Technical Generator Fiat 850

[fiatmann2000]

850 sport coupe requires a Fiat alternator with double pulley. This alternators new or overhauled cost a fortune (400-500$). Back in the day you could find a company to fix them for small money, but they dont exist anymore.
So to save some money l bought a new Marelli for 100$ with integrated volt regulator an l was thinking l could just swap the pulley and get rid of the volt regulator.

But the axle on the old and new pulley had different dimensions..., the new axle was thicker, so that means that l have to make the hole in the old pulley larger..

 

[bugsymike]

Before you modify parts have you checked to see if your old unit just needed a set of brushes possibly. There are guides on uTube to tell you how, providing it isn't too corroded and comes apart OK. Brushes and rectifiers etc. are often available on eBay.
Another point is some later alternators are for cars where the output is controlled by the ECU.

 

[Gary50]

850 sport coupe requires a Fiat alternator with double pulley. This alternators new or overhauled cost a fortune (400-500$). Back in the day you could find a company to fix them for small money, but they dont exist anymore.
So to save some money l bought a new Marelli for 100$ with integrated volt regulator an l was thinking l could just swap the pulley and get rid of the volt regulator.

But the axle on the old and new pulley had different dimensions..., the new axle was thicker, so that means that l have to make the hole in the old pulley larger..

Hi @fiatmann2000,

I had a similar issue with my 900T about 10 years ago and found a local repairer (long since retired).
There was an issue with the winding's which he fixed but couldn't guarantee as he said it could last forever or 1 week - it lasted 8 days.

I wasn't up to speed with Ebay back then but managed to find an alternative with a bigger output with the same mounting holes through a parts supplier.

Matching the holes was only part of the problem... before you start attempting to make the old pulley holes larger (never a good idea without the correct equipment, due to risk of damage/imbalance).

• Check that the belt alignment is correct - I had to have the replacement mounting flange machined to size as it was 5mm thicker (the belts would have either kept jumping off and/or wear very quickly).
• The supplier managed to supply a double pulley with the new unit but the pulleys were the same size (both slightly smaller that the small pulley on the standard one). This means the gearing is slightly higher (alternator spins faster) however, the water pump spins about the same. If you can get a pulley to fit this is a better/safer option than drilling the old one.
• The fan cowling mount on the water pump arm fouled the new alternator (as larger). I had to file off the cowling mounting which, means I may get issues when needing to replace the water pump in the future.

Overall, it would have been better/cheaper in the long run to locate a same type/size replacement.

Hope this helps.
Cheers
Gary

 

[fiatmann2000]

Before you modify parts have you checked to see if your old unit just needed a set of brushes possibly. There are guides on uTube to tell you how, providing it isn't too corroded and comes apart OK. Brushes and rectifiers etc. are often available on eBay.
Another point is some later alternators are for cars where the output is controlled by the ECU.

Great tips, thx

 

[fiatmann2000]

Hi @fiatmann2000,

I had a similar issue with my 900T about 10 years ago and found a local repairer (long since retired).
There was an issue with the winding's which he fixed but couldn't guarantee as he said it could last forever or 1 week - it lasted 8 days.

I wasn't up to speed with Ebay back then but managed to find an alternative with a bigger output with the same mounting holes through a parts supplier.

Matching the holes was only part of the problem... before you start attempting to make the old pulley holes larger (never a good idea without the correct equipment, due to risk of damage/imbalance).

• Check that the belt alignment is correct - I had to have the replacement mounting flange machined to size as it was 5mm thicker (the belts would have either kept jumping off and/or wear very quickly).
• The supplier managed to supply a double pulley with the new unit but the pulleys were the same size (both slightly smaller that the small pulley on the standard one). This means the gearing is slightly higher (alternator spins faster) however, the water pump spins about the same. If you can get a pulley to fit this is a better/safer option than drilling the old one.
• The fan cowling mount on the water pump arm fouled the new alternator (as larger). I had to file off the cowling mounting which, means I may get issues when needing to replace the water pump in the future.

Overall, it would have been better/cheaper in the long run to locate a same type/size replacement.

Hope this helps.
Cheers
Gary

Great information Gary thx.

 

[fiatmann2000]

I think lve solved it today, l found a older "local" guy that repair generators. So l will rebuild the original generator and that also mean l will keep the external voltage regulator, might change the regulator with a newer one.