Fan/Alt housing issue

jhelgesen · 09-20-2006, 09:27 AM

Checking my fan belt today and see that my fan is rubbing the housing again.

I start taking things apart and see that the bolts holding my alt together are loose. I can move the front half, shaft, and coil section up and down in my hands.

I am using a rebuilt bosche alternator, and it looks like maybe they used the wrong bolts to hold it together. I can't get a 10mm wrench around the head to tighten it. I figure I'll have to pull it completly out to tighten it back up.

Question is, do I really need the pastic air deflector behind the alternator? The lock nuts go on the end of the bolts, and there isn't enough thread to get another nut on. If I leave it out, I can get the alt retaining nuts on more securely.

jhelgesen · 09-20-2006, 10:24 AM

Is the rear half of an alternator supposed to be threaded where the bolts go through, or is the nut supposed to hold the alt together?

Craig · 10:45 AM

Hi John,

I recently replaced my alternator, and it was tightly held together by the bolts before I did any mounting to the fan housing. Something does not seem right if the alternator can come apart while the alternator is sitting by itself. If it is a recent purchase, I would take it back and show them the problem
Good Luck,
Craig

edit
I would try to use the plastic defelctor again. This is where your wires for the alternator feed through to the alternator. Think they would be buffeted by a lot of air from the fan without it.

304065 · 09-20-2006, 11:06 AM

Those are the wrong bolts holding the alternator together. Alternators are held together by studs, not by separate bolts. Get a different alternator, and if that was rebuilt, use a different rebuilder.

The air deflector is required to ensure proper cooling of the cylinders. Removing it will result in hot spots and premature engine wear.

jhelgesen · 09-20-2006, 11:11 AM

Thanks for the info guys. The rebuilt alt was purchased years and years ago, don't even know from who, but it was in a bosch box. I've found some longer socket head cap screws at Mcmaster that I'll get on order today, then I can put a lock nut on the back of the alt, then the air deflector and another nut.

Wil Ferch · 09-20-2006, 11:20 AM

I'm confused..look at my tutorial here-->

http://www.pelicanparts.com/techarticles/911_volt_reg_replace/911_volt_reg_replace.htm

although it applies to the 84-89 series of alternators. Seems there are 6 bolts ( 3 covered by the air shroud...3 not) that use nylock type nuts. I recall that the nuts allowed a fair amount of stud length to protrude past the nut height...not like the pic shown....)

- Wil

cbeers · 09-20-2006, 11:37 AM

I agree Wil, here is a shot showing some of the studs. The nuts are already removed, but you can see the clean threads versus the dirty ones where the stud was exposed after the nut was in place.....

-Chris

Craig · 09-20-2006, 11:44 AM

John,
Just a thought before you order from McMaster, what if you took the alternator to a rebuilder to see if they could replace the studs/bolts with the correct ones?

Craig

jhelgesen · 09-20-2006, 12:05 PM

I can try Craig, but I live in the middle of nowhere. I did see a electric motor place in town the other day, could give them a ring.

jhelgesen · 09-20-2006, 12:13 PM

Anyone have a picture of the alternator out of the fan housing I can use as a reference? I have a 79 sc motor with an external voltage regulator.

jhelgesen · 09-20-2006, 12:27 PM

Guess this is it.

jhelgesen · 09-20-2006, 01:35 PM

This is what was in the car....

It was a very tight fit too.

The only bolts I could find that fit from Mcmaster are 18-8 stainless, hope they will be strong enough.

Wil Ferch · 09-20-2006, 05:06 PM

I wonder if you have the correct alternator..apparently there were a few different kinds ( and different electrical output ratings) with different "depths" around those years....maybe the rebuild is the wrong kind that yields less thread protrusion????

- Wil

jhelgesen · 09-20-2006, 06:40 PM

Don't know if its right or not, all the numbers are wiped off the model number sticker....

cmonref · 09-21-2006, 04:05 AM

As Wil mentioned, different alternators have different depths. The SC alternators are 3/8" "shallower" than the 84-89 Carrera alternators. the fan mounts are dimensioned to fit the correct alternator. (I just bought an aftermarket housing from Vertex and an alternator for my SC. they shipped the Carrera units. When the alternator died in two months, I went thru some misery trying to get them to send me the correct alternator to fit the housing they had sold me.)

When you say: "I can move the front half, shaft, and coil section up and down in my hands", do you mean that the alternator is loose in the mount WHEN THE NUTS ARE TIGHT? If so, I would suspect that the alternator is not fully seated in the mount. That would explain the looseness AND the lack of protrusion of the alternator's bolts thru the housing for you to put the nuts on.

jhelgesen · 09-21-2006, 04:42 AM

The bolts in the alt are 100mm long, with 28mm sticking out the back side of the alt mounting flange.

The movement of the front half of the alt is from the bolts not being tight through the alt halves. I have some longer bolts on the way that I put some loctite on when installed through the rear half.

Still considering ordering another alt....

Anyone have a dead alt that has the correct studs I can have?

jhelgesen · 09-24-2006, 04:06 PM

Longer bolts are in. Had to cut 3 slot out of air guide so 3 nuts hole alt in place, 3 hold air guide. Didn't like the plastic on all 6 nuts holding in alt. All back together and holding in place, so far. Put some marker lines on the fan shroud to watch for rubbing again.

DohertyCM · DohertyCM's Garage

I just did mine and I thought I would share what I did and found out.

the alternator cone on the back, I did the same thing you did, 3 nuts hold the alternator on and 3 hold the cone and the alternator. Great set up and it actually helps the install process.
I got this from you after you asked the question, and now I find out you are doing the same thing I am now.

The fan shroud band...if you tighten this too tight it will distort the fan shroud. Just tighten enough to hold it in place tightly. Do not gut wrench the bolt. You will end up cracking the fan housing after it becomes distorded.

If you still have it out you should sand down that rub spot with a light grade of sand paper and make it smooth again.
The scraches in the grain can actually cause corrosion and cause a crack.

Just my nickels worth of info.