Solved 1978 911SC Overheating & AC Issues in 36°C (97°F) Heat - My Custom Cooling System

[911SC_Japan]

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!

[911SC_Japan]

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!

[piejesu]

I also live in Japan and am suffering from this terrible summer heat. I installed an electric air cooler system (non Classic-Retrofit) in my vintage Alfa Romeo, but it hasn't been as effective as I had hoped, so I am looking for ways to improve it.

After reading your post, I was truly amazed at the high level of cooling performance you’ve achieved with the electric cooling system. If there are any tricks to it, I would greatly appreciate your advice.

For example, “dual-condensers are mandatory for this result” or “the Classic-Retrofit’s Compressor offers vastly superior performance compared to those from other manufacturers, so you have to replace the compressor at first”, etc.

[911SC_Japan]

Hi piejesu,

Thanks for the tips! 

Before replacing the compressor, I suggest checking the refrigerant temperature at the condenser outlet. Ideally, it should be around 50°C (122°F); it loses efficiency above 60°C (140°F).

I recommend using a wireless data logger to monitor this during drives. This Bluetooth sensor lets you track data on your phone: 

https://amzn.asia/d/0bc6s7EQ

Good luck with your setup!

[piejesu]

Thank you for your advice! I will get the data logger and check the temperature as you advised me.

Regards,