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After more than a year of development, I finally completed the Solid-State Cooling Fan Relay for the late model 944 and 968! This relay is specifically designed for dual cooling fan equipped vehicles. I am still working on one for single fan vehicles. I made two versions of it, “Standard” and “Diagnostics.” The standard version is a direct replacement for the factory mechanical relay. The diagnostics version has buttons and LEDs to quickly verify and diagnose cooling fan functionality.
Here are pictures of the two Solid-State Cooling Fan Relays side by side:
Below are internal pictures of the new F9T Solid-State Cooling Fan Relay next to various original mechanical cooling fan relays. As you can see, the “Cooling Fan Relay” actually has several “internal relays.” Each fan has a dedicated relay for low-speed and high-speed operation. However, the earlier versions have a fifth internal “control” relay that was later replaced with numerous electronic components. The factory went through several updates to the dual fan relay with the latest version being “04.” Obviously, the F9T relay takes a more modern approach. The mechanical relays are replaced with four independent “smart” power switches. These power switches are designed to drive inductive loads such as automotive cooling fans or smaller starter motors.
And it is The diagnostic version I tested was very helpful in diagnosing a malfunctioning radiator thermal switch in my S2. With the engine off you can use the Fan Test switches to run the cooling fans on Low or High speed to verify they are working and there aren't any problems with the fans or fan resistors, etc. Then with the engine running the Green and Amber lights will tell you what speed they are running based on input from the radiator thermal switch. In my S2 this confirmed the fans jumped directly to Fast (amber light), indicating an issue with the thermal switch.
Checking the Delaware Porsche parts site there's yet another relay revision to "05"
We're very lucky to have this company serving the Porsche community. I wonder Joe knows there's many, many opportunities for his talents across many other makes of vehicles. Especially in light of the decline in quality of replacement parts in the aftermarket. I bet the Ford crowd would to see solid state fuel pump and 'EEC' relays...Or better yet, a genuinely high quality, reliable TFI module!
The website shows they are ON SALE now: $150 for the diagnostic version and $120 for the normal version. This is a bargain as the current "05" version from Porsche is more than $180.
Last edited by Tom Pultz; 08-08-2021 at 02:39 PM.
Reason: Add link & info
The website shows they are ON SALE now.: $150 for the diagnostic version and $120 for the normal version. This is a bargain as the current "05" version is more than $180 from Porsche.
08-06-2021, 12:13 PM
Solid-State Cooling Fan Relay
The diagnostic version I tested was very helpful in diagnosing a malfunctioning radiator thermal switch in my S2. With the engine off you can use the Fan Test switches to run the cooling fans on Low or High speed to verify they are working and there aren't any problems with the fans or fan resistors, etc. Then with the engine running the Green and Amber lights will tell you what speed they are running based on input from the radiator thermal switch. In my S2 this confirmed the fans jumped directly to Fast (amber light), indicating an issue with the thermal switch. 
