Help needed Pulsacoil 2000

Hi
I have a pulsacoil 2000 with a greenbrook t72 timer which appears to have been left unused/unserviced for a period of time. When I first encountered the system I noticed the header tank was empty so I did not power up the system. On further examination with help from this forum I found both heaters has leaks from the rod thermostats. I drained the system and fitted two new xb080's heaters with rod thermostats. I refilled the system, bled the pump and connected the bottom heater to the standard tariff 'boost' to prove the heater via the terminal strip 5,6 & 7. The heater did not work. I confirmed electrical supply to the terminal strip, psc, relay & the heater on the 'live' side but could not confirm a 'circuit' on the neutral side. Am I missing something? Or do I need to replace the power relay? I have read a lot about issues with dhw and phe sensors but I did'nt think they would prevent the heaters working.
Incidentally, the pump does not appear to operate on opening hot water taps but it does spin freely and there is no separate overheat thermostat fitted.
The psc gives the normal led flash sequence, the green light appears broken and the red light is off.
Can anybody help please?

Well you need to put the timer on.
And with test leads check the heater / rod stat has a supply.
If the unit has been standing empty for a long time things can stick / jam etc.
Bottom of the pump between the pump and valve is a brass housing inside that is a single check valve.
Could be stuck but doubt it.
Tried putting a supply onto the pump? See if it runs that way?
Did you try the ON peak heater & the OFF peak?
Unit needs a supply to run / work as in the PCB / pump etc.
Also again I doubt it but it has been known for the pump impeller to break off inside the pump.
So although free and spinning it would not work.
You need to check / recheck your supply. The ON peak & OFF peak as well.
Timer could be dodgy too.
Mike

Thanks Mike, I had power to the system and set the timer to standard tariff boost and temporarily wired the bottom heater to that circuit. I used a simple mains tester screw driver and confirmed 'live' on the psc, pump, one side of the power relay and the heater itself on the 'live' side but I did not get any sign of a circuit (no light on the screw driver) on testing the neutral post of the heater. I thought maybe the power relay had something to do with completing the circuit to whatever heater was 'selected' on the timer.
I tried to put as much information as I could in my post so hopefully it would make some sense to you guru's!
I will try a stand alone supply to the pump to see if it shows any sign of life.
I have 'inherited' the problem heater from my daughter who has just moved into a flat and personally I have never encountered this type of heater before and you will easily gather I am not a professional electrician.
Hopefully I can get the thing to work as it does not appear to be a complicated piece of kit
Regards
Dave

Get a set of test leads.
Or a meter.
Test screw drivers are no good for this situation.
Mike

Hi Mike
Some success today. Bottom heater left on (for approximately 3 hours) until thermostat did its job and switched off supply, so system up to operating temperature. Pump ran on independent supply but would not start up on hot tap opening. So, I ran it again with an independant supply and opened a hot tap to 'prove' the heat exchanger. Water ran hot so no problem. Connected the pump back to system and put the power back on. On opening hot tap pump started this time and switched itself off a short time after tap closure.
The LED on the PCB gave some interesting indications after 'normal' for sometime. Firstly a T2 sensor fault, then back to 'normal' and at one stage constant flashing, which I think is a crashed microprocessor.
System then appeared to stabilise, PCB indication on constant 'normal' so I have left it on timer to heat on economy 7 overnight and will check it again tomorrow.
Maybe I have cracked it but not overly confident yet!
Thanks for your help so far and a great forum
Regards
Dave