Subject: [928] Cooling cowl for Bosch alternator

I'm in the process of replacing the SEV/Marchal alternator with a Bosch unit. It appears I need a different cooling cowl for the Bosch unit. The cowl I have from the old unit won't fit the Bosch unit, even though the alternator fits fine in all other respects.

Does anybody have a Porsche P/N for the correct cowl?




the issue with all the alternators is they cool by sucking in air from behind the alternator and expelling it out the fan in the front next to the pulley . The exhaust manifold is just a few inches behind the alternator so with out a cover and cooling hose providing air from up behind the headlight in the fender it gets too hot to be happy for very long . Hold on to your receipt for the Bosch , you probably will need it.
Jim Bailey
928 International


OK! Sounds like your learning there. My feeling is that Porsche installed the air pipe to draw air for the outside temperature sensor used by the interior climate control (A/C& heating), that the breathing cooler air for the alternator was secondary. That air hose to the alternator is just not seen on your typical car where the fan is bolted to the water pump.

Here's the specs for my 90':

Alternator label plate info:

BOSH #0120 468 004
14V 40/115A
928 603 011 01

Cowl Part #: 928 603 133 07 Note: The cowl attaches with four studs on a square bolt pattern, bolt pattern is on a 5-7/8" diameter circle. There is also a gasket between the cowl and alternator, as well as a special rubber grommet and clip penetrating the cowl for the wiring harness.



Barry .."That air hose to the alternator is
just not seen on your typical car ...." You just made a very accurate statement , the 928 is not a "typical car" and even with the 78-86 which has a belt driven cooling fan Porsche felt they needed to cool the alternator with clean relatively dry air ducted from up in the fender . In my position , where I talk with many 928 owners everyday , we have learned that the alternator gets cooked if you run it with out the rear cover , and the Audi "replacement" Bosch has no studs on the back to hold a cover and no cover made to fit it but it is less money initially to buy one .

Jim Bailey
928 International

"Chris Ford" writes:


So is this what the assembly should look like in the drivers wheel well ????

 Trying to envisage how this actually helps cool the alternator .......


with the rear cover on the alternator rather than pull hot air off the exhaust manifold area it gets clean dry air from the hose in the area behind the headlight. The plastic splash shield protects the hose.

Jim Bailey
928 International


As Jim has already replied, it provides a source of cool, mostly dry, air for the alternator to suck in. But also that collar (and the white wire shown) just before the hose does a U turn is the outside temperature sensor for the automatic HVAC system. The inside sensor is
the funny "vent" in the center console.

David Kelly N4HHE,


I might add that this will likely be the culprit (exterior air sensor being electrically disconnected) when you HVAC system gives you full 'cold' air on the most left position, and anything right of that 'blazing' hot.