i have a 1998 ford explorer my battery volts look low and every time im at a stop light the volts get lower?

Question

and the car shakes do i need a new battery or an alternator

Answer 1

It's probably not a voltage problem. The battery only need to put out 11 volts or so to keep the engine going when the alternator quits. The alternator just quits putting out because the engine is running too slow. It causes your voltage to drop a couple of volts. You need to fix whatever is causing your engine to almost stall.

Answer 2

When you rev up the engine do the volts go back up? If so , the alternator is probably working correctly. Alternator puts out less charge at low RPMs (Its Alternating Current (AC) which depends on the amount of RPMs). The car shaking could be spark plugs that need to be replaced, separate from the voltage problem.

You can take your car to Advance Auto for a free check. Just walk in and tell them you need it checked and they can tell you if the alternator is hosed. A mechanic will probably charge you a nominal fee for the same service, but can give you a more accurate answer.

Answer 3

Actually you said the key word, "shakes"...if your suv is trying to stall at a stop light, one problem is your idle. If your idle is too low, the volts WILL drop off, since an alternator needs a "minimum rpm" to put out correct voltage. This is usually around 800 to 1000 rpm.

Check for vacuum hose leaks, and idle air control valve working properly first. Once you have the vehicles correct idle, not trying to stall, then the volt gage should read about 13 to 14 volts. Amp gages should be on the + side of the middle line at idle. If you still have problems, then take it to an auto parts store and ask them to test the alternator and "load test" the battery.

That should put you in the right direction, I hope so...

Answer 4

the guage in your SUV worrks of the alternator charge voltage but I would check both because a bad alternator causes the battery to drain. also if the battery test good but alternator is bad replace alternator and then charge your batter you should never replace an alternator and run it on a battery that is not fully charge it causes the alternator to work harder and can cause damage

Answer 5

Go to a mechanic, they can put a voltage regulator on and detrmine if it's the battery or th alternator. They usually don't charge for this.

Answer 6

if the volts are getting lower while you at a stop light....Alternator...Remove move it and take it to the Auto Parts store of your choice for testing....I will bet a $100.00 thats the problem

Answer 7

a new battery same thing happened 2 me and my dad the battery is fried if that dnt work get an alternator. it could also be both.

Answer 8

it could be either but i'd bet on the alternator. also check the belt and the pulleys. a loose belt could cause this. the shake is from rough running due to low voltage.