Was driving home today in my jeep. On the way home check engine light came on, figured I would drive it home get it checked in the morning.Then about 25 minutes later, the speedometer, the tach, the voltage gauge, and the radio all just died. Gauges bottomed, radio off. I stop and check battery connections etc, looked for bad fuses, but the dome light still worked etc.

Called some backup to come pick me up when it kicks the bucket. About 10 minutes later the lights dim, it starts missing and backfiring through the intake. I loose acceleration and roll off the road. I am almost positive it's the alternator, but I have never had an alternator make the tach and speedo drop. Is that a normal thing for jeeps? Could it be something else?

Also, what is the best way to do a roadside swap on the jeep. I can easily get under it without jacking it up and that's the way I am planning on attempting it. What problems will I run into that I may be better off having her towed? Bringing my socket set, 2 ratchets, a full set of both metric and standard wrenches 1/4 - 1" and 6mm - 20mm ,some wd40 =P, and wire brushes. Will I need anything else that I am unaware of. I'd hate to get there and not be able to do it. It's about an hour drive.

 

Did you have the headlights and/or the blower on when it died in 25min?
You might consider sticking a hot battery in it and driving an hour home. (no headlights, no blower). On my 90 I pull the air-box and the E-fan to get at the PS pump to loosen the belt. No big deal, but I'd rather be at home.

 

My Cherokee recently had a similar problem. Check Gages light came on and voltmeter dropped indicating charging system problem. Rainy night, lights dimming and wipers running very slowly. Almost didn't make it home running on battery. In the last half mile, airbag light flashed. Checked fuses and all good. Took out alternator and had it checked at Advance Auto and it checked out good (nice deal there....they checked it in no time.....no charge). Problem turned out to be the ground connection from the battery negative to the engine compartment 'wall'. The bolt snapped off when I tried to pull it and clean the connection. I drilled a new hole and reconnected and now all is good. Thought I had an alternator problem too. It really only cost me some time to take the alternator off and get it checked. A mechanic friend really convinced me to recheck the vital electrical connections around the battery since corrosion can get bad there.

 

Pull the stored codes using this technique:

http://www.go.jeep-xj.info/HowtoECUcodes.htm

Always nice to know what the OBD system has to say about things. The most common code for a failing alternator is 41.

Replacing the alternator can be done easily roadside. I agree that temporarily installing a fully charged battery is something to consider. It should get you home where you can work on it in the comfort of your own garage.

Good luck.

 

Throw a battery in it and drive it home, never safe to do roadside work, I drive a tow truck and with the lights flashing and flares, people still pass by too close and too fast because they could care less and are careless. At least at home, you will be safe and less stressed to get it done right.

JMHO as Ol"Blue always says...LOL

 

I was already nervous about roadside and the comments you all left didn't help haha. So, I played it safe and bought a new battery to get 'er home with. When I got home I checked the CEL codes(thanks for that link TJ) I had 12, 17, 47, the 55. Nothing I didn't already suspect haha.

I believe there is either a failed fail-safe thermostat, or not one at all in the Jeep. It never gets above 150. Something that I am also fixing while I am already in it replacing the alternator. I checked all grounds and they are solid.