Testing noisy alternator on car
09-23-2007, 03:08 PM
#1
Three Wheelin'
Thread Starter
Testing noisy alternator on car
Hello All,
Trying to diagnose a loud knocking that's gone when the engine is ran with the a/c & alternator belt removed. I replaced the a/c clutch bearing because the alternator is a 3 month old Bosch rebuild thru NAPA, but noise is still there. So before I pull the alternator to return it, I want to try and spin it with the belt while it's on the car using a drill chuck. It spins nice and quiet by hand but I know it needs to spin at 800 rpm to diagnose. Any ideas for me? Will this damage the alt. or anything?
Thanks!
Trying to diagnose a loud knocking that's gone when the engine is ran with the a/c & alternator belt removed. I replaced the a/c clutch bearing because the alternator is a 3 month old Bosch rebuild thru NAPA, but noise is still there. So before I pull the alternator to return it, I want to try and spin it with the belt while it's on the car using a drill chuck. It spins nice and quiet by hand but I know it needs to spin at 800 rpm to diagnose. Any ideas for me? Will this damage the alt. or anything?
Thanks!
Last edited by 951Tom; 09-23-2007 at 04:12 PM.
09-23-2007, 03:23 PM
#2
Rennlist Member
If the alternator is new, and seems to spin without play, then it's unlikely that is the source of the noise, no? I'd get a mechanics stethescope ($10 or so at any parts store) put the belt back on, and pinpoint the source of the noise. Put it on the body of the compressor and alternator -- you should be able to confirm which it is that way.
09-23-2007, 03:50 PM
#3
Three Wheelin'
Thread Starter
I'm thinking the same. The alt. was installed June 2007 and has about 1K miles on it. I guess I got a faulty rebuild? It was a genuine Bosch. I did the screwdriver to the ear trick, but it's too loud with the engine running to be 100% sure. That's why I want to spin it with the engine off.
09-23-2007, 04:09 PM
#4
Three Wheelin'
Thread Starter
I just grabbed the alt. pulley and I can rock it back & forth just a little and hear a faint knock. Is this normal? The new a/c clutch pulley is nice and tight with less play that I can feel. Oh well, at least the repair goes quicker the 2nd time around!
09-23-2007, 06:39 PM
#5
Three Wheelin'
Thread Starter
Ok, to follow up...I looped the belt around the alternator, then around the a/c compressor, and held the belt tight on the end of the drill chuck to drive it....the alt. is silent, yeah! I think my crank pulley is loose.
