OT auto alternators?

[snowbeard]

ok, while I await my new brain for the 850, I am trying to improve the non-starting of the wife's 93 subaru legacy (which stranded me in the parking lot of the grocery store this weekend, when I was supposed to be going for a ride >:-(

so the battery is shot, they tried to charge it at checker and the machine kicked it off immediately. it had 9.5 volts just sitting there with the car not running and 10.5 with the engine idling. I didn't check the voltages with the old battery and the rpms up high, but with the new battery and old alternator, it kicks out 14V easy at 4000 rpm, so I begin to suspect my alternator isnt' really bad

the question is that while futzing around, I disconnected the leads from the alternator and the car ran great, no eratic idling, going up and down and sounding terribly bogged, then when I plug it back in it sounds like I'm trying to make it pull a semi! so if my alternator is going bad, could it just be the bearings or some such that make it hard for the engine to spin it but still make power?

I'm at a loss here, I think I should replace it so the car will run better, and maybe even longer, but I hate replacing things that don't really need it...

thanks for your patience!! ';-)

 

[earlfor]

I would take the alternator belt off the pulley and try spinning the alternator with my fingers. If the bearings are good, it will spin very easily with two fingers. If they are grinding enough to slow down the engine when its at idle, I doubt you will be able to turn the alternator with both hands.

You can feel bad bearings with two fingers.

Earl

ok, while I await my new brain for the 850, I am trying to improve the non-starting of the wife's 93 subaru legacy (which stranded me in the parking lot of the grocery store this weekend, when I was supposed to be going for a ride >:-(

so the battery is shot, they tried to charge it at checker and the machine kicked it off immediately. it had 9.5 volts just sitting there with the car not running and 10.5 with the engine idling. I didn't check the voltages with the old battery and the rpms up high, but with the new battery and old alternator, it kicks out 14V easy at 4000 rpm, so I begin to suspect my alternator isnt' really bad

the question is that while futzing around, I disconnected the leads from the alternator and the car ran great, no eratic idling, going up and down and sounding terribly bogged, then when I plug it back in it sounds like I'm trying to make it pull a semi! so if my alternator is going bad, could it just be the bearings or some such that make it hard for the engine to spin it but still make power?

I'm at a loss here, I think I should replace it so the car will run better, and maybe even longer, but I hate replacing things that don't really need it...

thanks for your patience!! ';-)

 

[SqDancerLynn1]

You don't need to run the car at 4K to check it It's a different system than the bike. A bad battery can kill the alternator. Take it off & have it checked

 

[snowbeard]

thanks guys, more answers here than at the subie site!! ;-)

 

[focus frenzy]

that is normal!!!

new batteries often are not fully charged.

the drag is just the alternator charging the battery and powering all the electronics.

the more the alternator has to make the more power it takes to drive the alternator.

I have had the belt idler pully fail on my car and when the belt came off the idle jumped to 2000 RPM.

most of the good auto parts places can test your alternator on the car.
they will test diode ripple and output.

 

[Boondocks]

...the question is that while futzing around, I disconnected the leads from the alternator and the car ran great, no eratic idling, going up and down and sounding terribly bogged, then when I plug it back in it sounds like I'm trying to make it pull a semi! so if my alternator is going bad, could it just be the bearings or some such that make it hard for the engine to spin it but still make power?

I'm at a loss here, I think I should replace it so the car will run better, and maybe even longer, but I hate replacing things that don't really need it...

The alternator draws power from the engine in order to make electrical power. A car alternator doesn't use permanent magnets, but induces an adjustable magnetic field in coils. With this method, high alternator output can be produced at low engine speeds, but it isn't free and takes extra power from the engine. This effect may be noticeable when the alternator is electrically disconnected, and then plugged in again.

If bad alternator bearings were causing "bogging", this would happen all the time whether the alternator was plugged in or not. Bearings are probably one of the last things to go bad on an alternator unless the alternator belt was severely overtightened.

Have you ever used an AC generator (alternator). When you first start it up with nothing plugged in, it runs free. When you plug in an electrical load, you can feel the engine momentarily "bog" until it feeds more power to stabilize at the preset RPM to produce 120V. Could this be similar to what you have experienced?

I think that your alternator is probably OK, but you can have it checked if you are not sure. Probably all they will do is check that the electrical output is within standard limits. Be watchful for parts pushers that would love to sell one under any pretext if they feel they can get away with it.

[edit] Leon's (focus frenzy) post wasn't up when I started mine, and he has given you the right answer without all of my verbiage.

 

[snowbeard]

ok, that makes sense. I think I will try freeing it from the belts and checking the bearings, but you make a good point, if they are shot it will bog even disconnected.

then I'll take it to checkers and have them test the alt on the car. THEN, if needed I'll take mine to the LOCAL fellow who can rebuild it in an afternoon for the same price as a reman'd one from checker. always prefer to pay the little guy, and a shop in boulder's gotta suck for rent!!

thanks a ton!! another victory for theGSResources!! :-D

 

[duaneage]

A 5 inch alternator pulley was worth 7 more HP on my Ford small block vs the 2.5 inch one. Lights were dim at red lights though at 7000 rpm the battery was charging just fine.

God how I miss those days. Cheap gas and cheap horsepower.

 

[Clone]

I have had my alternator checked at Idle, by my guy who rebuilds them and starters, He has me turn on everything and checks some connection somewhere. Then shuts it down and removes the belt and give it a spin by hand. He has rebuilt two for me on different vehicles, and told me to go home a couple of times and stop worrying. But, bogging the engine down soesn't sound right, I would suspect you should smell the drive belt burning with that kind of resistance.

 

[dcpower]

alternator test

alternator test

Put a charged battery in the car and test the voltage with the engine running
the voltage should be 14 volts at approx 1100 rpm with no electrical load on; no lights or heater.
If you have to rev real high to get voltage then probably a diode is bad in the rectifier, you will also get a howl or a sound like bad bearings, these alternators are prone to bad diodes.


dcpower
have owned an alternator rebuild shop for 25 years