will take a charge or not. Sometimes they will, but you have to kind of coax them into it with the charger on manual.

Just put a new alternator in and everything seems ok now. Messed up thing is there was a piece missing from the new alt where it attaches to the bracket and I'm gonna have to replace it AGAIN. As I'm pressed for time I guess it'll have to do for the short term.

But seeing as I'm gonna have to do this again...are there any specific alternators i should be looking into? I put the only one in listed at Oreiley's for a 96 XJ (Ultima - 90 amp) and I'm just not sure if this one was decent or not. Was in a hurry and had no time to ask or shop around.

Here it is...

http://www.oreillyauto.com/site/c/search...&vi=1180314

Should I be looking for an alt that has a higher output than 90 amp?

Should be fine if you're mostly stock on the electronic side of things.

Look at all you wires coming to your battery. Consider replacing the terminals. They are cheap and it will give you a chance to inspect the wires. I had nearly the same problem and found out the wires are terribly corroded inside the wire. The further I pealed them back the more corrosion I found, to the point of green dust. I saw no signs of exterior corrison. The terminals were the OEM terminals. I noticed an imediate difference on both and 01 and a 99, especially the 99.

bradleyheathhays said:

Just put a new alternator in and everything seems ok now. Messed up thing is there was a piece missing from the new alt where it attaches to the bracket and I'm gonna have to replace it AGAIN. As I'm pressed for time I guess it'll have to do for the short term.



But seeing as I'm gonna have to do this again...are there any specific alternators i should be looking into? I put the only one in listed at Oreiley's for a 96 XJ (Ultima - 90 amp) and I'm just not sure if this one was decent or not. Was in a hurry and had no time to ask or shop around.



Here it is...



http://www.oreillyauto.com/site/c/search...&vi=1180314



Should I be looking for an alt that has a higher output than 90 amp?

Click to expand...

Yep. That 90 amp is plenty, it's probably actually closer to 120 amps under load. Just look at the test sheet that comes with it, last two alternators I got were surprising strong.

You can upgrade if you want but it's a little more involved than just bolting it up. Plenty of XJ owners have done it, I didn't see the benefit for our jeeps.


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