The Electro-Magnetic Valve (Ferrari part # 61079000) refers to an electrically-driven valve that controls the flow of coolant into the heater core to regulate the generation of cabin heat through the HVAC controls accessible by the driver.
This part is used in the following Ferrari models: 456GT, 512TR, F40, F50, F512M, Mondial 3.2, Mondial QV, Mondial T, Testarossa 1997 and 1990.
The problem: overtime the valve starts working intermittently, thus causing the generation of heat to be erratic. Once the valve stops operation altogether no heat will be generated into the cabin regardless of the temperature control position.
The solution: once the valve starts malfunctioning the most common solution is to replace it. Unfortunately this part is no longer available through Ferrari and sourcing a replacement is both time-consuming and quite expensive.
The Affordable Supercar solution: Discussing this issue with a variety of technicians in our contact network we have learned that in most cases this valve can be restored to full functionality by replacing the inner plunger (not available through Ferrari). This requires that the valve be opened, and the internals replaced with a suitable set of parts. First we obtained the replacement inner plunger, then we had the customer remove the valve (we provided ample guidance on how to do it) and ship it to us. We fixed the valve and shipped it back to the customer who proceeded to install it. Everyone likes a happy ending, and we are pleased to report that months later the customer contacted us to inform us that the refurbished valve is still working.