I have a 1992 Ford F150. I was told that if you pull the + cable off of the battery when it is running, and it dies your alternator is bad, because if it is good it should still run. Can anyone tell me if this is true
2007-05-22 05:05:11 · 5 answers · asked by thehazymoon 2 in Cars & Transportation ➔ Maintenance & Repairs
Yes and no---if the truck dies, the alt is definitely bad but it might also not be putting out enough volts and amps to run every accessorie and still keep the truck running...best thing is to have it tested for proper output....should be around 14.5 volts. Your battery is there to provide the huge amps needed to start the truck and after it starts, the alternator recharges the battery and provides the power to run the vehicle and all the lights, radio, a/c, heater fan, etc...
2007-05-22 05:17:37 · answer #1 · answered by paul h 7 · 0⤊ 0⤋
First, never pull the positive terminal. In any electrical situation (Household, electronics, etc..) with a negative ground environment, it is best to remove the negative terminal.
All you are doing is isolating the alternator to see if it has enough power to keep the vehicle running without battery assistance.
You really need to do a load test to determine if it is enough volts/amps to operate everything AND properly charge the battery also. (It may only put out enough power only to keep the car running, but nothing else)
Removing the neg. terminal, and turning on all your accessories will do this but...
You risk anywhere from airbag deployment, to a large voltage spike that could destroy the computer. When the charging system sees no battery, it can compensate by a large spike from the alternator..destroying a sensitive computer.
A proper test is needed, but keep in mind that a charging system is closed loop...the output from the alternator is directly controlled by the load placed on the battery. A poor, or old battery will often make the alternator output look bad.
Older cars are ok to do this, but with newer computer controlled ones, it's not recommended.
2007-05-22 06:55:05 · answer #2 · answered by Mechengnr 3 · 0⤊ 0⤋
To an extent it is true, but the best thing to do is take it to a parts store where they do charging system testing for free. Be aware though that if they test the battery and it is already low on charge, the battery will fail the test and they will tell you that you need a new battery when the battery may only need charging.
2007-05-22 05:12:05 · answer #3 · answered by Ron B 6 · 1⤊ 0⤋
It's not a good idea to do this.
On an older car or truck without all these new computers and stuff it wouldn't hurt anything. But on todays computer controlled engines, you're asking for trouble if you do that.
Have it tested at a shop, or somewhere that is able to test it properly.
2007-05-22 05:15:45 · answer #4 · answered by Mr. KnowItAll 7 · 0⤊ 0⤋
That may not be a true test, have it done by a mechanic or Auto Zone, Pep Boys, etc, they will do it for free
2007-05-22 05:13:22 · answer #5 · answered by Anonymous · 0⤊ 0⤋