eddie_993

Hello to all again!

I recently purchased my 993 and right now, when I turn up the ventilation, the center and passenger side vents don't really put out anything.

The dashboard/defroster, driver's side and footwell vents work fine (I haven't tested the passenger's side footwell). If I turn on the A/C the air gets colder but at this time I'm more concerned about fixing the ventilation.

Few questions:

1) From my knowledge these air cooled 911s never had good ventilation/AC systems so I can't really compare it to my other car. However, even on level 4, the air that comes from the working vents is only medium on a "normal" car. Is this normal?

2) I've read a few threads/articles on the servo flaps but still a bit confused. What do you guys recommend to try to fix the vents? Should I remove the servos, inspect the potentiometer and test them independently using a 12V power source?

Thanks!
Eddie

ToreB

Hi Eddie, welcome as an 993 owner. The ventilation and A/C system is quite sufficient for today's needs, and much better than early 911 models. You describe a typical faulty fresh air and/or mixer servo scenario. I've made a web page that would explain most details on this:
www.porschehvac.bergvill.com
Cheers,
Tore

993 770

Tore, once the servo is an issue, is it erratic or just kaput? I have a similar issue, only the center and passenger vents occasionally have little air flow (still cold air), but then I'll get in one day and fire the car up and all front vents are blowing without any major issue (passenger side center vent has less flow than the drivers side).

Thanks in advance!

ToreB

A failing servo can sometimes start working again, but will certainly fail again. There is no other permanent remedy than to change it. You'll see why on the HVAC detail pages linked above.

A inert mixer and/or fresh air servo will affect the air flow, but this is highly dependant on the temp setting and ambient air temperature. See explanation why on my web page.
Cheers,
Tore

IXLR8

FYI, that may be true of A/C systems prior to the 993, but the A/C in my 993 is ultra cold and far better than the normally functioning A/C in my Honda CR-V.

Its dependent on outside air temperature of course, and where I live it doesn't get that hot (85F and up, recently). If I switch on Max A/C (large snowflake), I better be wearing a fleece 200 jacket.

eddie_993

Hi Tore,

Your site is the one I actually went off of but I needed some clarification. So you're saying in my case it is the fresh air servo and the mixing servos which are actually in the footwells?

Btw the article is great, I'm just not very experienced w/ diy projects.

Thanks again,
Eddie

eddie_993

OK so the A/C will blow very cold, how about the ventilation speed? How is that compared to other cars?

My other car is an Integra and the 993 can only go half as powerful. I've compared it to other cars, as well, and definitely not as strong.

ToreB

Reduced air flow is most often caused by defective servos. With temperature **** set to minimum, all air must come trhough the fresh air flap. With temp set to max, all air must come through the two mixer flaps. If on or more of these flaps are closed due to a servo fault, the air flow will be reduced.

Cheers,
Tore

eddie_993

OK Tore, thanks again.

So if I understand correct, when the temperature is set to the coldest setting, all air will come through the fresh air flap which is the middle one in the trunk. This doesn't affect which vents it comes through, does it?

I'll take a look at this flap later today and see what I find.

Best,
Eddie

ToreB

You are correct Eddie!
Cheers,
Tore