The monovalve case is just a case and isn't prone to leaking. The solenoid can be replaced as a cartridge but there's no need to do so unless you have heat at standstill that fades with speed. Come to think of it, I don't know if replacement cartridges are still available.

I don't know what safety is gained by replacing a functional OE aux pump. Put a fuse on it like you're doing with the monovalve and don't think about it until the fuse blows. Try this - show a friend the aux pump electrical connector. Have the friend choose to unplug it or leave it connected without telling you the choice. Repeat for a few days. At the end of the experiment compare notes as to which days the aux pump was offline and which days you sensed it was offline. It's not conclusive. I suppose if you couldn't tell the difference it could mean the aux pump isn't healthy

If you need to invest time and money in the heating system, invest it in replacing the vacuum pods throughout the ACC ducting and a can or two of evaporator core cleaner.

Sixto
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