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How to remove and replace an Alternator

by Ken D for Caddyinfo.com

I had mentioned that I was going to do a write up with some photos on my alternator replacement on my 1994 Cadillac STS. So here it is:
Here are the steps in the exact order that I R&R the alternator with some pics. To start you will need wrenches or sockets. I used 8mm, 10mm and 15mm. These gear wrenches will be your best friend no questions asked. Disconnect your battery negative first! -remove both torque struts. -remove the air filter box -disconnec t the upper rad hose (battery side) and move it up and to the right side of the engine where it is nicely out of the way. NOTE: the factory service manual says to remove the upper trans cooler line but I DID NOT have to remove this. -if you can get the driver’s side cooling fan out then you can get the passenger’s side cooling fan out. I couldn’t get them out so I just removed the two screws that hold them each in and moved them over enough to get some working room. Ideally it would be easier if you can get them out, but I did do this job without taking them out. HINT: if you remove your battery you will have a lot more room to work with on this side -remove the serpentine belt using ˝ breaker bar by releasing tensioner pulley -remove the upper bolt holding the alternator with 15mm socket with small extension -I then went to the rear bolt that hits the manifold and backed it out as far as it would go -I was missing the 4th bolt which is up and under the manifold a little bit. The mechanic who replaced the alternator before must have said ‘FORGET IT’ and never replaced it. You can get to it with a 15mm stubby wrench if required. I have heard that if you can remove both cooling fans out of the car, then you can get to it with a 15mm socket with a medium to long extension. -I couldn’t reach the lower bolt from the top so I removed the AC splash shield (3 bolts using 10mm socket) -remove the access panel (4 bolts 10mm socket) -now I could get to the front lower bolt on the alternator using my 15mm gear wrench. I could not get anything else to fit in there. Snip any plastic ties that are holding the surrounding electrical wires for better access. -once I was able to get this bolt out the alternator loosened up quite nicely -remove the battery charge cable from the back of the alternator and unplug the electrical harness also BEFORE YOU TAKE OUT THE ALTERNATOR, PLACE A PIECE OF CARDBOARD ON THE RAD IN THIS AREA YOU WILL THANK ME THAT YOU DID BECAUSE THE ALTERNATOR WILL BOUNCE OFF THE FINS NO MATTER HOW HARD YOU TRY NOT TO. -Go back to the top and wiggle the bolt that backs into the manifold and your alternator will now drop down. -here‘s a pic with the access panel off looking down from the top. It looks like it’s a large hole, but it’s not -here’s one from below -drop the alternator to the bottom opening, don’t worry it won’t fall through. -snip the plastic tie that holds the electrical harness to the alternator -now twist the alternator around so that the pulley is facing the middle of the car and one of the bolt holes is facing down and it will drop out with a little elbow grease -replace that sucker with one of these -I did not buy ‘new’ but had this ACDELCO completely rebuilt and saved about $300 Cdn over retail by doing this. This is your choice. - reinstall alt same way from bottom and retie harness and any electrical that are loose -the first bolt I mounted it to was the one that backs into the manifold -I then reinforced it by replacing the upper front bolt -then the lower front bolt with your trusty 15mm gear wrench and it is now solid -if you can get to the rear back bolt that can’t be seen, then replace and tighten that one also. I didn’t have one there (previous lazy mechanic) so mine is being held by 3 bolts and it’s tight. -now go replace your air filter box -then put your serpentine belt on -then replace your battery -let’s finish by replacing the cooling fans -replace upper rad hose -torque struts, -AC splash shield -access panel WE’RE DONE! By doing this job myself, I saved about $700 Cdn. Written by Ken D for the website CADDYINFO.COM