I think it is a great feature and a nice retro touch... but I am wondering: if you have access to electricity then there`s a chance that the car is already parked in your garage and needs the heater less than if it was parked outside!
I imagine it is a great idea for cars that are mostly parked in driveways for overnight.
They work by the way. If it keeps the coolant just -let`s say- 20degrees warmer, then it is already a substantial difference for your engine (less wear at start-ups).
I have one installed in my spare d24t and this Winter I will do an experiment on how many degrees it can increase the coolant temps in certain temp ranges.
Hopefully I`ll have the time. I think last time I plugged it in it needed about 20minutes to show substantial increases in coolant temperatures. Also, I was using digital thermometer on the surrounding areas and they showed a good amount of increase in temps relatively quickly.
I believe they really are able serve the purpose they were designed for.
Canada drivers will send their replies here, I am guessing. And maybe some Upstate NY diesel owners. These heaters also came factory on certain vw models in Europe, I remember seeing them as late as the late 90`s or so.
The O-ring can be a risk factor if the unit is "very old", even if you found a `new` NOS one that has never been installed on a vehicle. Probably easy to size it and replace with modern rubber.