So I took my alternator to a trusted electrical shop. After I installed it the battery light stays on now all the time. When the truck is off, the battery is at 12 volts. When the truck is running the read on the batteries is 14.3. Why would the battery light still be on if it appears to be charging? Thanks!

 

I just did my Alt about a month ago, the light went out as soon as i started the truck back up. You could try taking the cables off the batteries over night, and charge them over night. Are the cables clean?

 

I'd take it back to them and let them know what's happening.

 

Beside the light, 14.3 V is battery cooking voltage and will prematurely damage the battery. Than 12V on the battery after shut down is too low. It should be 12.5-13V. Maybe your battery is going bad, but I would take the whole thing to the shop for proper testing.

 

Really I have heard that 14v is what the alternator should be charging the batteries at, but I could have heard wrong. Any one else have an idea?

 

I'm not so sure about that... EVERY vehicle I've ever seen/checked/used/tested/etc. read 13-14V while running and MAYBE 12V after sitting overnight. Sounds normal to me, but as to why you still have a light, I don't know.

 

A fully charged battery should read around 12.6 V without the engine running, but that will drop as the battery sits. The design average voltage wth the engine running is 13.8 V, but that number can vary depending on load, engine speed and other factors. 14.3 V is on the high side of normal, but not unusual to see.

In any case, the battery light should not be on. I would return the alternator to the rebuilder and have them double check it.

Chris

 

ok so the shop said that they might have put on the ambulance package regulator, which is 110 amps. The non ambulance package is 100 amp. I thought that ours were suppose to be 110 amp. Anyhow they think the wrong regulator is on the alternator. So take it off again and take it in. Yeah.

 

Oh well, its better than frying your batteries.
I had it happened to mine that the battery light came on, I couldn't figure it out but it turned out that the alt. was over charging since the regulator had quit.
The alt died shortly after.