Alternator Remove & Replace

[Westy]

OK, I've read Clarks. My question is, is the procedure the same for my 968? Out thru the top? Mighty tight in there!!!

[Shifter]

Yep. But if you need to just replace the brushes, you don't need to remove the alternator. Usually it is just the brushes that wear out.

[Westy]

I have a new voltage regulator that I can't install because I can't get my paws in there with a screwdriver. I know it's not charging my battery, so I figured just replace all that stuff, seal it up, and have confidence. Are you referring to the brushes on the voltage regulator? I'm 61 and have never opened up an alternator. Really don't know about the innards.

[944 Ecology]

The voltage regulator assembly (including the brushes) are held on with a couple of screws (probably phillips head). Remove the two screws, remove the old regulator, notice the difference in length between the old brushes and the new brushes, install the new regulator, install the two screws.

That's all there is to it, once the alternator is out of the car. (Oh, disconnect the battery before removing the alternator.)

[v2rocket_aka944]

getting to the lower bolt on the alternator is sometimes easier by going thru the driver side wheel well and moving the sway bar drop link out of the way.

[Westy]

I still have the bat wing and skid off the car. Lower access appears to be pretty simple, but thanx.

[thomasryan]

disconnect the negative lead

loosen the AC pivot.

loosen the turnbuckle mounts a half a turn.

mark or measure the length of the turnbuckle and collapse it for belt removal.

pull off the air box lid.

unplug and remove the MAF.

try to flip the angled boot to the throttle and pivot it up on the IAC hose. (you might unplug the throttle position sensor and unclip the anti-icing coolant hose if they are in your way)

you should have another clip for the alt wire at the intermediate bracket between the intake and the motor mount arm.

this should give you a clear view of the regulator. it is white ceramic with the brains covered with a black disc. the brushes are fragile so be gentle on the install. you need to go in on an angle then come up.

spin the alt and listen to the bearings. the rear one was bad on mine but it had a refurbished/reman sticker so crappy bearings. skf bearings are about $20.

if they make a sound, pull it.

13 and either 8 or 10 mm for the alt wiring. look for missing insulation on the loom/harness.

the bolts are long but you only need to slide them forward enough to free the alt.

the alt housing is usually quite tight in the bracket ears.

[Westy]

Nice write-up, Thomas. Thanx.

[Jfrahm]

Thanks! I suspect my 968 alternator is a small source of parasitic drain, does anyone know if this can be measured, like if you pull the wiring off of it and measure the current between the battery cable and the post it was just disconnected from? Or ohm it?

[944 Ecology]

Originally Posted by Jfrahm

Thanks! I suspect my 968 alternator is a small source of parasitic drain, does anyone know if this can be measured, like if you pull the wiring off of it and measure the current between the battery cable and the post it was just disconnected from? Or ohm it?

https://www.amazon.com/Lisle-64970-Parasitic-Drain-Tester/dp/B00RGN5UAY

[djnolan]

Yes, follow the procedure on Clarks. I think 50ma is the minimal draw to keep the DME charged on a 944. A couple of usual suspects you should rule out before concluding it is your alternator would be the window relays (possibly caused by faulty door switch) and any aftermarket stereo or alarm equipment which tends to draw a burst of current when first connected, and then settles down.

Easy to test the door switch, when you shut the car off windows should stay enabled until the driver door is opened. If it stays energized after opening door it will kill your battery.

[thomasryan]

Tesla's ghost is in the glove box light.

The wiring harness can go bad from the alt to the starter. With the car off, see if the exciter wire is hot which would indicate something in the loom.

I wouldn't make or break any connections with the car running/on or jump start for that matter.

There is a small capacitor or noise suppressor that is on the back side in a little black box. If it is bad, you will hear the engine over the radio. Electrolytic capacitors do dry out if someone wants to fix my Bose amps in the W140 beaters.

There is also a 'diode tree' on the stator that changes the AC output to DC. You loose a couple volts of output when one goes bad and get some freaky AC noise on the line.

No clock. No radio. No alarm. No problem.

[Jfrahm]

Thanks, I know the typical stuff for checking parasitic drain and yes the glove box and cabrio trunk and the convenience relay and whatnot. I am actually specifically interested in looking for drain from the alternator.

I had one go bad where the field stayed on with the car shut off but that was pretty obvious and it'd drain the battery in a couple hours. In this case I am hoping for specs and experience.

Re: the OP's issue the regulator is a common problem and they can be finagled out with the alternator in place with a stubby screwdriver Also the cooling hose is important to keeping this part from failing. I have been using Huco regulators lately, some are still made in Germany. The brushes are even pretty easy to replace and can be sourced from Standard or random ebay sellers. This regulator is common among Volvo and Mercedes, etc. If you have a soldering gun just putting brushes in is not hard and the slip rings (which the brushes ride on) are very thick and last a long long time. There are good ebay videos on brush replacement.

Cheers,
-Joel.

[Westy]

UM....Cooling Hose? There was quite a bit of stuff wrong on this car, but there's nothing on the VR that would cool it. Can I source a pic somewhere?

[djnolan]

When i suspected this problem I just had it rebuilt. However since I know the 944 electrical system a lot better now I would want to have hard evidence instead of throwing money at it.

How much is the drain you are seeing? I searched around on the phrase and found a post about a Ford problem. Basically the guy inserted an amp meter and found a 2.5A drain. After pulling all of the fuses and relays and not finding it, he pulled the battery wire off the alternator and it stopped so he concluded it was the alternator, replaced the alternator, and viola. This doesn't provide the why or what in the alternator was wrong, but at least it would be progress.

[Bukowski]

My two cents - modulo 944 NA :

Harbor Freight $5.00 alternator/battery tester is your friend.

Cooling air flow hose - maybe the 968 has this : ask yourself if your engine releases stuff like oil vapor and the like that can get sucked into the nice new alternator before concluding it doesn’t need to go in.

Pay attention to which bolts to undo to save yourself the tensioning. So worth it.

[Jfrahm]

You can see the alternator cooling bonnet in this pic:
http://cdn4.pelicanparts.com/techarticles/Porsche_944_Turbo/54-ELEC-Alternator_Replacement/images_small/pic12.jpg

It's from this writeup:
Porsche 944 Turbo Alternator Replacement (1986-1991) | Pelican Parts DIY Maintenance Article

The cooling air hose is pictured farther down.

-Joel.

[Westy]

Thanx for the links. The articles specifically refer to the 944 and 951 because of the turbo heat. None of this is on my 968. 1) is this stuff still available, 2) Where does the hose connect up font, and 3) I just want to confirm that the 968 DOES use this system.

I know my car was in a minor front end connection, and I've replaced broken stuff, I guess one more thing shouldn't surprise me!!!

[Jfrahm]

There was no turbo heat on the 944NA nor the 944S2. I did not look too far for pics, if there are any, of the ducting on a 968.