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Here is a snapshot of my engine bay. As you can see, it looks completely stock! The beauty of this system is that it's a 100% "stealth" upgrade. There are no visible fans, no altered aesthetics, and absolutely zero modification to the chassis—just pure modern performance hidden inside. You'd never guess it could beat 36°C (97°F) heat just by looking at it!

Hi everyone, I wanted to share a breakthrough with my 1978 911SC. In Japan's brutal summer (36°C / 97°F), the factory AC was useless and oil temps were always on the verge of overheating. To solve this, I developed a custom, completely bolt-on cooling system that requires absolutely zero modification to the original chassis. It fits beautifully in the limited space. A key feature is the "After-Cooling" capability—the system automatically boots up to cool the engine down even after the ignition is turned off. A big shoutout to Classic Retrofit (CRF); I am using their high-output alternator to perfectly support the power needs of this entire system. On July 31st, I finished a 350km (217 miles) long-distance test drive in high ambient temperatures. According to my data logger analysis, the oil temperature dropped drastically and stayed in the safe zone throughout the trip. Test Run Data (July 26th): To test the system in a real-world scenario, I took a 1-hour round-trip drive on July 26th to pick up Burger King in the blazing heat. Image 1 & 2 (Dashboard Gauges): This is a photo of my dashboard during the drive. The oil temperature gauge stays perfectly in the safe zone, and the factory cabin vents are finally blowing ice-cold air. Image 3 & 4 (Data Logger): This graph shows the raw data from my test drive. THSensor 1 tracks the AC condenser temperature, and THSensor 2 monitors the engine oil temperature. As you can see, the cooling system actively managed both temperatures, keeping the oil incredibly stable. I’m currently tweaking the system for maximum efficiency. Just wanted to share that keeping our air-cooled cars running cool even in extreme heat is truly possible!

I am having the same issue. No voltage on white wire to fan relay/battery isolator relay. Compressor wouldn't run until I deleted the battery isolator relay. Now it runs until it draws too much current and shuts itself down. Watching the diag screen on Putty I can see that the compressor current is reaching the setpoint for fans to come on and the system switches from "Fan=0"to "Fan=1" but no voltage is sent down the white wire. Even if I command the fan on there is no voltage on the white wire. I've backprobed the pin for this wire at the grey ecu connector and there is no voltage. When I apply 12v to the white wire's terminal on the relay (term.86) the fans come on. The red wire that feeds the white wire has battery voltage and the relay functions normally when tested. I've tried multiple relays just to be sure. All fuses, grounds, and wires are in good condition but the ecu has never sent voltage to the white wire. Thanks, Adam Mills Heckmann & Thiemann Motors

The third area to consider is the electronics, wiring and the control switches. SWB 911's have a variance in the factory blower controls - with many having no fan switch, so you will need to install new switches and connect them to our A/C system. Our 'Gen2 Blower's are supplied to plug straight into the original factory F and G body loom to use the factory slide controller on the dash which comes with a three speed fan configuration. For the SWB installation you will have to replicate this using the plug and the pins are available, as per the example pictured below: 4 pin connector housing for fuel level sender. Porsche 911 / 928 - 90161289101/2 | Design911 The wiring details are key. These are fans are ground switching. Please take care to follow the original F / G body Wiring pin out. NB We use our own colour designations, Black, Orange Red Yellow. Black 12v, (Fused) Orange 0v (Fast) Red 0v (Medium) Yellow 0v (Slow) This can be wired up any number of ways, including any of these: 3 speed, rotary, toggle switch, push buttons. We suggest this is all done using automotive gauge wiring rated for 25A and fused at 15A. Mounting and positioning of the switch is down to the installer as there's a number of locations this could be fitted it is down to personal preference.

The second step for SWB vehicles is to address the ducting. SWBs have notably fewer paths for air to enter the cabin (than later cars). This is a challenge if you prefer to not cut the body metalwork. HOWEVER there are some clever workarounds. The first and simplest option is to feed into the original heating system ducting. Simply connect an outlet of the blower to this. You may need to plug openings and gaps where the original scoop interfaced. Another option is to use our Round Vent for 911 Clock Position Some years featured a clock, others did not. We appreciate that this is a compromise (to lose your clock) but our recommendation is to be cool and check your watch! The picture below shows a car with blanking panel in the clock position. This picture, below, uses dual clock vents which works well in extreme climates. You do also have the option of forming new openings in the car body to add under dash vents. We do not warrant this and this is entirely at the risk of the owner. Pictured below is an install that used our Round Vent for 911 Clock Position placed in new openings (cut into the body), to act both as footwell vents and to allow for recirculation into the blower to aid system performance.

The first component to address is the blower / evaporator unit. Our 'Gen2 Blower' is a direct fit for F and G Body cars. It is not a direct fit for SWB variants. The factory fibreglass 'scoop' / air inlet needs to be remodelled to integrate with our blower unit. We recommend removing the black plastic air scoop that comes attached to our blower, and then offering the blower unit up into position before making any modifications. NB The image above shows the blower end caps and frame, as a 'skeleton' for visual clarity. Once the angle of the blower unit is established you can make modifications to the factory fibreglass scoop. Please measure carefully before you cut any materials. We recommend the addition of a new lower support for the blower. See picture below: Once the scoop is attached it should look something like the picture below: The picture below show the fibreglass scoop attached the blower and installed into the vehicle.

Our A/C system is designed for installation into Porsche 911 models years - 73 through 89 however it is possible to fit them into the earlier SWB models from model years '65 to '69. Modification will be required to both the car and to the supplied kit to enable it work effectively in 911 SWB vehicles from this period. To be clear the current A/C system is not 'plug and play', and will require some modifications to make it work and fit effectively. We are working on a SWB specific A/C system but at present there is no date or price confirmed. Please see the steps required below to make this system work in a 911 SWB.

The 993 alternator should be fitted as per standard Porsche service manual. Key notes to be taken however are: The larger spacer (red arrow) is the first spacer to be fitted, because our alternator has an inset bearing, this brings the mounting face level with the OEM Alternator. The spacers arrowed green can then be used to match the height of the original spacer from the original alternator pulley assembly. The combination of 3 spacers should cover all models, e.g. single pulley (RS) / double pulley. Use as appropriate. Other than this please follow the Porsche Service manual for all fitting and technical information Regarding the rear 'cone', this should be fitted as it is also a load spreading device for the alternator nuts.

I guess this is subjective to some degree. Personally, I have never experienced this because the engine is usually producing more NVH than the compressor! Have a great trip!

This isn't an AC settings issue, it is definitely alternator / charging system. These alternators produce 75/80 amps at idle. Either the 'exciter' isn't working ( which is in the clock instrument) or there is wiring issue or perhaps a voltage regulator issue.

at 2500-3000RPM it produces around 60A max when measured at the alternator

Coming back to this we never got the charging issues resolved. Even with the 240A alternator and serpentine belt it still only produces 20A at idle of 800rpm. At idle the AC system drains the battery dropping battery voltage to as low as 11.8v. I've tried all sorts of settings in the AC system but when the compressor is on it just drains more than the alternator is capable of producing. I see everyone saying this alternator can produce 100a at idle but I'm just not seeing how.

Any update as to when the new heat pump and control system for the 911 might be available???

Jonny, hi! Yes, the original foam dampers were used at first, they were mounted according to the instructions. With the new mod the vibrations disappeared almost entirely and I no longer notice them inside the cabin. I'm quite pleased with the result, after about 100km of testing. Next month we're going on a 5000 km trip around the South of Europe and the AC will likely be used a lot. If there are still issues I'll write here. The 911 has the old F-body, from 1970. Perhaps the chassis that we have has a slightly diff resonant frequency or there is some other contributing factor that couldn't be anticipated in the original mounting design.

Did you use the foam rubber strips under the top bracket supplied?

Used four rubber dampers for an improvised compressor suspension. Tests next week 🙂 I

Hello, When the compressor is on a vibration is heard / felt. What advice do you have to remove or dampen these vibrations? We're thinking of inserting rubber between the mounting bracket and the chassis. Good idea?

Install the ECU: 15. In the fuse box, remove the left side screw that goes into the bulkhead - this will release the metal bar that holds the fuses. 16. On the left side, if there is a relay behind this bar, relocate it to the right side of the fuse area. 17. Slide the ECU behind the bar and connect the black and grey connectors. 18. Replace the left side screw and use it as a ground point for the black wire with ring terminal. 19. Connect the red wire to the fuse, as pointed out on the fuse panel cover. You will need to splice in a short length (75mm - 100mm) of 2mm wire to connect this. 20. Note that during commissioning, you will need to refer to the small screen in the ECU - it displays important information, we recommend that you leave the ECU loose until the system is setup. 21. ECU shown in situ for reference.

Refit the orginal black dash tray. This does need some modification to let the two vent pipes through. Do not reassemble the rest of the dashboard until the system has been tested.

Installation pictures coming soon. Please refer to RHD install as the LHD is almost a mirror image of the RHD. We are looking to produce a set of photos for this section. If you have a LHD Landrover install, please do contact us sales@classicretrofit.com

Hi Peter, that is good to know and apologies your post slipped through the net.

Identify the 2 halves of the replacement plasic 'lid'. Attach the cut foam pieces to each lid (foam sticks to the underside of lid - e.g. inside the triangular section) and install in the car using the screws you previously removed from the original metal lid. Fit the 2 windscreen vent air-valves (with servos attached) on top of the replacement lids. Fit the 45mm duct connectors on top of the air-valves; the windscreen vent restrictor gets sandwiched between the top of the passenger side air-valve and the 45mm duct connector. On the passenger side place the air restrictor element in between the actuator and the air hose. This balances the air flow between the drivers and passenger side Attach the 2 windscreen vent valves to the air hoses that go to the windscreen vents. You can use the original windscreen screen demist hoses but you may need to shorten them slightly.

If possible, have the system pressure tested with nitrogen at 150- 250 PSI. This will immediately show any leaks due to bad hose crimps or torn o-rings. Fill the system with 600g of R134A refrigerant. Do this with the system OFF. Do not fill with 'cans' - use a proper A/C filling machine or take the car to an A/C centre. Do not add any oil. Oil is already in the compressor.

11. On the cabin side, turn the harness to the centre of the car. 12. Feed the 12 way grey and black connectors, the ground lug and red power input through the hole in the rear /centre of the dash, down to the fuse box (remove the fuse box cover first). 13. Connect the grey 20-way connector and black 12-way (fan) connector to the back of the control panel. 14. Connect the two windscreen servo connectors - NB it doesn't matter which is which. 15. Connect the 12v interior lights wire - confirm this is the correct wire by turning the side lights on and test with a meter.