Electricity

Electricity has always been my achilles heel when it comes to automotive repair and maintenance. I just don't get it. Nonetheless, my 94 xj has had an issue with the cigarette lighter since the day it was born which was before the advent of cell phones. When they came out on the market all my cigarette lighter could do aside from lighting cigarettes ( I don't smoke) was blow up cell phone chargers and cell phones. With its history I'll be damned if I'm going to throw my Iphone on there to see what happens,...

I do remember at Sears once when I went to get a new battery, the tech plugged a metered device into the cigarette lighter and said that my charging system wasn't working properly.

While it obviously has not been a super important issue to me it would be nice to be able to plug my GPS in without worrying about blowing it up too.

Where do I start and where does the lighter get its power from. The Jeep otherwise has never had any electrical issues.

Pretty odd, right? :confused1

If your charging system (rectifier/regulator) isn't right you may be getting more than 12v at the lighter. Since you aren't blowing fuses or experiencing weird electrical issues it's probably borderline. However cellphones, etc are far less tolerant of voltage fluctuations than vehicle components.
I would start at the alternator - have it checked for proper output.
No insult intended but that kind of comment about the charging system would have had me address it right away.

yardape said:

I do remember at Sears once when I went to get a new battery, the tech plugged a metered device into the cigarette lighter and said that my charging system wasn't working properly.

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I wouldn't trust any kind of testing device that was plugged into a cigarrette lighter. Firstly because it's not on a mains cable from the alternator, and lastly because XJ interiors are wired like crap, there's about 10 reasons in between.

Do you own a multimeter? Can you use it?
http://mechatronics.mech.northwestern.edu/design_ref/tools/multimeter.html

after you've gotten familiar with the meter you need to start checking voltages. Start at the battery with the motor running, you should see between 13 and 14 volts Anything higher than that and the voltage regulator is not working properly. I can't remember if the regulator is in your PCM or not on that year. probably, if that's the case then I would try swapping the alternator, or at least taking it to the parts store to be tested. Their testing machine will regulate the alternator, so if it performs OK there it's a problem in the PCM based regulator. If it doesn't it's an internal alternator issue, replace the alternator.

If the alternator tests out OK and you're getting the proper voltage then you need to move onto the interior wiring. Pull the fuse that powers the lighter socket, probe the fuse terminals with the hot lead of he meter and ground the negative lead to the body. A door hinge bolt is usually handy. You should see nearly the same voltage reading you got at the battery, with the motor running I'd expect no less than 12V at the socket, and preferably about 12.5-13. If you get anything less than you've got a big resistance problem in the positive lead going to the socket.

Next thing to check is the ground going to the socket, set your meter to Ohms. Attach the red wire form your meter to the outer shell of the socket, now ground it to the same chassis ground you used to test the voltage. If it's higher tan say, 50 ohms, you've got a grounding issue.

just think of electricity like water. The alternator is the pump, the battery is a storage tank and the wires are like pipes. Volts is analogous to pressure, and amps is like the flow. You need good enough connections to the socket to handle the volts and amps, just like you need pipes large enough to handle the flow requirements of your home plumbing while maintaining pressure.

It is not likely that your voltage is too high, although that is easy enough to test with a voltmeter. I guess it is possible that your lighter socket is hooked up backwards. You should get 12-14V when hooked up from the inside center lead in the socket to a ground. And no voltage from the outside shell of the socket to ground. This could be easily checked with a test lamp too. Be carefull not to let the lead from the center point touch the outer shell or you will blow the fuse.

If you are not electrically inclined, don't want to do the diagnostics, everything on the jeep works fine, and don't use the lighter for anything other than charging stuff, you could plug a cheap inverter into it and use a wall charger. This will provide a regulated 120 AC volts

BrokenSockets said:

If you are not electrically inclined, don't want to do the diagnostics, everything on the jeep works fine, and don't use the lighter for anything other than charging stuff, you could plug a cheap inverter into it and use a wall charger. This will provide a regulated 120 AC volts

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or even just get an aftermarket 12V socket and rewire it, provided that the rest of your charging system is OK.