Grant Vortex 36 external boiler

[steveo1967]

Help!
I have a Grant oil external boiler. i'm getting hot water and no heating. It seems that the boiler is calling for hot water constantly as the hot water pump runs all the time. So far I've replaced (with the help of an engineer who has now given up!!) the following on the advice of Grant, without success.
Heating and HW PCB's, Flow switch, Pressure switch (it started to leak which was the initial fault) and a relay (No 3 I think). Spent a fortune so far and still no change and now Grant Technical have run out of ideas.
Would love some input if anyone can help me please?? Thank you in advance of anything you can add.
Steve

 

[Boilerman2]

Disconnect the Flow switch and see what happens? it is possible on the 36 Combi model that the paddle of the flow switch is fouling the pipe in which it is inserted, if disconecting the flow switch restores the heating, then the answer is to carefully file away the paddle untill it just fits without fouling TBH there's not a lot else it can be!!

Grant Service Agent.

 

[steveo1967]

Thank you. Already done this and filed the switch down. It tests fine with and without flow. Any other thoughts? Thanks again. Steve

 

[Boilerman2]

I did go to one a while ago with incorrectly wired control panel I had to sit with the manual wiring diagram and go through each cable one at a time, one of the three relays was wired incorrectly - a very rare fault though, but you do seem to have covered all other bases!!