Alternator Bad?
Thread Starter
Instructor
Joined: Sep 2003
Posts: 169
Likes: 0
From: Lewis Center OH
Alternator Bad?
I had been noticing that my turn signals would slow down when I would brake and when driving at night the lghts would dim when slowed down to a stop. I'm not exactly sure what the correct battery voltage is supposed to be, but it has been running as low as 11.4 and as high as 14 when driving at normal speed. Anyway I decided to stop at Advance Autoparts and have them check the battery and alternator. They said the alternator is showing a bad diaode path. They suggested I take it out and have them bench test it. Should I go throguh the trouble of taking it out or should I trust what they tell me? In addition any hints or information on taking the alternator out? Thanks. 
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
You need to pull it to replace it any way so why not get it tested while its out?
To pull it
Disconnet the bat.
Pull the belt
Remove the bat. wire (The big Red one) from the back of the alt
Disconect the connector
Remove the two bolts that hold the alt. to the motor (One on top one on bottom)
Thats about it It's a 15 min job, just reverse the order to install the new one.
To pull it
Disconnet the bat.
Pull the belt
Remove the bat. wire (The big Red one) from the back of the alt
Disconect the connector
Remove the two bolts that hold the alt. to the motor (One on top one on bottom)
Thats about it It's a 15 min job, just reverse the order to install the new one.
Thread Starter
Instructor
Joined: Sep 2003
Posts: 169
Likes: 0
From: Lewis Center OH
Seems pretty straight forward. The last time I changed an alternator was when I was 16. It was a Chevette. I was trying to get to the Vette part. I finally got there 18 years later. Anyways, you state to pull the belt. How do I go about doing that. Previously I unbolted the alternator and the belt then came off. Is there anything special I should be looking for with the belt. How hard is it to get the belt back on the pulley? Thanks. 
Thread Starter
Instructor
Joined: Sep 2003
Posts: 169
Likes: 0
From: Lewis Center OH
Thanks for the information. I have one last question. Does anyone have an opinion on alternator brand? I looked on Rockauto.com and it gives about 5 options. Oh and one other thing. Speaking of the tensioner, the tensioner makes a knocking sound. I presume may be bad bearings. Should I go ahead an replace it at the same time?
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Replace the tensioner too! I have installed two Delco alternators on my 87 which is driven every day and now has 200k (bought at 36k). Your battery voltage should never get to 11.4 volts. Normal battery voltage is 14.3 volts engine cold, 13.3 volts engine hot. It is normal for the alternator output voltage to drop with increasing temperature.
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