AC install

[johann86911]

Hello Porsche guru's.

Okay so I got the car back with running ac.

It's pretty poor with limited cooling and I'm thinking of asking the mechanic to upgrade the whole system.

My issue is that the engine dies when cold when the AC is on. It is also is a bit difficult to start when cold. is this a sign of issues with the cis or does the idle just need to be turned up? or some other alternative?

help please?

[johann86911]

Also - has anybody installed the rennaire system listed by our host on a right hand drive car? are there issues that I need to be aware of prior to purchase?

[Chuck.H]

Did the SC's do anything regarding fuel/timing for A/C? I know on the 3.2's the DME is aware of the A/C compressor running, and on newer cars they go one step further and the engine computer actually controls the compressor themselves, so they can bump timing/idle/etc BEFORE switching on the compressor.

If they don't compensate, you may need to bump your idle yourself to accomodate.

However, reading your posts you seem to have another problem that affects the engine at all times, and the A/C compressor is just the last straw so to speak, and the additional load causes the engine to stall... sounds like you need more cold-start fuel.

HTH,
Chuck.H
'89 TurboLookTarga, 345k miles

[johann86911]

Hi chuck,

Well I suspect it's AC related because if I switch the fan off, it seems to start okay and idle okay as well!

[Scott R]

Originally Posted by Chuck.H

Did the SC's do anything regarding fuel/timing for A/C? I know on the 3.2's the DME is aware of the A/C compressor running, and on newer cars they go one step further and the engine computer actually controls the compressor themselves, so they can bump timing/idle/etc BEFORE switching on the compressor.

If they don't compensate, you may need to bump your idle yourself to accomodate.

However, reading your posts you seem to have another problem that affects the engine at all times, and the A/C compressor is just the last straw so to speak, and the additional load causes the engine to stall... sounds like you need more cold-start fuel.

HTH,
Chuck.H
'89 TurboLookTarga, 345k miles

They did not, however with everything setup correctly it's not a huge drop in rpm's. Normally when they die like to OP is describing it's a mixture issue.

[kuehl]

Originally Posted by johann86911

Hello Porsche guru's.


My issue is that the engine dies when cold when the AC is on.

help please?

If the system is overcharged or if the system pressures get to high that will put a load on the compressor which will load the engine and drop the rpms.

Read the Mr. Ice Project

[johann86911]

Thanks Kuehl.

I guess they've put too much coolant in? I'm guessing having read your article. Given the refrigerant loss over time, does this mean that the RPM etc will return to normal over time? or will I need to take it back to get them to readjust? or reduce the amount of refrigerant?

All this messing around is convincing me to upgrade the entire system. I suppose I should start with barrier hose?

Is that what you would recommend I start with? Or are the losses so small that I would probably get more gains out of a new compressor?

Your advice would be most appreciated.

[kuehl]

"If" was the word.... if the system is overcharged or if the system pressures are too high....

I'd suggest having an independent Porsche shop check your system pressures at idle, deck lid down, windows up, thermostat max cold, fan speed 1 or 2, on a day when the outside (ambient) temp is at least 23C or higher. Your ac tech should be familiar with Pressure and Temperature charts. If the system pressure is too high for the ambient temp at the moment that will give him a clue as what to do next.
Overcharged is simply a more common problem based on the symptom you noted.... rpms drop. There could be other issues but that is where you normally start with the diagnosis.

Yes, a good set of barrier hoses will greatly reduce the most common cause of system leaks. However, if you have the gut feeling you need "some" good upgrades I would suggest you do them all at one time rather than piece meal ala carte the project as that road is always more expensive in the long run. You can do all of the parts replacement/upgrade work yourself and let an experienced AC tech handle the evacuation/charge/test later (its simply not cost effective to buy AC charging and testing equipment if you plan to do this job once & right the first time).

Besides the barrier hoses there probably will be other upgrades you will need. Although historical climate in Melbourne averages 26C this time of year, the trend is upward and if plan to drive inland you will need more cooling capacity.
So it comes down to this: How long do plan to keep the car, How often do you want to drive it, Is comfort critical to the ride. Once again you can do most of the work yourself. So, there are a handful of AC improvement sources out there, in alpha order: Griffiths, Rennaire, Retroaire, and naturally right here on Pelican you can buy some of their products. The choice is up to you.

There are quite a few threads here in the 911 section of the forum discussing what works and what does not work. Off the top of my head I'd suggest reading posts by Jim Sims and mthomas58 , and there are plenty of other good ones.

If you need more help just drop me a PM.

Best regards from this side of the pond,

Griff

[wwest]

Originally Posted by johann86911

Thanks Kuehl.

I guess they've put too much coolant in? I'm guessing having read your article. Given the refrigerant loss over time, does this mean that the RPM etc will return to normal over time? or will I need to take it back to get them to readjust? or reduce the amount of refrigerant?

All this messing around is convincing me to upgrade the entire system. I suppose I should start with barrier hose?

Is that what you would recommend I start with? Or are the losses so small that I would probably get more gains out of a new compressor?

Your advice would be most appreciated.

For a true cold start, the car not having been driven for the previous 3-4 hours or more, A/C head pressure should have no impact, even assuming overcharging, on initial engine starting.

The factory A/C has just one major shortcoming, lack of sufficient condensing capacity. Add two 12 inch fans to force more airflow over/through the rear deck condensor when the engine RPM isn't enough and problem solved.

Oh, sorry, not quite. Add a binary pressure switch to control the compressor to prevent it from producing system over-pressure and/or damaging the compressor should the refrigerant be to low.

Or even better yet use a trinary switch, third element to run the fan, even with engine off, whenever the system pressure is above a preset level.

And don't be overly surprised if this latter effort solves the issue of leakage due to non-barrier hoses.

And please keep in mind, the proof is in the pudding, Kuehl will do, say anything he can to prevent you from trying a $100 solution when he would rather sell you a $1,000 plus solution.

[GaryR]

Originally Posted by wwest

And please keep in mind, the proof is in the pudding, Kuehl will do, say anything he can to prevent you from trying a $100 solution when he would rather sell you a $1,000 plus solution.

It seems to me Kuehl offers up some very good advice for cooling issues here and your shot at him is a tad less than gracious...

[kuehl]

It's OK.
Wwest keeps forgetting to take his meds.

[brads911sc]

WWEST - LOL just LOL.

In some posts he admits they are actually $300 SPAL fans to get what he claims, then in others its $30 SPAL fans. Do a search. Its quite entertaining

He even told a guy that he didnt need to replace leaking hoses but rather install the fans because R134a is so cheap... he actually claims that these SPAL fans solve ALL the shortcomings of the 911 AC system in one post. wow. good to know! LOL

He is the resident guru on so many topics I lost track! yet real science and data proves him wrong over and over on every topic.

he lives in an area where they dont even use AC. stick to the swamp cooler WWEST!

if you want cold AC on a 95 degree day with 85% humidity, ignore anything he tells you. Kuehl on the other hand will deliver what he promises.

Originally Posted by wwest

The factory A/C has just one major shortcoming, lack of sufficient condensing capacity. Add two 12 inch fans to force more airflow over/through the rear deck condensor when the engine RPM isn't enough and problem solved.

And please keep in mind, the proof is in the pudding, Kuehl will do, say anything he can to prevent you from trying a $100 solution when he would rather sell you a $1,000 plus solution.

[wwest]

Originally Posted by brads911sc

WWEST - LOL just LOL.

In some posts he admits they are actually $300 SPAL fans to get what he claims, then in others its $30 SPAL fans. Do a search. Its quite entertaining

Hard to tell the difference between actual SPAL fans at $300 vs "clones" at $30. Possibly even from the very same manufacturing source. Have a look at how COSTCO got it's start, buying up manufacting over production, etc.

He even told a guy that he didnt need to replace leaking hoses but rather install the fans because R134a is so cheap...(***)

Slight misquote, the fans coupled with the trinary switch will probably prevent the over-pressures that otehrwise would overcome, "broach" the O-ring seals.

he actually claims that these SPAL fans solve ALL the shortcomings of the 911 AC system in one post. wow. good to know! LOL

Tell me about a shortcoming that needs to be addressed once the shortcoming of condensation and O-ring seal leakage is overcome?

He is the resident guru on so many topics I lost track! yet real science and data proves him wrong over and over on every topic.

Would you be ever so kind and point out some REAL science and/or data taht has been used, or will be used, to prove me wrong?

he lives in an area where they dont even use AC. stick to the swamp cooler WWEST!

It takes a serious lack of knowledge to point out that one should make use of a swamp cooler in an area of humid climates such as we have here in the PNW.

if you want cold AC on a 95 degree day with 85% humidity, ignore anything he tells you. Kuehl on the other hand will deliver what he promises.

As I have said before and bears repeating, every thing Kuehl sells will work and work well...but...

Needlessly so, mostly, and at GREAT expense.

Kuehl's product set, and air cooled 911 A/C system knowledge, is now more historic than otherwise.

Take a look at how the water cooled Porsches SOLVE this very same problem, in SPADES. Electric fans are used to provide both engine cooling AND A/C refrigerant condensing.

*** How can it be that those very same A/C refrigerant hoses were in use throughout the automotive A/C industry during the very selfsame period and yet only the Porsche 911 series suffered, consistently suffered, refrigerant leakage??

There are quite possibly 2 valid answers.

1.) Using ONLY the thermostatic switch to control the compressor clutch could have resulted in system overpressures beyond the O-ring sealed capability.

2.) An overpressure resulting from engien shutdown but with the condensor high side already at "maximum" pressure. No blower to pull cool air through the rear lid condensor and LOTS or convection heat from a still HOT engine now flowing upward through the rear lid condensor.

Oh, and let's not forget that many owners of these air-cooled 911's swap out the engine fan in order to get more cooling at low engine RPM. The condensor cooling fans might very well accomplish that need just as well.

[wwest]

Originally Posted by johann86911

Hello Porsche guru's.

Okay so I got the car back with running ac.

It's pretty poor with limited cooling and I'm thinking of asking the mechanic to upgrade the whole system.

My issue is that the engine dies when cold when the AC is on. It is also is a bit difficult to start when cold. is this a sign of issues with the cis or does the idle just need to be turned up? or some other alternative?

help please?

Not sure what the OZ stands for but if you really are in Melbourne ("melbun" as I was taught by a local) we may have a chance to meet soon. My company is currently in the midst of quoting a new upgrade to the Melbourne Railway computer control system to replace the one we did back in 2003.

[johann86911]

I have read a couple of posts saying don't talk about air conditioning or oil on this forum but wow!

So, further developments - I've discovered a couple of things which will hopefully assist all (including me)!

1. The car only stalls when I put the fan on the dash board and the fan associated with the AC on. If I only put the fan associated with the AC on, the car is fine.

2. when the car starts to move after being stationary, there is what sounds like a low grinding noise.

So - I'm thinking compressor? AC blower motor? electrical gremlin? all three?

On the whole - the system is operational if not super efficient, except for the above two issues.

Thoughts/ suggestions would be most appreciated.

Kuehl - funds wont extend far enough to a complete system just yet (although I must admit I am tempted).

WWEST - I'm actually about 40 mins out of Melbourne but happy to meet for a chat/coffee.

[kuehl]

Originally Posted by johann86911

I have read a couple of posts saying don't talk about air conditioning or oil on this forum but wow!

1. The car only stalls when I put the fan on the dash board and the fan associated with the AC on. If I only put the fan associated with the AC on, the car is fine.

A) Unplug the wire leading to the compressor clutch, the plug is adjacent to the oil filter. Check to see if the issue occurs with the compressor unplugged.
B) If you want a/c the a/c system and only a/c air you do not need to move the slides in the dash. However, if the issue is happens with the a/c off and the fresh air motor on (top slide in the dash) the possibly its the circuit overloading on the fresh air motor. The fresh air motor consumes about 5 amps nominal.

Originally Posted by johann86911

2. when the car starts to move after being stationary, there is what sounds like a low grinding noise.

Where is the grinding noise specifically coming from? Are talking wheel bearing, brakes, tranny, brakes....?

[kuehl]

Originally Posted by wwest

As I have said before and bears repeating, every thing Kuehl sells will work and work well.

Thank you.

Needlessly so, mostly, and at GREAT expense.

.
Its all in the eyes of the beholder. We all know you can't afford some things .

Kuehl's product set, and air cooled 911 A/C system knowledge, is now more historic than otherwise.

Yes. Statistics and history do help.

Take a look at how the water cooled Porsches SOLVE this very same problem, in SPADES. Electric fans are used to provide both engine cooling AND A/C refrigerant condensing.

Cars with radiators typically have the condenser in the front and a fan in the front or rear of that assembly. Porsche did not solve anything, they logically copied what works for water cooled cars. But this forum is not about water cooled cars.

*** How can it be that those very same A/C refrigerant hoses were in use throughout the automotive A/C industry during the very selfsame period and yet only the Porsche 911 series suffered, consistently suffered, refrigerant leakage??

Because the water cooled cars had about 10 feet of rubber hose whereas the 911 and 930 air cooled cars have 4 times as much.

1.) Using ONLY the thermostatic switch to control the compressor clutch could have resulted in system overpressures beyond the O-ring sealed capability.

Please provide your data on the system pressure exceeding the capability of the o-ring vs. flare systems.

2.) An overpressure resulting from engien shutdown but with the condensor high side already at "maximum" pressure. No blower to pull cool air through the rear lid condensor and LOTS or convection heat from a still HOT engine now flowing upward through the rear lid condensor.

The average high side pressure when the system is running ranges from 180 to 350. When the system is off for an extended period of time the average pressure at rest is 100. When a "normally" operating system turns off the system pressure drops because it wants to equalize (its simply a matter of the design). When you turn off the compressor the system pressure drops to 'at rest' pressure within 15 -30 minutes. Hence the system pressure in a "normally" operating system does not rise and and create leaks; actually there are fewer leaks when it is off. The more you use it the more you loose it.

Oh, and let's not forget that many owners of these air-cooled 911's swap out the engine fan in order to get more cooling at low engine RPM. The condensor cooling fans might very well accomplish that need just as well.

Hmmmm, so you say there are literally 10,000 or more 911 owners out there without a factory engine cooling fan? I doubt it, although there are quite a few endurance racer's with modified crank pulley to fan pulley ratio's; slower fans that is.

[wwest]

Originally Posted by johann86911

I have read a couple of posts saying don't talk about air conditioning or oil on this forum but wow!

So, further developments - I've discovered a couple of things which will hopefully assist all (including me)!

1. The car only stalls when I put the fan on the dash board and the fan associated with the AC on. If I only put the fan associated with the AC on, the car is fine.

Your battery, alternator, and voltage regulator all together form a CLOSED circuit. With the battery distantly located electrically from the other circuit components even the smallist resistive element can result in degraded operation, especially so for the CDI ignition. PWM, Pulse Width Modulation, is the method used to regulate the level of current to the alternator rotor and thereby the battery charging voltage.

The more you ask of the charging system the higher the voltage pulsing level will be all the way back there in the engine compartment.

My first suggestion would be to remove the battery post connections, burnish and clean the posts and connectors. The same thing with the battery negative connection to chasis ground. The front/rear interconnect at the starter warrants the same treatment.

If none of that works then temporarily install a (new?) fully charged battery to check if the charge rate itself is having an effect. When you install that fully charged battery a good initial test might be to unplug the external regulator. The CDI seems to be highly subject to initermittent failures due to voltages above normal. While the average voltage might be well within spec those PWM pulses may not be.

2. when the car starts to move after being stationary, there is what sounds like a low grinding noise.

SOP. light coating of rust forms on the rotors overnight, moreso in damp climates.

So - I'm thinking compressor? AC blower motor? electrical gremlin? all three?

Battery/alternator/regulator........effects on CDI

On the whole - the system is operational if not super efficient, except for the above two issues.

Thoughts/ suggestions would be most appreciated.

Kuehl - funds wont extend far enough to a complete system just yet (although I must admit I am tempted).

WWEST - I'm actually about 40 mins out of Melbourne but happy to meet for a chat/coffee.

Funds....try the $200 (US) fix first.

[wwest]

Originally Posted by kuehl

Thank you.

.
Its all in the eyes of the beholder. We all know you can't afford some things .

Afford? Me? I think it should be our audience that is of concern

Yes. Statistics and history do help.

Yes, that always represents a problem with new break-through technology. Wonder what folks like you though of Edison's light bulb vs the old reliable gas lanterns, or in my case kerosene, coal oil, lamps.

Cars with radiators typically have the condenser in the front and a fan in the front or rear of that assembly. Porsche did not solve anything, they logically copied what works for water cooled cars.

But this forum is not about water cooled cars.

No, but a comparison is well warranted. How much HEAT must the 996/997front fans remove, extract, from the condensor/radiator stacks vs what that single fan, restricted to the operational aspects of the air cooled engine RPM, perform? Needs thinking about, doesn't it?

Because the water cooled cars had about 10 feet of rubber hose whereas the 911 and 930 air cooled cars have 4 times as much.

So, would that mean, logically, that if our cars lose/require refrigerant on the
average of 2 years then other marques should require at least a 10 year service period. How many of us have driven those other marques for over 20 years and never needed service?

Please provide your data on the system pressure exceeding the capability of the o-ring vs. flare systems.

Not required, you did that yourself below.



The average high side pressure when the system is running ranges from 180 to 350.

Yes, and if by pure happenstance you switch off the HOT engine on a HOT TX day with the system already at 350PSI and with the TXV fully closed due to the evaporator being already at 32F..?? What would you suppose now happens as the HEAT from that HOT engine rises upward through the rear lid condensor..??

When the system is off for an extended period of time the average pressure at rest is 100.

Many thanks for the confirmation.

When a "normally" operating system turns off the system pressure drops because it wants to equalize (its simply a matter of the design).

Yes, but as you just stated, "only after an extended period of time".

When you turn off the compressor the system pressure drops to 'at rest' pressure within 15 -30 minutes.

Yes, But..compressor and engine, HOT engine, and with the evaporator at 32F what might be your estimate as to how high that initial 350 PSI pressure might rise within the first 2-3 minutes..??

Hence Really..?? the system pressure in a "normally" operating system does not rise and and create leaks; actually there are fewer leaks when it is off.

Methinks man speaketh with forked tongue..

The more you use it the more you loose it.

Wow, finally, something we agree on.

Hmmmm, so you say there are literally 10,000 or more 911 owners out there without a factory engine cooling fan? I doubt it, although there are quite a few endurance racer's with modified crank pulley to fan pulley ratio's; slower fans that is.

"..without a factory engine cooling fan.."

Don't think I said that but if I did it was mistaken.

I have understood the Ops to mean they wished to have more cooling at low engine RPMs, more fan blades, pulley ratio to turn fan faster.

[kuehl]

Wonder what folks like you though of Edison's light bulb vs the old reliable gas lanterns, or in my case kerosene, coal oil, lamps.

Actually it was Dr. Weston (Newark, NJ) whom developed the light bulb and it was Edison whom had the saavy PR. Then again Edison spent years infatuated with the plant life of Ft. Meyers for a filament while Weston solved the problem.

996/997front fans remove, extract, from the condensor/radiator stacks vs what that single fan, restricted to the operational aspects of the air cooled engine RPM, perform? Needs thinking about, doesn't it?

No thinking about it. This forum is about air cooled cars with limited front end room for naturally forced air or fan assisted condensers. And, fans running after the engine is turned off on a 996/997 or other "marque" were not intended to reduce a/c system pressures.

So, would that mean, logically, that if our cars lose/require refrigerant on the
average of 2 years then other marques should require at least a 10 year service period. How many of us have driven those other marques for over 20 years and never needed service?

Marques? Is this a Hemmings publication?
The rate of loss is relative to the amount of surface area. 911's have more a/c surface area because of the larger volume of hose; hence barrier hose reduces the permeation rate.

Yes, and if by pure happenstance you switch off the HOT engine on a HOT TX day with the system already at 350PSI and with the TXV fully closed due to the evaporator being already at 32F..?? What would you suppose now happens as the HEAT from that HOT engine rises upward through the rear lid condensor..??

1) The low and high a/c side system pressures equalize to the static level, rather quickly. If you doubt that connect a service gauge set and watch. The high side will drop from 350 down to the relative static psi based on the ambient temperature (refer to a refrigerant chart) and the low side rises to the same.
2) Amazingly the engine's heat dissipated up through the condenser does not raise the system pressures.

If you feel strongly about your hypothesis you have been tossing in every a/c related thread here in the forums then maybe you can take the conjecture to a higher level (no pun) and present a video for us.

Yes, But..compressor and engine, HOT engine, and with the evaporator at 32F what might be your estimate as to how high that initial 350 PSI pressure might rise within the first 2-3 minutes..??

No. The pressure does not rise. We have been working on 911's a/c systems since 1984. We use 3 different designs of service gauges, 3 different manufacturer's. Some of analog and some are digital, one has recording. They gauges don't lie. The result is always the same: turn off the a/c and the high side drops and low side rises and typically with 15 minutes or so both pressures are at a static psi relative to the type of refrigerant and the outside ambient temperature; look at a refrigerant pressure chart.

Really..?? .....the system pressure in a "normally" operating system does not rise and and create leaks (when the system is off) ; actually there are fewer leaks when it is off.
Methinks man speaketh with forked tongue..

You can think and conjecture what ever you wish however facts are facts.
Once again. Make us video of your rising pressure concept.