Changing ST699B programmer to ST6400C

[repairman26]

I have tried changing these programmers over using the supplied reference chart enclosed in the box, All the wires matched and connected but on test the ST6400C made a noise like a relay chattering when the heating switch was selected but not when selecting the HW position, The boiler did not fire up when either calling for HW or heating.
Checked all connections in junction box which is a Y plan circuit, Boiler is a Hideaway 40B, I have put the original ST699 back and all OK again the wall stat is an old mechanical one and not sure which Honeywell model it is ....Anyone help please!

 

[bster]

was the st699 wired up for 240v switching (Terminals L-5-8 linked)?

 

[repairman26]

Yes! wired exactly like that but no mention in the new one about the links.

 

[bster]

the new one doesnt need them as it takes the 240v internally from the LEN connections.
I though i'd ask just in case the ST699 was not wired for 240 this would have meant that you were sending 240 to things that didnt want 240 - get me

and if you have defo connected the wires correctly on the new one should be HW off, HW on and CH on and LEN. (no CH off)

 

[repairman26]

OK thanks for your help, perhaps a faulty programmer then ?

 

[bster]

might be but i'm no expert!, wait for someone with a bit more electrical savvy to give you a post before you take it back