I have this this same problem (leaks = from rear heater). I bought a new core for $100 (not original) and found the = switch (or valve) under the seat might leak also. But I didn't change it = that time. Few weeks later it still leaks. I explore the switch = to the parts and found the sealing (or rather hole rubber plate) of the shaft = has worn out. What should I do?..buy a new part (expensive)..put a common = pipe valve (made of brass) instead (mucho work)..

I decided to make a same = size/thickness blind rubber plate => now the switch is always on..but it is also really = cold here in Finland and you can adjust amount of heat by adjusting the speed of = the fan.