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DIY: Alternator replacement

117K views 103 replies 53 participants last post by  Rob_C 
#1 ·
Hey guys, since I have had to change my alternator 3 times already and with no DIY I thought I'd make my first one.

I am not going to get really specific with material as all you will need is your new alternator and a typical socket/wrench set.

If I were to rate the difficulty of this it would be a 5/10 just mainly because it is a pain in the ass. First timers this can take you a couple hours. I manage to do it in 30 mins now since this was my third time.

First thing to do is to remove the front bumper. I am sure most of you know how to do this. Al you have to do is take all the over prices plastic clips off the top and bottom (if you have any left :laughing: I know I don't.) The buttom of the bumper with have 2 screws on each side of the bumper. Then there is 1 screw on the side of the bumper where it meets the fender on each side.






Then you're going to want to remove your passenger headlight which has 4 10mm bolts to remove. Two on the top, 1 of the side, and 1 under neath which you will need a really long extension for.

Top:




Bottom:


Side:


Then unplug all your light harnesses and remove the light.





Next you will want to loosen the power steering reservoir which is connected to one 10mm bolt.



Next you will want to disconnect the positive terminal on your battery since you will be disconnecting the alternator wire that goes to it. Don't skip this step as I guarantee you will get shocked.



If you want to be extra safe you can use a towel or glove to cover the terminal:



Ok now it is time to get the serpentine belt off which is a PITA if you don't have a long wrench, I had a short one so it took a couple try's. This step is much easier if you have a helper.

First you get a 14mm wrench and place it on the auto tensioner like so:



You're gonna push down as much as you can to get the belt loose enough to slip off the power steering pully and alternator to free the alternator. Do not take the whole belt off as you will not enjoying putting it all back together for no reason.





Time for the alternator, the alternator has 3 bolts, 1 longer one on the top and 2 shorter ones on the bottom.






The 1 bottom bolt to the left is a PITA to get to but don't worry you can do it with some patience. If you need more room just loosen these two 10mm bolts on the passenger and driver side that hold the rad, it doesn't give much but its something.



After you remove the 3 alternator bolts it is time to remove the ground that goes from the alternator to the chasis. Then disconnect the positive terminal attached to the alternator, I believe it is either a 10 or 8mm nut. (my wires looks different because I upgraded the wiring.). Lastly you will need to unplug a green socket that plugs into your alternator regulator.





Now it is time to slide, wiggle n play with that alternator to get it out where the headlight is. The only way I figured to get it out is the have the pulley facing into side giving it just enough space to get it out. Just be patient at this part, it will fit.



 
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#2 ·
After you get it out basically follow these steps in reverse by putting it all back together.









After everything is back together start her up and get out a voltage tester. Ideally you will want your idle to be around 14.3-14.7 volts. Turn on everything electrical and see how low it goes. You should be in the 13's or higher under load at idle. With all that load have a buddy rev the car steady at 2000 rpms and test to see if the voltage jumps back up into the 14's. If you get different values, you probably picked up a bad alternator. First time I switched my alternator it was doing 16-17 volts which messed up the whole car.
:beerchug:

I hope this helps you guys, I am on often so don't hesitate to ask a question or for clarification on something.

:beerchug:
 
#4 ·
No problem :thumbsup:

My guess is the first OEM alt died due to age and my sound system.

Second one I installed was a shitty rebuild which was giving too much voltage messing up my electrical.

I returned that and got another one which basically lasted 2 months passed its warranty. My guess is of course a shitty rebuild and my system.

This one I am :pray:ing it is good as it was rebuilt by bosch.
 
#5 ·
Man 3 times? Fuck that noise.
 
#7 ·
Oh man, just in time with this! My EP alternator just died on me, waiting on AAA to show up right now and digging around to see how bad the install is.
Fucking MASSIVE :thumbsup: for this thread!
Looks like I've got a project this weekend! :laughing:
 
#10 ·
Haha thanks man!
Just hope I don't get a dud unit right outta the box, one headache is enough :noes:
 
#12 ·
Found Denso factory remans at Advance Auto's website. Pricier, and they take longer to get here since they're coming straight from factory, but apparently they're 100% Denso, which sounds like peace of mind to me.
Ordered one, just have to share the wife's Element for a week or so until it gets here.

/411

EDIT:
oh wow, nevermind. Thats not really a great option for you RSX folks.
Denso reman EP3: $260
Denso reman DC5: $475

Damn. Sorry guys.
 
#15 ·
Sooo, how exactly are we normal people supposed to get to the harness connection and the ground connection that are hiding under the intake manifold?
I've been trying to just get an angle where I can get the harness unplugged for 45 minutes now and nothing, WTF? :mad:
 
#17 ·
Goddamn, FINALLY got those connections loose!
Old unit is out, gonna start fresh in the morning and hope reinstalling the new one is a bit smoother :D
One thing I've learned, universal joint FTW; never could have gotten that last bolt that's closest to the middle of the car without one!
Also noticed that the harness is secured to the alternator with a bracket, and then to the engine further down...is that completely necessary you think? That was what made getting those connections so difficult: had no slack in the harness to turn the alternator around and get at them.
 
#18 ·
Told you it is an install about patience :mam:. I forgot what bracket you're talking about but if the harness is not super lose it should be fine. Mine is lose a bit, I probably took it off the first time and forgot about it.
 
#19 ·
Haha no kidding! Got everything back together but the bumper, waiting on that.
Question: since the alternator gave up while I was driving, and the battery (Odyssey PC925) is only showing about 11.4v after being discharged, do I need to top off the battery first, or can I just start her up and let the alternator do its thing?
...cuz I don't have a battery charger :laughing:
 
#21 · (Edited by Moderator)
Just drive around for a few day and see if it gets better. 11.4 is not bad for a car that has been sitting for a bit. It does show the time to change the battery is coming up but that won't be for awhile. My battery gets down to 10v at times and its been like this for 4+ months lol.

Well, had to wait for the wife to get home to jump the car, but everything is running beautifully now.

Thanks again fr the thread/advice! :thumbsup:
No problem glad it all worked out.
 
#20 ·
Well, had to wait for the wife to get home to jump the car, but everything is running beautifully now.

Thanks again fr the thread/advice! :thumbsup:
 
#22 ·
I figured the low voltage was due to the battery being actively drained when the alternator died, plus the two restarts I managed afterwards.
Now that everything is working again, it shows a steady 12.75v like it should. :dontknow:
 
#24 ·
Turned off.
High 13s at idle.
 
#26 ·
Hmm...13.8, wonder if it's low, or just that I'm using the Odyssey instead of an OEM battery.
Or if it was affected by the alternator dying.

The reason I bought the Odyssey was that it is supposed to be a longer-life design than "conventional" ones, would kinda suck if that turned out to be false.
I've chatted with guys that swear by them though. :dontknow:
 
#27 ·
Once your car is on you will only get readings of your alternators voltage, you can unplug the battery when the car is on and it will still run.

13.8 is not bad maybe you had something on you didnt realize.

Have a friend with you to push on the throttle while you get readings do it like this.

First do a reading at idle with everything in the car off.

Then turn everything on and do a reading at idle

Then with everything on have your friend rev the car consistently at 3k rpms and get a reading.

Let me know how it goes.
 
#31 ·
good diy. you didnt have to remove the intake manifold? or is that only if you do the big 3?
 
#34 ·
Hi, sorry for reviving a somewhat old thread, but I have a question about the battery, would it also be okay if i just removed the negative, then positive, then the same on the alternator, along with the plugs? I was reading the diy and I realize yu didn't remove the negative from the battery. Is that more of a personal preference? thanks :]
 
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