One for A/C guru's...

[Scott Douglas]

While removing my UNGO box from my '78 SC, I noticed some wires in the trunk that led over to the driver's side wheel well. Looking in the wheel well, I found a 'nut' with wires attached coming from the trunk.
I looked around today after taking the wheel off so I could see better, and I found a hole in the dryer for the A/C that was covered with tape. The 'nut' has a stud coming off it and low and behold, that stud is the same thread as the hole in the dryer.

As you can see, I've installed the 'nut' in the hole in the dryer. It was pretty obvious from the dirt on both the 'nut' and the tape over the hole in the dryer, that these have been apart for quite some time. My A/C blows cold air, but isn't used much here in SoCal.
Will my putting the 'nut' back in the hole in the dryer affect the running of the A/C?
Can you give me any reason(s) why it would have been left undone?
Thanks for any help here. I just don't want to blow up my A/C system.

[blucille]

does the ac really blow cooler than outside/ambient air? I find this hard to believe......I am confident that's the low-pressure switch for the A/C system, so if the whole thing is removed, you'd lose all the refrigerant, meaning the a/c system won't blow cold air.

I can't imagine who would remove this, if someone diagnosed that the a/c wasn't turning on, and it was because of the low pressure switch, they'd have to evacuate the system in order to swap out the switch.....makes no sense to remove it and tape it up.

[Scott Douglas]

If you look at this tech article: Pelican Technical Article: Air Conditioning Compressor Upgrade

You'll see in picture 5 that that hole is open in the dryer.
There isn't any refrigerant leak when it's open.

[wwest]

Research indicates that the "stud" receiver opening is inclusive to most 911 receiver/dryers. Must be some sort of temperature sensor/switch then.

After more research... According to BEHR that is a mounting accommodation for a their "thermo Fan Switch". Switch apparently used to bring on additional, auxillary, condensor fan speed/capability should the refrigerant in liquid state arriving at the recieevr/dryer be to hot for adequate system performance.

[kuehl]

Scott,

Here is an old thread:
HELP NEED! AC/Dryer Switch See Picture.

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 off the drier would never provide
its intention.

You have original hoses. They leak. 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.

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

[blucille]

Thanks for the education....

[Scott Douglas]

Thanks.
I've read thru your Mr Ice project.
If I were keeping the car I'd consider upgrading/fixing the A/C so it works better than it does.
I just wanted confirmation that putting the switch in the dryer wasn't going to hurt anything and it appears that is the case.

[wwest]

Originally Posted by kuehl

Scott,

Here is an old thread:
HELP NEED! AC/Dryer Switch See Picture.

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....

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

....

[kuehl]

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.

Originally Posted by wwest

....
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.

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.

Originally Posted by wwest

...."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.

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. They leak so many ppm, at a given pressure and temperature. And if you doubt this simply contact Parker or Goodyear's engineers.

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.

Originally Posted by wwest

..
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.

That's not what my sentence above says and I don't recall posting anything concisely as you have twisted. But if you want to twist it Wwest it's gonna hurt ya, lol.

[SilberUrS6]

Originally Posted by kuehl

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

[whistles innocently]

[wwest]

Originally Posted by kuehl

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.

Please re-read post #7, corrected.

...

[kuehl]

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

[wwest]

Originally Posted by kuehl

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

EPA white paper "bested" you.?? Looks so to me, on ALL counts.

[DRACO A5OG]

summer is coming

[fintstone]

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

[wwest]

Originally Posted by fintstone

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.

...

[ClickClickBoom]

Sweet Jeebus,
This thread, like all the other A/C threads devolves to a, my pet turd is cuter than yours, because mine came from a unicorn. News flash if you cannot drive a rear engined car because its too hot outside, borrow your wife's Honda. Roll down the window, it has 2 or more benefits, 1-you an hear the sweet SSI music more clearly, 2-it will help the car be the same as the outside ambient temperature, if that's too hot for your delicate sensibilities, refer back to wife's Honda comment. I usually read all the tech stuff, because I usually learn something, even if its not in my area of interest, but this is way over the top, going back to the Yugo forums, far less drama.
eric

[fintstone]

West
If you recharged every 2 years...you did have a "leak problem"... My R134a system with barrier hoses has never needed recharging.

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."

[wwest]

Originally Posted by fintstone

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."

My refrigerant leak experience was limited to R-12. Both 911s were converted too recently, 2-3 years ago, to make firm judgement, but so far nothing but good news. Plus the C4 is most often driven, but even it is behind our DD, '01 F/awd RX300.

[wwest]

Originally Posted by fintstone

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.

According to Kuehl instead of the cost and effort of replacing the old "non-barrier" hoses your money and/or time might be better spent adding a high side binary pressure switch. In that regard the EPA seems to come down on the side of a "trinary" pressure switch, third switch element to be used to activate additional, auxillary, condensor cooling fans should the system pressure begin to rise to the point of compromsing those hoses, be they barrier or not.

http://www.epa.gov/ozone/title6/609/technicians/retrguid.html