Quick duo valve query

[chris846]

Star shows a duo valve stored fault. No idea what the duo valve (valves?) was/were so I checked this forum and now I'm an expert ready to roll, ahem.
Can anyone confirm that the valve operates by pulsing fully open/shut, rather than opening progressively?
Also, with ignition on, but engine not running and everything pretty cold - does the duo valve click away hopelessly if the heater controls are set hotter than the lukewarm coolant can provide?
Thanks all
chris

 

[balge]

hi
the duovalves on both my W124's buzz like one-oh with the the switch on, (engine off) and get quite hot too!
I think that's normal....
Pretty sure they open and close quickly to control the flow for different heater settings, rather than hold a fixed position, as you say

cheers
balge

 

[BlackC55]

Do you have a problem with the heater system?

Stored Duo vave faults always come up and generally can be ignored. We call them sporadic faults. BS fault codes.

 

[chris846]

No - no problem that I've noticed and yes, it was only a stored fault. Just had no idea what a duo valve was/did!
I also always get a headlight level stored fault (factory xenons), although there never seems to be a problem with them either.
cheers
chris