bprusty33

Hi there. I have a 1999 ford explorer and my fiance and I carpool to work everyday. We use his car and my car just sits at home. My explorer had been sitting for two months and then I finally started it. Wouldnt start it was dead. So we jumpstarted my explorer and let it set for 15-20 mins to charge it up. Drove the explorer about 15 miles to our new house and shut the explorer off. Tried starting the car within 5 mins after shutting it off and wouldnt start. Is this an alternator problem or battery problem? Thanks for all your help. Also, somebody told me that a good way to tell if its your battery or alternator is to jump start you car and while its running take your positive lead off of your battery and if it stays running then its not your alternator. Is this true? Thanks.

thefonz

Pulling the battery lead off while the vehicle is running is not a good idea and not the right way to check the alt. Advance,Auto Zone, O'rileys and maybe some others will test charging system and battery for free. Also a volt meter can tell you if your alt. is charging correctly.

batsmyman

Very likely this is a battery issue and not alternator, but if you take it into one of the major car parts places they will run a test and tell you how good the battery is and the state of charge coming from the alternator. The test is easy and only takes a few mins and you dont have to do anything other than pop the hood.

You could try another battery in it (if you have access to one), but a proper test is the best.

PS - Do not pull the battery leads when the car is running - Bad idea.

tony209

This is my favorite topic!

The best way to test to figure out the problem is the battery or the alternator is what you should do as the following:

1. Definitely yes, you can unhook the positive battery terminal to test the battery while the vehicle is running. Why? It will not damage to the alternator or the charging system if you don't drive the vehicle. During the idle of the engine, the charging system don't really produce much current into the battery at all. Moreover, you don't really leave the engine runs for a long time during the testing cycle.
In this case, if you unhook the positive terminal and the engine is still running, you know that the charging system is about to be ok. There is another way to test if you have a DC Volt meter with you: if you have 14v +/- while the engine is running with the battery hook on, you definitely have a good charging system.

2. You said that you could not start the vehicle after you park it for a while, right? When you start it, did the vehicle starter run at all? Can't start or the engine won't run? If your engine spins but won't start up, I'll will tell you how to fix it. Just come back and ask me.

Best regard,

Tony

thefonz

rusty.... looking to risk damaging sensitive electronc parts on your vehicle??? Then follow the underlined advice. Otherwise, have it tested or check the voltage with a volt meter (engine running), should have 13.5-14.5 volts. Less = not a sufficient charge, over 14.5 = overcharging. Of course, this doesn't tell you the condition of your battery or starter.

tony209

thefonz,
Is my underlined advise good or bad?
According to my calculation, the current flows through the circuit of the Explorer while the vehicle is in idle is under 10A, and the current that produces from the altenator while the Explorer is in idle is around 15A. Yet, it's safe if the vehicle is running in idle during the battery test.
During the battery failure, the charger could be damage because the vehicle alternator or the regulator diode is overloaded with the vehicle is under full loaded.

I am sorry that I don't offense anyone idea in this forum, and I am welcome for anyone point out any of my mistaken.

Best regard,

Tony

thefonz

Pulling the battery cable of while the vehicle is running is an 'old school' method, but not recommended on today's vehicles due to sensitive electrical componets. Risk of damage is definately there. A volt meter, as you also suggested, is the better way to go. Especially a cheap meter will suffice and can be had for less than $20.

jester

More than likely, your battery ran down due to the vehicle sitting for an extended period of time without running. The anti-theft system, radio, and other accessories draw a small amount of power all the time and, without running the vehicle or charging the battery the draw will eventually drain the battery. If you are going to let the vehicle sit for very long without driving, I would recommend buying an on-board battery charger (Wal-Mart or any auto parts store should have them). They are simple to install and you just plug it in and it automatically charges the battery when needed and turns off when battery is fully charged. I have used one on my boat for a long time and it has saved my battery. (Just don't forget to unplug it before you drive the vehicle.)

jwko

Definitely an "old school" method. Can be really hazardous on today's computer controlled vehicles.

tony209

Man, this website is so slow!

Let me make it clear.

Pulling the charging cable off the battery while the vehicle is still running is definitely safe. Why?

The charging circuit has much more currents than what the idle engine needs, and it will not be damaged unless you make the Positive terminal gets short to the chassis of the vehicle.

Remember, we live in a modern time, the solid state is more stable than ever. How long do you think a TV set last compare with a TV 20 years ago?

I used to be a mechanic for 4 years. Now I am working in radio communication engineering.

Best regard,
Tony