voltage regulator
 

I have a question about voltage regulator, a friend of mine has a 95 yj 6cyl, newer altenator, newer battery, needs a boost to start every time but runs fine after someone mentioned to him that it may be the voltage regulator, if so is it external? is it easy to change? any thoughts would be appreciated. Also just had my alternator and battery changed on my xj seems to be "overcharging" it is almost in the red is this something i have to worry about? again thanks for any input.

Re: voltage regulator
 

Maybe there is something drawing the battery down while it is parked. Interior light, satellite radio, etc.

You need to do a "parasitic draw test". When the jeep has run a while. Shut it off and get a multi-meter to check amps in between the positive battery post and positive battery terminal clamp while they are disconnected. There cannot be more than around .05 Amps.

Also check running voltage with a voltmeter between positive and negative, should be between 13.5V and 14.5V, gauges are not always accurate.

I believe all voltage regulators on cars made in the last 10-20 years are internal in the alternator. Try above first.

Re: voltage regulator
 

there is nothing in my friends jeep that should be drawing any power while parked radio is even none functional, we will try your suggestions thanks for the help.

Re: voltage regulator
 

From what you described, the charging system is good because it runs when it is boosted without any problem.

The only things that cause dead batteries by morning are IOD's (ignition off draw) or defective batteries with a bad cell or something similar.

Another easy test would be to check voltage before the jeep is parked while running. If the voltage is above 13.5V, the battery is charging and this means the alternator is working correctly. Then check the voltage while parked, should be around 12.6V for a charged battery. Disconnect the battery overnight or as long as it takes for the jeep not to start normally, then connect the battery in the morning and see if it starts. If the vehicle starts fine, the battery is fine and there is likely a residual draw like a glove box lamp or something, if the jeep does not start and it was parked with a full battery, it could be a bad battery.

Figure out the problem soon! If there is a draw on the battery, you are frying the alternator by having to boost the jeep and charge the battery from scratch every time you drive it. It cooks the alternator to have to charge a dead battery.

Have fun, hope you figure it out.

Jet

Re: voltage regulator
 

thanks for the info it must be a defective battery since it won't turn over even after 10 seconds or even less, the battery is 3 months old so it is a bit suprising but i gues not uncommon .

Re: voltage regulator
 

It will run fine after jumped with all the lights on and stuff?

If so, alternator good.

I'd take the battery to a shop to get charged properly and load tested to be absolutely sure it is pooched before spending another $150. Actually battery should have a warranty if you have the receipt.

Jet

Re: voltage regulator
 

of course he does not have the receipt but he will go buy another battery and see what happens. I think he will be in the same boat in a few months seems to be overcharging, anyways we will see what happens, thanks for the info.

Re: voltage regulator
 

If you have a cheap electrical meter, just check battery voltage at a fast idle, if it is over 14.5 volts you are over charging.