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Sat Feb 11, 2017 2:14 pm

Ok, I havent been able to find a definitive answer for this. I converted my 12v generator to an alternator. I didnt buy a kit, I bought an alternator and a used german alternator stand to do the conversion. The hard part came when I went to put the "alternator" belt on. When I was watching a video Joel made awhile back on converting to a alternator it looked like he used the pulley off the old generator, so I did the same. The belt that is supposed to be sized bigger for a alternator was way too big, but the old generator belt fit perfect. Are the pulley sizes the same? I cant find why the generator belt wont fit other than that.
Thanks ~Hunter

Sat Feb 11, 2017 2:56 pm

I see many suppliers list one pulley for both alternator and generator use. http://www.socalautoparts.com/index.php/alt-gen-pulleys-c-1265_1343

Sat Feb 11, 2017 3:18 pm

12 volt generator uses the same pulley as the alternator, the only exception is the 38 amp bus generator with the cast pulley.

Belt widths vary and can make a big difference in where they ride in the pulley, was your new belt skinnier?, did you move all the shims to the outside of the pulley?

Sat Feb 11, 2017 3:26 pm

Just an FYI.... I came across at one point,and I'd love if someone can confirm:

there's 2 sizes of crank pulley as far as I am aware: 172mm and 178mm, and I'm not sure if that makes a difference for your setup... but it is something that can cause cooling problems...

Sat Feb 11, 2017 3:44 pm

The belt was about the same width or wider. With all the shims on the outside of the pulley the new belt sat about a half inch above the pulley. Meaning I could take it off without taking the pulley apart and it wasnt even touching the pulley. Im not sure what size crank pulley I have but it is stock.

Sat Feb 11, 2017 4:14 pm

Does the lower pulley have a big "D" stamped into it?

Sat Feb 11, 2017 4:23 pm

busdaddy wrote: Does the lower pulley have a big "D" stamped into it?
Where would it be located? Near the timing marks or on the front? I will go look.

Sat Feb 11, 2017 7:21 pm

HunterTheBusHunter wrote: busdaddy wrote: Does the lower pulley have a big "D" stamped into it?
Where would it be located? Near the timing marks or on the front? I will go look.
On the rear face between the reinforcement ribs, it's huge, almost an inch tall.

Sat Feb 11, 2017 7:21 pm

HunterTheBusHunter wrote: With all the shims on the outside of the pulley the new belt sat about a half inch above the pulley.

How could that belt be anywhere near the correct size?
Several times, with several different "stock" generator pulleys, and a stock VW "D" crank pulley, I've found that the commonly recommended
11.5 x 912 "alternator" belt was not even close to fitting, no matter how many shims were in between the pulley halves. It was always WAY too
close to the center of the gen/alt pulley and always got pinched between the pulley halves. Yet I hear of so many using that "alternator" belt.
I can only conclude that there are some wildly different alt/gen pulleys out there.

Sun Feb 12, 2017 12:28 pm

I cant pull the pulley off to see. Mainly I was just trying to find out if I was safe sunning the stock gen. pulley on an alternator. If its not too small or too big. But how much can the wrong crank pulley throw everything off?

Sun Feb 12, 2017 1:30 pm

No need to remove anything, the D is visible even with the rear pulley tin or an A/C pulley installed, it's at 11:00 on this photo from the gallery:

The wrong pulley combination can sometimes effect cooling on hot days or on long highway drives, other factors play into that as well like state of tune, timing, oil weight, etc.. , but why not make sure you have all the right stuff just in case?

Sun Feb 12, 2017 1:47 pm

Ohhh I see. I dont have that pulley then. Ill look around for one and replace it. Should that alone make the "alternator" belt fit properly?

Sun Feb 12, 2017 2:18 pm

Hunter - just use the belt that fits correctly.

The belt designated for alternator is a little wider and a little longer, so sits higher between the pulley halves.

Sun Feb 12, 2017 2:56 pm

Hi Hunter.
Prior to this change to the alternator were you able to use the oem/stock length belt? If so, then the variables are possibly not your lower crank pulley. VW has changed the crank pulley a coupe of times but I don't recall a belt dimension change. I know the alt equipped cars are supposed to use the 912mm belt but I have not bought one of those stupid belts in over 20 years. I currently use the standard, easy to obtain, belt from the generic auto parts stores. The size is 15355 (15/32" x 35.5'). I use this belt for nearly all the applications that I run across. The rational is to allow the customer to obtain a belt while on the road if the situation requires a replacement.
Did you know that the 1500/early 1600 cars used the same belt as the dog-house cars with the "D" crank pulley?
The upper pulley is supposed to be the same (gen vs alt). And you have a genuine vw alt stand.
Are you able to verify the source of the upper pulley?
Why not try the generic sized belt as I mentioned with the correct shim pack?
I have actually installed a sheet metal shim under he gen or alt to compensate for a worn belt groove in the lower pulley when owner had a non-anodized alum pulley.
Bill.

Sun Feb 12, 2017 3:15 pm

rockerarm wrote: Hi Hunter.
Prior to this change to the alternator were you able to use the oem/stock length belt? If so, then the variables are possibly not your lower crank pulley. VW has changed the crank pulley a coupe of times but I don't recall a belt dimension change. I know the alt equipped cars are supposed to use the 912mm belt but I have not bought one of those stupid belts in over 20 years. I currently use the standard, easy to obtain, belt from the generic auto parts stores. The size is 15355 (15/32" x 35.5'). I use this belt for nearly all the applications that I run across. The rational is to allow the customer to obtain a belt while on the road if the situation requires a replacement.
Did you know that the 1500/early 1600 cars used the same belt as the dog-house cars with the "D" crank pulley?
The upper pulley is supposed to be the same (gen vs alt). And you have a genuine vw alt stand.
Are you able to verify the source of the upper pulley?
Why not try the generic sized belt as I mentioned with the correct shim pack?
I have actually installed a sheet metal shim under he gen or alt to compensate for a worn belt groove in the lower pulley when owner had a non-anodized alum pulley.
Bill.
Thanks for all the great info from everyone! The upper pulley I have is the og German one off my old generator and I the belt I am running is a Continental 9.5x905 (if that is standard). Ive been driving it but I just want to make sure there isnt something Im doing wrong.

Tue Feb 14, 2017 4:13 pm

The fatter 11.3mm belt was used on alternator equipped cars, cos the alternator/fatfan combo used drew more hp from the motor than previous generator/thinfan. In other words the wider belt is stronger and was used to turn the extra load added by the wider fan and alternator combo - so using a narrow belt might be less reliable under stress.

Can you provide the make and number of the 'alternator' belt that was too long? There is something wrong, and I'd guess it is the belt is not what it should be - 11.xmm x 912mm....

Tue Feb 14, 2017 4:49 pm

Sounds like the OPs engine likes the smaller generator sized belt (9.5x905mm). Which makes sense if he is running a stock 7" crank pulley and the same generator pulley that was on there before. The alternator axis should be in the same location as the generator since the fan will need to be centered in the same spot.

The stock alternator belt was 11.3x912mm as confirmed in this pic of the VW alternator fan belt (with correct VW part number).

I thought I would throw this in there as a reference. I got it from this thread where they were discussing the very same issue:
http://www.thesamba.com/vw/forum/viewtopic.php?t=408315

Wed Feb 15, 2017 1:21 pm

I returned the "alternator" belt that I got from my FLAPS. Not sure what band it was and didnt look at the actual size but its what the computer showed it should take. I didnt even think to double check ](*,) All I remember about it was that was an expensive little bugger, $19.50!! Im using the stock fan from the engine that was sitted with a generator, not sure if thats the fat fan or not.

Wed Feb 15, 2017 4:04 pm

Hi.
Yeah, like I previously stated I use one size belt for gen's and alt's on a type 1 engine. I have even used this belt on an all Berg 1700 that used the alum degree pulley but it may have been before the Berg shop began anodizing them, as the pulley groove wore a bit. I installed a sheetmetal shim between the alt and the stand lifting it up about .030" and this allowed me to use the same belt. The belt I use is the house brand belt from O'Reilly. It costs approx. $5.00 and the name brand Goodyear is close to $20. the size is 7355 or 15355.
The house brand belt I am using is made in Mexico and have had zero issues with it.
Bill.