battery/alternator problems

[TrevorSmith]

On my 98 explorer the battery light is on all the time unless the revs are over 3500 rpm. The battery is brand new, so I assume I need to change my alternator. So I went and got a multi meter and the battery is reading at 11.67 volts. So it is being charged. No matter what I rev it to or how loud I have the stereo at idle it stays at 11.67. But the battery light comes on below 3500 rpm, so something is not right somewhere. Is this something to worry about.

 

[Blee1099]

On my 98 explorer the battery light is on all the time unless the revs are over 3500 rpm. The battery is brand new, so I assume I need to change my alternator. So I went and got a multi meter and the battery is reading at 11.67 volts. So it is being charged. No matter what I rev it to or how loud I have the stereo at idle it stays at 11.67. But the battery light comes on below 3500 rpm, so something is not right somewhere. Is this something to worry about.

11.67 volts? It isn't being charged effeciently. Should read out atleast 12.4 volts if not higher. Get the alternator tested, sounds like its the culprit.

 

[alexefron]

11.67? yeah, thats dead. Check the voltage with the engine running, should be around 14 volts, if not somethings screwed up with the altranator.

 

[gjw02]

The voltage of a lead acid cell is 2.1 Volts. There are 6 cells, so the terminal voltage unloaded and not being charges should be 12.6 volts. I've seen charging systems putting out anywhere between 13.5 and 14 volts. Sounds like your alternator / voltage regulator is not doing its job.

 

[budwich]

It is likely that your alternator has lost a diode or two on its bridge.... in the field diodes ... those used to "energize" the main rectifying ones. As a result, they aren't able to provide enough "umph" to get the unit to fully function. You can usually take them out / off and test them for opens / shorts.

 

[leviathan]

I have a similar problem with my 2001 explorer
battery is not charging. I replaced the alternator still not charging
I've charged the battery with external charger it holds a charge fine reads 12.3-12.6 with volt meter. Yet when truck is running alternator is not functioning. still reads 12.3-12.6 while running. If I leave it running battery gradually goes down till truck stalls and needs boost to start. I've checked all the fuses I can find all good, is there a in line fuse or some thing to check and if so where do I find it?

 

[BIGHVM]

Maybe check your earth cable- I heard some can look good but be rotten inside!

 

[leviathan]

ground is fine
I think the problem is with the circuit that controls the alternator
newer vehicles the alternator does not always run the computer turns it on and off depending on the level of charge in the battery. so it needs a signal from the computer to turn on the alternator I don't think the alternator is getting a signal. but i can't find the source the signal wire to the alternator goes under the power steering pump and i can't find where it comes out. from what i've read there is supposed to be an in line fuse but i can't find it.

 

[budwich]

I don't think your "computer turns on the alternator" is true... at least in 2001. Normal alternators have two connections, one for the "main voltage" and one for "reference". It would appear the reference voltage isn't there. Having said that, you should see a warning light come on from "improper operations / levels". NOTE: there is usually never a "direct" connection to battery from the alternator, it usually goes to somewhere "near" the starter either the starter itself or the starter relay..... check those connections.


Having said the above, IF your circuit is computer controlled (I only have 96 drawings), then you should see three connections referred to A, B and I. As indicated A and B should be measuring some form of ~12v while I is sent from the PCM and is a lower voltage signal (~8-9).

 

[leviathan]

yes i am getting battery voltage at the alternator on the main connection but there is no increase in voltage when the engine is started reads about 12.3-12.6 volts with a fully charged battery and does not change whether the engine is running or not. the other alternator connection has 3 wires going to it and i can get any voltage reading on any of those wires. the battery light does come on when the engine is running but i get no signal or reference voltage going to the alternator. where does the signal come from? is there a fusible link hidden somewhere? can i bypass it by running a new wire straight from the battery or could it be a computer problem?

 

[jls1znv9999]

Have your Serpentine belt checked out. its like $19 bucks for a new one. Cheaper than battery or alternator!

 

[budwich]

There are fuses in the main distribution box for the "reference / sense" voltage.... so check there.