I have a reading of 11.9ish Volts on the alternator of my cavi. The battery still reads a steady 13.55. I thought the reading had to be below 11v before the batt light came on in a car.

Also, i have a "heating up" issue. the serpentine belt is old and worn and im going to replace it, should i just replace the alternator too? or should i wait and see? also, is the lack of engine temp (i just changed the thermostat) related to this or a separate issue entirely? I would think it would have to be separate, but i just dont know...

car has a 2.2L I-4 for those interested.

thnx.

 

ummmm... what you are saying is not possible...

how can the battery read 13.55 volts, but the alternator only read 11.9 volts?

where are you measuring alternator output? what are you using for a ground? are you using the same ground for both tests?

the most a battery will typically see voltage wise is about 12.8 volts without the alternator charging... the only way to get above that is to have the alternator drive current higher, which is why I don't understand how that can be happening...

if I had to guess though, given the battery light is on, and there is obviously still positive voltage coming out of it, would be that the diodes are bad in the alternator...

most places will check for free...

 

Sorry, i mistyped. Batt was at 13.55 with engine off. Alt ran 11.9V for a few mins. This is the first chance i have had to update. I have replaced the alternator. I took it to my local shop to have the test ran and it was pushing on 6.7 volts by the time i got there. it was less than a mile from the shop to my house, so i guess that was enough. I got home turned off the car, put the batt on to charge and took the civic to get a used alt for $50 from a junkyard. Came with a 1 yr warranty tho.

thnx for your help.

 

I second that. It sounds like you may be measuring the battery voltage when it is on a home battery charger. Also, I don't understand how you are measuring the alternator voltage separate than the battery voltage.

The battery voltage with the engine (alternator) not running should be in the 12v-12.8v range. It can't be higher than that (unless you have it on a battery charger or something like that). The alternator (past the diodes that are built-in) outputs pulsating DC. This is smoothed out by the car battery and the voltage of the battery under charge should be in the 13.5v - 14.5 v range.

 

OK LET ME EXPLAIN THIS AGAIN LOL....

I checked the voltage on alt with car running...i got 11.9v. I turned car off, disconnected the battery and checked battery voltage...i got 13.5v.

at any rate, i replaced the alt. and now the light is out.

 

man, I think you need to get that battery checked out too... I've never seen a battery over 13 volts unless it was on a charger or the car was running... nominal voltage for a car battery is 12.6-12.8 volts... above that and something is wrong, below that, and the battery is slightly discharged...

for reference, I see about 30 battery test slips every single day...

 

Ok i will have it checked. My multimeter may be dead too...who knows? its just a cheap one. LOL. I need to get a Fluke, but i dont have the $100+ to part ways with on a tool right now.