How Can I Tell if My Alternator Is Working?
Transcript is auto-generated.
hi youtubers jeff cote here with pacific outsystems we've got a question from frank frank asks jeff i've been watching your videos about fusing the alternator and you recommend always carrying a spare alternator on board how do you tell when your alternator has blown oh lovely question by the way most of us unfortunately and this is bad assume that things work on our boat and the reality is uh assuming that things work on our boat is probably gonna get us into hot water or trouble so how does one tell if your alternator is working i love that question uh so first thing is an alternator is not this thing that is either on or off that you can just tell it's not that easy it's all about a change and think about a little bit a pool of water uh your alternator is sort of like um it's a pipe feeling a pool of water and your pool is your battery so what happens is you always want to see and this is this is how you do this you you basically look at the voltage at your battery prior to starting your engine so what is your battery voltage it might be 12.5 it might be 13 volts it might be 12 volts but you want to know what your battery voltage is on your engine battery prior to starting your engine when you're going to actually activate your starter obviously the voltage will drop it's going to drop because there's a large load your starter is drawing a lot of amperage so you might draw to 11 volts 10 volts nine and a half volts you're going to see a big drop in voltage but here's the key and this is the key once your engine has started and give it about 30 seconds to one minute and also make sure that you're revving on the rpm so some alternators no output at 800 rpm so you need to be revved up around 1100 rpm but at this point you should see an increase of voltage from where you started so if you started at maybe 12.5 volts and if your alt if your voltage on your battery when your engine is running is 12.3 that means your alternator is not working because what you should have seen is a positive outcome something the voltage should be rising and if it's not rising why not that's because your alternator has failed so your alternator should be rising the battery voltage so if you start and your battery voltage was at 12.5 and now that the engine is running maybe your battery voltage will go up to 13 1 13 3 13 4. or if your alternator is properly sized and it's a pretty big alternator and your battery bank's not all that big like in our cars for example in our cars our car batteries not that big our alternators are pretty significantly they're they're huge compared to the car battery size instantly the battery voltage is going to go to 14 4. but on a boat because our battery banks are really big and our alternators are not all that big it might take time to get to 14.4 volts which is the target voltage of an alternator so what you're looking for is seeing an increase in voltage when your engine starts and that's how you know if your alternator is working thanks for watching
