Theoretical Question: Bad alternator bearing...how much horsepower loss?

[kawahonda]

I'm sending my alternator out to Totally Auto tomorrow for a rebuild!

I noticed when I removed it, the pulley was hard to turn by hand. I'd consider it "pretty tight"...takes two hands to turn, one to hold the alternator down and the other hand with some good force to spin the pulley.

Does this translate to power loss, and if so, how much?

[Chryco Psycho]

hard to estimate but figure a 5 hp motor can take quite a load on a lawnmower etc

[kawahonda]

Dang, so I shouldn't expect the car to feel any more livelier.

The slight grinding noise will be gone though, and the engine should be very quiet....that's one thing I can expect!

[Brads70]

It's surprising you didn't do in the belt. I'd guess it would get tighter when it gets hot?

[JonH]

I am also surprised you didn't burn up the belt. I used to have a homemade battery charger using a 3.5 hp briggs motor,spinnig a delco alternator. Don't remember the amperage, (maybe 55) but it worked fine. I don't remember ever having it kill the motor while charging the battery in my race car. So alternators on these old cars don't pull too much power. Now if you have a ton of electronics, that would change the equation...

[kawahonda]

Not sure why everyone is freaking out about what I did or did not do. The car was just fine. The sound was just a slight noise at the front, and only hearable when hood was up. It's not like I was driving it around with a devastating noise for the past 6 months. There was no reason to be alarmed. This was just a simple question about alternator resistance...low vs high, and whats the HP trade-off. I didn't mean to come off as I don't know what the F*$# I am doing.

I picked up a car that was stored in a garage for 30 years. Trust me, I'm doing it alright. I have made no mistakes so far and won't ask for forgiveness.

[Brads70]

I didn't think I was freaking out?    Just surprised the belt survived ok! 

[JonH]

I didn't think I was freaking out?    Just surprised the belt survived ok! 

same here...sounded like it was almost frozen up...I think I answered your question also, no you will not feel any difference in HP

chill out dude

[redgum78]

In theory a 120A alternator would use about 2hp at full load.

Even with your bad bearing it would be lucky to be twice that so yes, less than 5 hp most likely.

[HP_Cuda]

Think of it this way, all your accessories can pull down 15HP under full load.

So if its just the alternator probably 5HP or less drag on your motor.