911 SC and 3,2L A/C and heater

[Nico911]

Hi again Pelicans.
Is it normal for SC and 3,2L models to have poor A/C and heating systems. I'm shopping around for an '80s 911 and I'm starting to believe that this is very usual on these models.

Only problem is that I live in Montreal and spring and autumn rides can be chilling, and summer are very hot and humid in here... So, I think twice...

... I thought I knew a lot about Porsches...

Any inputs welcome.

Nicolas

[rokemester]

I have an 87 Targa with an automatic heating controller which doesn't work. I can open and close the flapper boxes (similar to a VW). I get PLENTY of heat. No worries. AC is another thing. AC has been converted to R34 but it can't hold a charge. AC is minimal to non-existant. If you search on AC on this forum you will find that air cooled P cars aren't known for their cooling capability.

Happy to have the Targa top!!

[mlfox]

Suggest you do a search on this forum... hours of read, facts, and opinions on those subjects.

Regards,
mlfox

[DRACO A5OG]

Generally Speaking, NO they are not the best AC but heaters if plumbing is okay will be more than adequate.

For me, I am a bit lucky, I just had to replace dryer and driver side hose to rear condensor and AC works great during SoCal summers.

[Nico911]

Thanks guys. I appreciate.

[Scott R]

Search "Mr. Ice Project" for the AC, and search "Mystery Train + footwell blowers" for heat. I have more heat, and more AC than I need.

[wwest]

Originally Posted by Nico911

Hi again Pelicans.
Is it normal for SC and 3,2L models to have poor A/C and heating systems. I'm shopping around for an '80s 911 and I'm starting to believe that this is very usual on these models.

Only problem is that I live in Montreal and spring and autumn rides can be chilling, and summer are very hot and humid in here... So, I think twice...

... I thought I knew a lot about Porsches...

Any inputs welcome.

Nicolas

1980-1988 A/C upgrade ??

Having adequate cabin heat involves 2 aspects, one, the engine/exhaust already up to operating temperature, and two, heated air volume movement.

While there is an axillary, compromised(***), fan/blower in the engine compartment, the major contributor to heated air volume movement into the cabin is the engine fan/blower itself. So if you're idling along in stop and go traffic on a COLD day or night the best advice for the moment would be to keep the engine spun up as much as is possible.

In order to allow the engine fan forced air volume flow to bypass the axillary fan/blower the squirrel cage blower wheel is set back from the intake face about 1/2", resulting in really poor air movement efficiency.

The A/C...

The MAJOR shortcoming of the factory A/C , perhaps the ONLY shortcoming insofar as cooling capacity is concerned, is inadequate refrigerant condensing capability.

A second concern, expressed and experienced by many, is refrigerant leakage over time, even as little as one season.

I quite firmly believe there is a common answer for both.

Add 2 electric, 12 volt, thin radiator cooling fans to move airflow downward through the rear deck lid condenser. Add a trinary switch on the high pressure side of the system. One switch section to supply 12 volts to the fans whenever the high pressure side is elevated, even if the engine has just been switched off. The other section (two switches in series internally) to control the compressor clutch.

Some, many, actually, will advise you to switch out the entire "non-barrier" hose set to more modern versions. I am NOT of that school, thought.

Those same hoses (and o-ring seals) where used industry-wide for/in this same era with NO complaints of the type EXCEPT our air-cooled Porsche's.

So, what is different..?

There are 2 candidates.

1.) Engine HEAT: High side refrigerant pressure rising above the hose/o-ring design standard as a result of engine HEAT, CONVECTION & RADIANT engine HEAT, rising through the rear deck lid condenser POST engine shutdown.

2.) Poor compressor clutch control design: With the factory control and the A/C enabled the compressor clutch will remain engaged until the evaporator core reaches the thermostatic setpoint. So without an over-riding control the compressor might continue to run long after the high side pressure reaches the design limit.

Here in my area the major problem for me occurred years ago driving my '78 over the snow covered pass at night in winter. Keeping the windshield defogged involved keeping the engine revved enough to ROAST us with the mass of HOT air reflected from the windshield. Also had the windows rolled down slightly to allow more "fresh" sourced cabin arflow.

NEVER did that again.

Speaking of which, later 911 models, our '88 Carrera, have 2 auxillary blowers to assist defogging of the windshield.

[wwest]

Like these:

[Jay H]

In regards to heat, I drive my '84 3.2 Carrera in some cooler weather during the fall and spring where I'll see mid '30's for temps and I used to use an '86 911 for all year round and drove that in single digit temps here in Wisconsin. I can melt my feet with my '84 and I think my '86 threw enough heat to double as a blast furnace. Even in single digit temps. So, heat is very effective in the later air cooled cars IF all the systems are working as how they did when the car left the factory.

The key to the heating system on these cars is insuring the engine mounted ventilation system fan is operating, the heater boxes are intact and work correctly (meaning, they close fully), the flexible hoses between the heat exchangers and body enclosed heat ducting are not rotted away, the air directional level controls work in the dash (meaning the heat lever routes air between foot wells and windscreen and the fresh air vent closes fully to keep cold air out) and the auxiliary fans in the front wheel wells are operating.

Many times, these systems are not fully understood and we may not even know these fans exist, if they work, the ducting is rotted away or not operating correctly or the levers won't adjust the dampers correctly. Get everything back to factory specs and the heat will be more than enough even in very cold climates.

[SilberUrS6]

Originally Posted by wwest

Like these:

lol, just lol.

[wwest]

Originally Posted by Jay H

In regards to heat, I drive my '84 3.2 Carrera in some cooler weather during the fall and spring where I'll see mid '30's for temps and

I used to use an '86 911 for all year round and drove that in single digit temps here in Wisconsin. I can melt my feet with my '84 and I think my '86 threw enough heat to double as a blast furnace.

Yes, while crusing along at highway speeds if you need more heat you can simply downshift temporarily to increase the cabin airflow. Idling along in slow or stop and go traffic is an entirely different matter.


Even in single digit temps. So, heat is very effective in the later air cooled cars IF all the systems are working as how they did when the car left the factory.

The key to the heating system on these cars is insuring the engine mounted ventilation system fan is operating, the heater boxes are intact and work correctly (meaning, they close fully), the flexible hoses between the heat exchangers and body enclosed heat ducting are not rotted away, the air directional level controls work in the dash (meaning the heat lever routes air between foot wells and windscreen and the fresh air vent closes fully to keep cold air out) and the auxiliary fans in the front wheel wells are operating.

Many times, these systems are not fully understood and we may not even know these fans exist, if they work, the ducting is rotted away or not operating correctly or the levers won't adjust the dampers correctly. Get everything back to factory specs and the heat will be more than enough even in very cold climates.

"..The key to the heating system on these cars...." is keeping the engine revs high enough that the engine fan moves enough VOLUME of heated airflow into the cabin. The engine mounted ventilation fan will suffice only in coolish temperatures, NOT COLD temps.

[Jay H]

Originally Posted by wwest;

Idling along in slow or stop and go traffic is an entirely different matter..

However, the auxiliary fans in the footwells were added (during the SC years?) just for such situations where you had to idle and needed heat. Those fans in the footwells (controlled by either the "automatic heat" or manual heat setup between the seats) will help bring heat forward when engine speeds are low.

I fully agree with wwest that on the early cars without auxillary cabin blowers, you need to be at freeway speeds to get any significant heat to come forward. I have to assume that Porsche recognized this issue on the early 911's and then introduced the foot well blowers and various stages and switching of these blowers.

I have manual heat on my '84 (and had it on the '86 as well), all my blowers work well and I've got new heater boxes and hoses. With both levers in the full up position, the aux fans in the footwells will turn on. Then, with the three position knob between the seats on "3", I can melt my shoes at idle. Yes, even at 0 degrees F. I can not run on the freeway for very long with all these fans running and blowing heat. It's just too hot.

My brother has two SC's with broken engine compartment blowers and inoperating footwell blowers (in both cars) and the heat output is pathetic, even in moderately cool temps. His '70 911 has adequate heat only with the motor spinning at a decent clip. His '66 911 is similar. With these cars ('66, '70, two '83's, an '84 and '86) in the family, you can see first hand how Porsche upgraded the heating system as things progressed.

These goofy heating systems do work well on the SC and 3.2 liter cars when all is working and hooked up correctly.

[911dean]

The heat in my '84 is too hot. My ac blows cold air at you but is inadequate to cool the cabin. I'm leaning towards just removing it.

Dean

[wwest]

The level of heated airflow can be modulated, moderated, using the left and right levers that adjust the continuously variable cabin airflow/dump valves under the car near each rear wheel. But it remains true that what airflow you adjust the system to will likely be HOT.

I'd have to go and actually try it but it seems to me that there is a control setting wherein FRESH and HOT airflow to the footwell can be MIXED in order to moderate the HEAT level of the system outflow air volume.

The way I do it if no passenger is on board is close my side off and heat the cabin using only the passenger side airflow.

The factory A/C is most defintely sub-standard but if you would like to have decent A/C rather than none:

1980-1988 A/C upgrade ??

[brads911sc]

Lol

Originally Posted by wwest

like these:

[kuehl]

Nicolas,

Heat:
As far as heat, if your heater system is in good shape you should not have any major complaints, however the defrost vent system on the windshield is not the greatest is dispersing of air but you could modify it. As far how hot? , lol, with these cars you get heat instantly.

I have an 87 cabriolet (no insulation above your head). I removed the engine aux heater blower and I'm just running foot well blowers. At 18 F outside in the winter I have more heat than I need. So I'd review Scott's comment about what Mystery Train and others have done.

A/C:
2 issues with AC; integrity (leaks) and performance. There are tons of threads here on what works and what does not work (blower fans under the deck lid condenser are simply not going to cut it for you).
A good reading primer for your on AC is
The Mr. Ice Project

[wwest]

Originally Posted by kuehl

Nicolas,

Heat:
As far as heat, if your heater system is in good shape you should not have any major complaints, however the defrost vent system on the windshield is not the greatest is dispersing of air but you could modify it. As far how hot? , lol, with these cars you get heat instantly.

I have an 87 cabriolet (no insulation above your head). I removed the engine aux heater blower and I'm just running foot well blowers. At 18 F outside in the winter I have more heat than I need. So I'd review Scott's comment about what Mystery Train and others have done.

A/C:
2 issues with AC; integrity (leaks) and performance. There are tons of threads here on what works and what does not work

(blower fans under the deck lid condenser are simply not going to cut it for you).

Kuehl, as he should be most willing to admit himself, lacks any real, well grounded, foundation whatsoever for making this statement. No actual experience, no trials, and apparently very little knowledge regarding this aspect of improving the factory A/C operation.

A good reading primer for your on AC is
The Mr. Ice Project

On the other hand Kuehl will be more than willing to take your money, oodles and oodles thereof, for his well proven, known to work, solution.

That's the one and only reason the rear deck fans will not work in Kuehl's opinion, no money for HIS pockets.

If you're going to go ahead and buy from Kuehl, buy an add-on condensing system FIRST, that will more likely than otherwise bring the factory system operation up to acceptable standards even in Austin TX.

But even so it might be a wise move to also add the trinary pressure switch, <$50.00, both to protect the compressor from self-destruction with low refrigerant in the system and to prevent the compressor from over-pressuring the system. Assuming the add-on condensor system you choose has an integral fan, as it most certainly SHOULD, you could wire the third pressure switch such that it will run the new condensor fan as long as high refrigerant pressure persists, even with the engine switched off.

This latter effort might well prevent the system pressures from rising so high that leakage results.

[wwest]

Speaking of the Mr. Ice Project I'm guessing that it was composed, written, long before modern day electric cooling fans became widely available and therefore relatively inexpensive in the marketplace.

Time for a revision??

I personally suspect that it was the widespread conversion of passenger vehicles to FWD and then F/awd (when would YOU say that happened?) that resulted in the development of these highly efficient and relatively inexpensive radiator cooling fans.

Strange: When I turn on the A/C in my Lexus RX300 ( or most likely with any modern day A/C equipped vehicle) the radiator/condenser fans come on in low speed immediately, then at high speed when the compressor clutch is engaged or if the engine coolant temperature approaches the upper limit

Also, if the engine coolant begins to rise too high the A/C compressor clutch circuit gets disabled until the coolant temperature declines down to the normal operating range.

So, if this works, fans used to cool the refrigerant within the condenser EVERYWHERE else in the automotive marketplace, why do so many take the position that it will not, cannot, be used in the same way in our air-cooled Porsches..??

Kuehl..?

[Scott R]

Does your Lexus have an engine cooling fan? And is the engine in the rear under a curtain of negative air pressure? Likely not.

[kuehl]