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Fri May 27, 2011 7:21 am

I put a new generator into my car in October. All things considered it went fairly smoothly.

However I had the generator shaft rechased as the threads were not right and I could not get either the fan nut or the pulley nut to thread onto the shaft.

Recently the fan belt has been getting loose, I will tighten it and a few days later it will be loose again. A few days ago I fired up the car and it sounds awful. Turn it off and find the generator pulley is wobbling around.

I've been busy stripping the car to OG paint so haven't had a chance to look at the pulley until this morning, here is what I found:

The slot for the woodruff key on the back half of the pulley is no longer straight.

The front half of the pulley has those angular shapes cut into it now. The edges used to be straight. For reference it was a bugpack spin-tru pulley.

One of my pulley shims (the outer most one) now looks like an oval.

So what's the problem? Did I buy a bad generator with a warped shaft?
Or is it simply a bad pulley?
Alternatively I had a hard time getting the woodruff key to seat into both the generator shaft and the back half of the pulley. Could this be the problem?

Or did I just f*ck things up when I put it all together the first time?

Thanks for the help
-Paul

Fri May 27, 2011 11:30 am

Junk pulley, plus you might not have got it tight enough at some point.

Fri May 27, 2011 11:35 am

git A new pulley, new woodruff key, and replace any damaged shims(you need 10 total) and git it all Tight!! so it cant walk back and forth..

Fri May 27, 2011 11:41 am

I think you should first get a new pulley and some new shims to replace those ruined. Get a new belt also and start over.
Looks to me like the belt was incorrectly installed in the first place & the two halves of the pulley weren't in paralled to each other causing a wobble that ate up your pulley & shims. (Been there, done that)
It's easy to tighten the pulley halves onto the belt itself, then believe it's tight. Wrong; the pulley halves are tightened to each other, then the pulley rides inside it to various depths depending on the number of shims.
Easiest way I know of to get the correct number of shims is to put the pulley halves together w/ the belt on using ALL the shims available between the two halves. After it's tightened, the belt should be really loose (but at least the pulley's not riding on the belt) Next, take 2 shims away & put them on the outside where they're normally stored under the nut & retighten. Still too loose? Take away another two. Too tight now? Replace one... You'll eventually get it perfect.
I've messed up by guessing w/ new belts & end up pinching the belt between the pulley halves. You'd be surprised how much "smaller" that new belt seems to be before it stretches.
Of course, I could be full of crap & your alt shaft may be bent somehow. See if you can get a coupler & thread a longer piece of pipe to the end of it & give it a spin (with the outer pulley half removed). If it's bent, the elongated shaft will magnify the problem so it's easy to see.

Fri May 27, 2011 11:49 am

Went ahead and ordered a new german pulley, new shims, and a new woodruff key

Will try it all again.

The way I've been doing the belt is:
1) Take pulley front half off
2) Put in nearly all of the shims
3) Tighten
4) Pull out a shim or two
5) Tighten again and keep taking out shims til its all tight

May have tightened the pulley onto the belt at some point in time...a lot of belt dust when I took it apart today :?

Fri May 27, 2011 1:14 pm

how i do it is to use A screwdriver to stop the pulley from terning well I tighten the nut,, Then as it gits tight I pull the screwdriver out and let the pulley turn 2-3 times, then put it back and tighten some more, repeat tell tight.. this allows the belt to ride up the pulley and keeps the belt from being pinched in the pulley

Fri May 27, 2011 1:45 pm

vw_hank wrote: how i do it is to use A screwdriver to stop the pulley from terning well I tighten the nut,, Then as it gits tight I pull the screwdriver out and let the pulley turn 2-3 times, then put it back and tighten some more, repeat tell tight.. this allows the belt to ride up the pulley and keeps the belt from being pinched in the pulley

I used to do it that way until I "thought" it was tight but the pulley had just tightened onto the belt, pinching it... sure thought it was tight. If you're pretty close with the shims, it'll work okay your way & the belt will ride up the pulley. For some reason, my new belt was "shorter" & not in the ballpark shim-wise (manu defect?) so starting out with what I thought was the right amount of shims really messed me up. From now on, I'm starting out w/ enough shims installed to make the belt really floppy, then "creeping" up on the right number of shims gradually.
I read on another forum that Continental was slightly changing the dimensions of their belts to make them "conform" worldwide (whatever that means).... their belts are now slightly smaller lengthwise... meaning a radical change in the use of shims when switching to a new belt...

Here's a nice reference for belt sizes taken from the pre '67 VW forum:

Belt Size
The fan belt used by VW has evolved over the years. They used the 9.5 x 900mm V belt for their 6-volt engines. The Continental 9.5 x 905mm V belt was later used on the newer 12v generator engines. Continental later standardized their belts to a 10 x 900mm (111-905-137B) and 10 x 905mm (OEM 111-903-137D) belt and VW came out with new OEM numbers to reflect this change.

Earlier bugs had smaller belt which was sufficient for the demands of their low wattage generators and smaller fans of their time. The 36hp engine had a fan with 24 blades and a 160 watt generator. The 40hp and 1300/1500/1600cc single-port engines had fans with 28 blades which increases the demand on the fan belt to a small degree. Plus during that time, the generator output rose from 160 watts to 360 watts. As a result, the 1500/1600cc single-port engines had a 5 hp load on the fan belt, whereas the earlier engines only had 4hp. Later, in 1971, the introduction of the doghouse cooler also meant a 5mm wider (10% increase) fan which brought the load on the belt to around 5.5hp. In 1973, the addition of the 220 watt alternator brought the belt load to a whopping 6hp. And with signs of early failures from the thin VW belts, it was time to upgrade the belt size, so the 1973 alternator also got a much thicker heavier duty 11.3 x 912 mm v-belt.

In regards to what belt will work for an engine with an alternator or generator - thicker is better. For the most part, you can run the older thinner belts in a newer engine with an alternator and likewise can run the thicker newer belt in an older engine with a generator. You will just have to add or subtract shims as needed. Properly fitted thicker quality belts should last longer than thinner belts in any VW.

Also note that belts from different manufactures also vary to some degree in true size and different combinations of pulleys and belts can have a surprising impact on belt tightness. The stock pulleys for the generators and alternators are the same, but these pulleys are often replaced with aftermarket ones by previous owners, so you may have to go with a longer or shorter belt to get the perfect fit. Because of this, you may need to experiment with several belts, remember which one works for your auto and remember to buy a spare.

Stock VW 1600 DP with Alternator Belt:
Brand Part Number Size US Conversion Metric Conversion
OEM 111-903-137-E 11.3 x 912mm 0.4448 x 35.9055" 11.3 x 912mm
Gates 7355 13/32" x 36 1/8" 0.4063 x 36.125" 10.3 x 917.6mm
Altrom (NAPA) ATM 11X912
Gatorback (Good Year) 15361 0.438" x 35.500" 0.438" x 35.500" 11.1 x 901.7mm
Dayco 15358 0.44" x 35.75" (36.3" outside circumference 36°) 0.44" x 35.75" 11.2 x 908.1mm
Goodyear 13355
Metric 10X910
Master Pro (O'Reilly) 7355
Master Pro (O'Reilly) 15355
Duralast (AutoZone) 15355 0.438 x 35.500" 0.438 x 35.500" 11.1 x 901.7mm

Euro:
Bosch 1987947500
Continental 11.3-912
Continental 6578116
DIN 11.3X912
Gates Europe N.V. II: 6372
Goodyear 11AV0913
Motorcraft EJD91

The US Gates 7355 v-belt is supposed to fit:
Beetle 1960-1979
Campmobile 1968-1970
Karmann Ghia 1960-1974
Super Beetle 1975-1979
Thing 1973-1974

In case you need to convert inches to and from mm:
mm
inches

Loose Belt
If your belt is too loose with all the shims removed, you may have a one off pulley or worn alternator bearing. A slightly smaller than stock belt is one potential fix. The Gates 7350 (13/32" x 35 5/8") should do the trick.
Brand Part Number Size US Conversion Metric Conversion
Gates 7350 13/32" x 35 5/8" 0.4063 x 35.6250" 10.3 x 904.9mm
Altrom (NAPA) 10X900
Gatorback (Good Year) 15356 0.438" x 35.000" 0.438" x 35.000" 11.1 x 889.0mm
Dayco 15350 0.44" x 35" (35.6" outside circumference 36°) 0.44" x 35" 11.2 x 889mm
Dayco 15355 0.44" x 35.5" (36.1" outside circumference 36°) 0.44" x 35.5" 11.2 x 901.7mm
Goodyear 13351
Metric 10X900
Metric 10X890
Master Pro (O'Reilly) 7350
Master Pro (O'Reilly) 15350
Duralast (AutoZone) 17350 (13AV0890) 1.3cm x 89cm 0.512 x 35.0" 13 x 890mm
Duralast (AutoZone) 17345 (13AV0875) 1.3cm x 87.5cm 0.512 x 34.4" 13 x 875mm

Tight Belt
If your stock sized belt is too tight, the the Gates 7360 at 36 inches (914.4mm) should work for you.
Brand Part Number Size US Conversion Metric Conversion
Gates 7360 13/32" x 36 5/8" 0.4063 x 36.6250" 10.3188 x 930.275mm
Altrom (NAPA) 10X913
Altrom (NAPA) 10X918SET
Altrom (NAPA) 10X920
Gatorback (Good Year) 15366 0.438" x 36.000" 0.438" x 36.000" 11.1 x 914.4mm
Dayco 15360 0.44" x 36 (36.6" outside circumference 36°) 0.44" x 36 11.176 x 914.4mm
Goodyear 13361
Metric 10X915
Master Pro (O'Reilly) 7360
Master Pro (O'Reilly) 15360
Duralast (AutoZone) 17360 (13AV0915) 1.3cm x 91.5cm 0.512 x 36.0" 13 x 915mm
Duralast (AutoZone) 17365 (13AV0925) 1.3cm x 92.5cm 0.512 x 36.4" 13 x 925mm

Continental 9.5 x 905mm for vintage VW diehards

12V Generator Belt
Stock VW 1600 with 12V Generator used a thinner belt (but can still use a thicker one too):
Brand Part Number Size
OEM 1966 to 1973 111-903-137-D 10 x 905 mm
Volvo 973547 9.5 x 905mm
Mercedes 006-997-02-92 10 x 910mm (37 3/4 inch)
Altrom (NAPA) ATM 10X905 10 x 905 mm
EMPI 00-9928-B 9.5 x 905mm

If this is too loose, you can try a 10 x 900mm belt used on the 6V VWs (OEM 111-905-137B)
Brand Part Number Size
OEM 1947-1966 111-905-137B 10 x 900 mm
Altrom (NAPA)
ATM 10X900

Be sure to get a belt which is specific to your powerplant: alternator or generator....
I got stuck with a belt designed for an alternator & quickly found out it wasn't meant to be....