heating only with water on

[ozzy]

hi I can only get the heating to come on with the hot water. Water ok on it's own. heating use to ok on it's own but not now. any ideas please

 

[GasmanxxxR1]

looking at your other post your 3 port probably is at fault here or something is going on with the grey wire

 

[Halesowen1]

Possibly Programmer.

 

[stevetheplumber]

depends on the system if its gravity hot water thats the norm

 

[PRplumb82]

Sounds like 3port valve is faulty to me