Originally Posted by kuehl (Post 7402442)

Scott,

Here is an old thread:
http://forums.pelicanparts.com/porsche-911-technical-forum/233032-help-need-ac-dryer-switch-see-picture.html

The drier has a blind hole; female thread.
Blind hole means it has a bottom, not through into the drier,
so no refrigerant will escape.

On some variations of the systems in the 70's there
was this "temperature" switch. I have yet to find the actual
schematic, however normally ac circuits for this type of switch
would either turn off the compressor clutch if the temperature
at the drier got too high, or turn on a the front condenser blower.
Your hose connections, 2 90's at the drier normally indicate
no front condenser, however you might have one, just take a
look underneath the front nose. If you don't have a front condenser
hence no blower up there so the switch would turn off the compressor.
There was never any "speed capability" on the 911/912/930. Front
condenser blower motor speeds (2) came about with the 964.

You could simply follow the wire harness and see where it leads.

If the switch, logically, turns off the compressor when the temps get
too high in the system, then having it ("OPERATED") off the drier (temperature) would never provide its intention.

Sorry miss-read as above....:o

Why do you say that? It seems to me that "excessive" temperature at the drier/dryer might most certainly indicate a need to turn off the compressor, absent other options.

You have original hoses. They leak.

"They leak". But quite possibly ONLY when/if the system goes substantually over-pressure, which is a very distinct possibilty given the unique design, vs other widespread use of this very same hose, of the 911 system.

I'd replace them with barrier hoses and I'd incorporate a low high pressure switch into the hose between the compressor and deck lid condenser.

As Kuehl himself has pointed out in the past, using the binary pressure switch, alone, to control/limit A/C compressor operation, might well alleviate the issue of leakage from the supposed "non-barrier" hoses due tom system over-pressurization.

Lot's of other stuff to consider:
Read the MR. ICE PROJECT

Originally Posted by wwest (Post 7403085)

....
Why do you say that? It seems to me that "excessive" temperature at the drier/dryer might most certainly indicate a need to turn off the compressor, absent other options.

Originally Posted by wwest (Post 7403085)

...."They leak". But quite possibly ONLY when/if the system goes substantually over-pressure, which is a very distinct possibilty given the unique design, vs other widespread use of this very same hose, of the 911 system.

Originally Posted by wwest (Post 7403085)

..
As Kuehl himself has pointed out in the past, using the binary pressure switch, alone, to control/limit A/C compressor operation, might well alleviate the issue of leakage from the supposed "non-barrier" hoses due tom system over-pressurization.

Originally Posted by kuehl (Post 7403233)

Dear fellow-peer PP readers. You know what is going to happen to this thead! lol.

Originally Posted by kuehl (Post 7403233)

Dear fellow-peer PP readers. You know what is going to happen to this thead! lol.

If the switch, logically, turns off the compressor when the temps get
too high in the system, then having it off the drier would never provide
its intention.


Simple. The drier temp switches were designed to cut the circuit when the drier got too hot. Too hot means above ambient. "Leaving it off the drier" means its a good switch connected to the circuit but off the drier. So leaving it off the drier would expose it to ambient which is colder than hot refrigerant, hence it would never cut off the circuit.

You have original hoses. They leak.



Any experienced 911/930 owner and repair shop whom has owned or repaired these cars for a reasonable amount of years knows that the stock non barrier hoses leak.



Yes, but so would the new ones under specific situations...pressure and/or temperature higher than design specifications..??

They leak so many ppm, at a given pressure and temperature.

Yes, but at WHAT pressure and WHAT temperature..or what combination of BOTH?

And if you doubt this simply contact Parker or Goodyear's engineers.

You imply that you have done so, so why not go ahead and tell us??

I'd replace them with barrier hoses and I'd incorporate a low high pressure switch into the hose between the compressor and deck lid condenser.



That's not what my sentence above says and I don't recall posting anything concisely as you have twisted.

Concisely, no. You stated, truthfully, that older systems with a "open to atmosphere" high pressure relief valve could be prevented from actuating when converting to R134a via the use of the binary switch to control the compressor.

But if you want to twist it Wwest it's gonna hurt ya, lol.

Originally Posted by kuehl (Post 7403695)

Waste of time here at this point. Im out of here

Originally Posted by fintstone (Post 7404334)

LOL..


If the old hoses didn't leak, barrier hoses would not have been designed for R134 cars.

First, you should read the EPA engineering white paper in its entirety.

1.) Our leakage problem LONG preceeded the issue of r-134a refrigernat.

2.) While leakage of R-134a through the old R-12 "non-barrier" hoses was at first thought to be a problem it turned out that it wasn't. Quoting the EPA.

In fact, the last study that I saw cited actually claimed 7 times as much loss.

Again, MY '78 Targa A/C and my '88 Carrera needed replenishment of R-12 on the average of every 2 years. If there was widespread leakage (there wasn't) of R-12 why wouldn't someone have developed "barrier" type hoses to solve "our" problem "back when".

"...7 times as much loss..." Again that estimate applies to R-134a...and was eventually proved to be mistaken due to factors other than just the permeability of the hose itself.


While this might be negligible over a few feet if hose in must applications, it us significant when your car has over 40 feet of hose like most 911s.

Barrier hose seems an obvious place to start when upgrading the AC to R134 in these cars.

Or, as Kuehl suggested, when converting to R-134a, also upgrade to the binary pressure switch control to prevent the compressor functioning from ever being the causative factor for system over pressurization, pressurization beyond ~350 PSI.

It makes sense to upgrade to R134 and barrier hose "while you are in there" if you are replacing other parts that require evacuating the system.

No, in the global sense it makes NO sense whatsoever.

Originally Posted by fintstone (Post 7404925)

West
If you recharged every 2 years...you did have a "leak problem"...

My R134a system with barrier hoses has never needed recharging.

Kudos. But would your R-134a conversion experience have been exactly the same with the old R-12 hoses but including a trinary switch used to limit system pressure (***) from exceeding the component design specifications. The EPA engineering white paper seems to imply so.

*** Prevent compressor over-run and activate auxillary condensor cooling whenever, WHENEVER, system pressures climb to high.

Click
Even a Yugo has working A/C. If having defective, non functioning equipment on your 911...or removing equipment because you cannot get it to operate...sounds like a Yugo is exactly what you need. Advice to park a 911 when it is hot out...in favor of a Honda seems rather counterproductive to hearing "sweet SSI music."

Originally Posted by fintstone (Post 7404334)

LOL...

If the old hoses didn't leak, barrier hoses would not have been designed for R134 cars.

The EPA is now on record stating the requirement for the r-134a new hose design was found to be a misguided effort.

In fact, the last study that I saw cited actually claimed 7 times as much loss. While this might be negligible over a few feet if hose in must applications, it us significant when your car has over 40 feet of hose like most 911s. Barrier hose seems an obvious place to start when upgrading the AC to R134 in these cars. It makes sense to upgrade to R134 and barrier hose "while you are in there" if you are replacing other parts that require evacuating the system.