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why does my 3.1 use an alternator for a 3.4?


Guest TurboSedan

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Guest TurboSedan

the last two days i've been trying to get a new alternator for my Cutlass. i went to NAPA first, and asked for an alternator for a '91 Cutlass with a 3.1. that alternator was clocked totally different from mine, and the mounting bolt near the PS pump wasn't tapped like mine. the parts guy and myself thought it must be a fluke so i ordered another. the one that came in today is the same way. i didn't buy it because i doubt my wiring harness would even reach the different plug & '+' terminal location. not only that, since the front mounting hole on the alternator wasn't even tapped, i couldn't even mount it unless i used a backup nut and a longer bolt. however, when i bought this alternator back in 2001, the alternator brace would no longer bolt up, so it may very well be i have been using the wrong alternator since 2001. everything else worked fine except the brace.

 

so they cross referenced mine and found that mine is actually for a 3.4 DOHC Cutlass. the parts guy went and grabbed a new '92 3.4 DOHC alternator and compared it to mine. sure enough it was exactly like mine; it was clocked exactly the same and the front mount hole on the alternator case was tapped like mine is.

 

can someone with a 3.1 post a pic that shows how the alternator is clocked and the plug & '+' terminal location? and can you tell me weather the front mounting hole in the alternator case (near the PS pump) is tapped or not? if it is not tapped, does it use a long bolt with a backup nut?

 

so far i'm thinking i just need to buy another 3.4 alternator :? i am confused.

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Guest TurboSedan

in this pic you can see how the alternator is clocked by looking at location of the plug and '+' terminal. the plug points straight to the front of the car. is this wrong?

 

DSC01374.JPG

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100_0240.jpg

 

physicly it looks different, but theres a pic if anyone wants to make a little drawing off it or somthing

 

(im working on cleaning this forsaken mess up)

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Guest TurboSedan

hmmm appears i have been using the wrong alternator :bash: the plug on mine doesn't seem to be pointed in the same direction as the other pics posted. if someone can give me details about the front mounting bolt that would be great. my guess is it is supposed to use a longer bolt with a backup nut on the other side? IOW the bolt doesn't thread into the alternator case at all?

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Josh,

It looks like your alternator is installed upside down. As can be seen in Prospeeder's pic there should be a brace mounted to the back of the alternator. This brace connects the rear of the alt to a spot on the head I believe.

The two front alt bolts go throught the back of the alternator, and thread into the timing cover. From the looks of your pic the bolt we can see is installed correctly.

You should be able to just rotate your alternator counter clockwise (when looking at the front fan side.) and line up the mounting holes again and you'll be golden.

The plug should face the rear of the car. and the + wire on the alt should be at the bottom of the rear of the alternator, as the brace is bolted to the top rear of the alternator.

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Josh,

It looks like your alternator is installed upside down.

 

Owned.

 

 

:D

:lol:

I didn't really mean it like that, but..... :lol:

 

Well, I laughed as soon as I read it. I think its gonna hit my sig.

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Guest TurboSedan

It looks like your alternator is installed upside down.

 

nah, it can't be installed upside down. it's just not possible to install it upside down because it only mounts one way. it's just clocked wrong because it's for a 3.4 DOHC application.

 

You should be able to just rotate your alternator counter clockwise (when looking at the front fan side.) and line up the mounting holes again and you'll be golden.

 

if i rotated it at all then the mounting holes wouldn't line up. IOW, the front side of the alternator is right, as it can only be installed one way. but the rear side is definately wrong. the front and rear mounting holes are different sizes. the rear hole is MUCH bigger, so simply rotating it is not possible.

 

the case can be re-clocked to make it go on a 3.1 or 3.4... rather easy if you aren't stupid :lol:

 

i need a new one anyway, and i'll be buying one that won't need to be clocked so reclocking the alternator isn't something i need to worry about. i have done that once before a really long time ago though.

 

The two front alt bolts go throught the back of the alternator, and thread into the timing cover. From the looks of your pic the bolt we can see is installed correctly.

 

actually, no alternator bolts thread into the timing cover :?: the front one threads into the alternator bracket, and the rear one does too. there are 3 bolts that thread into the rear cylinder head, but those hold the alternator bracket on. i think you might be misunderstanding which bolt i am talking about? i will get some pics tomarrow when i install the new alternator. the bolt i was using in the front mounting hole definately won't work with the 3.1 'style' alternator, since it isn't long enough to go all the way through the alternator case and bracket...definately not long enough to stick out the other side enough to get a backup nut on it. the shorter bolt i was using worked before, only because it also threaded into the alternator case itself so no backup nut was required.

 

The plug should face the rear of the car. and the + wire on the alt should be at the bottom of the rear of the alternator, as the brace is bolted to the top rear of the alternator.

 

cool, thanks. i'm going to buy a 3.1 alternator tomarrow.

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IMG_6871%20(Medium).jpg

 

And no, the mounting hole near the PS pump is not threaded. There should be a 10mm bolt that goes through from the plenum side, first through the black bracket, then the alt, then threads into the bigger bracket, not the alt itself.

 

The plug wouldn't be on the front side like yours, it'd be on the rear facing the firewall.

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Guest TurboSedan

 

And no, the mounting hole near the PS pump is not threaded. There should be a 10mm bolt that goes through from the plenum side, first through the black bracket, then the alt, then threads into the bigger bracket, not the alt itself.

 

The plug wouldn't be on the front side like yours, it'd be on the rear facing the firewall.

 

thank you so much Tony, that is exactly what i needed to know. i'm going to buy a new 3.1 alternator tomarrow; i just hope the wiring harness can reach far enough. really no reason it shouldn't i guess since i'm using a TGP harness, but when i looked at the 3.1 alternator at NAPA today i had some doubts. it will be nice to finally use the alternator brace again.

 

after i get the new alternator on the car gets dropped off at the exhaust shop!

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FWIW, the alternator was clocked wrong on my 89 Cutlass when I first got it too.

Mine still had that bracket on the rear, but it didn't go to anything.

When it died, I got the proper replacement and then everything lined up.

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