wwest

The evaporator cabin air intake is under the passenger forward floorboard. If you look closely inside that intake you can see the intake "split" for fresh airflow.

Not adjustable insofar as I know.

griffiths

Hmmmm...
Well, actually there are 2 evaporator inlets!
One under the RH floor board and one under the LH floor board on LH drive cars.
And both lead to the evaporator, not outside.
If your 911/930 (up through 1989 non 964) is different please show us your pics.
If 'we' are wrong 'we' will pay for the Becks.
If you want to change your mind you can still pay for the Becks

rusnak

There is a constant flow of fresh air, according to both the owner's manual, and "Porsche 911 Story" by Paul Frere. But it has nothing to do with the AC. So I guess it's impossible to go 100% recirculate, even if you shut the fresh air blower off, there will be passive ventilation, albiet very very slight. The evaporator box has only one inlet, and that comes from underneath the floorboard, either driver or passenger (very clever, Griffiths! hahaha!!) side.

I never knew that faster air travelling over the evap fins would be hotter. I guess it makes sense, but you can't even feel the air unless you're on the second setting. I would really appreciate more air, even if it's not as cold.

UberXY

Mr Grifffith, while we have your attention, would you care to discuss the advantages/disadvantages of converting a system back to R12? I bought a new front condenser from you last week for an '84 which had been converted up to R134a. The shop doing the evacuation and refill says that they think the old stuff cools better and suggested I might have the system back flushed and cleaned and re-oringed and filled with R12. Any thoughts?

BTW R&R'ing the front condenser was a snap.

griffiths

No. Most LH drive 911's and 930's that use the factory Behr system have two intakes, RH and LH side. The RH drives have one in take.

Stick you head out the window and drive at 25 mph, then step on the gas,
are you cooler?

griffiths

The Kuehl Front Condenser is an advantage with either refrigerant.
If you are using R134a the high side pressures start to run higher
as you pass , say, 85F ambient, at which point you may need more condenser.
R12 does cool a bit better however not much better in a 911 and things go down hill in a 930 because the deck lid condenser is smaller.

We all know (or should know; those of us whom drive in ambients above 80F) that the 911 and 930 needs more condenser regardless of the type of refrigerant; other factors such as color of car, cabriolet/tara vs. coupe, number of occupants and relative humidity all place a higher demand on the system).

If you can pull down another 6F or maybe 10F at the vent it might be beneficial to you, it all depends upon the factors noted above, however you have to weigh the costs of R12 vs. R134a and whether your system is "tight" (no refrigerant leaks) as it does not make sense to constantly refill the system.

Also, having the system properly evacuated and charge is critical as well.

rusnak

My dogs seem to think that they are, but what do they know? They're dogs.

griffiths

No comment to the old saying

rusnak

Do receiver/dryers "wear out", and how often should I plan to replace mine?

griffiths

RECEIVER DRIERS

What does a drier do and why must it be replaced: Drier’s are typically used with a/c systems that have expansion valve systems. Systems that use orifice tubes, rather than expansion valves, typically have accumulators. The drier is located in the refrigerant line circuit after the condenser and before the evaporator. The drier contains a desiccant which removes moisture from the system. Driers for use with R134a should have XH-7 or XH-9 type desiccant, both types are compatible with R12 a well. Some studies suggest the use of R134a with a drier containing the older R12 desiccant can result in the break down of the desiccant which would lead to system contamination. The driers performs three functions: (i) Driers remove moisture from the system. Moisture (water) when mixed with R12 refrigerant creates a corrosive acid that will etch holes through the compressor’s reed valves, the condenser and evaporator tubing. Moisture lowers a/c system performance, and moisture will freeze up the expansion valve (internally) causing refrigerant flow and system pressure problems. (ii) Driers help filter contaminants from the system that damage the expansion valve and compressor. (iii) Driers act a reservoir, holding the liquid refrigerant which in reserve for the system. Driers should be replaced when: (a) a system has been opened, recovered or is in need of charging and the condition of the drier cannot be determined, (b) when ever a system shows signs of contamination, moisture, etching or when a compressor locks up, (c) when changing refrigerant types or oil types. Regardless of the time to replace or part cost, investment in a new drier is a smart idea. Many compressor suppliers will not warranty a compressor unless a new drier has been installed.

Other AC FAQ's:
http://www.griffiths.com/achelp/