Valiant chb problem

[Trance Nation]

Hi all.

I am having a bit of a nitemare task with a Valiant Thermocompact VU 182 E. Here's the story so far:
Customer reports intermittent fault with boiler lighting. C/H or H/W called for no ignition takes place, red lockout light comes on, customer resets and away it goes no problems till maybe 1 or 2 days later then same fault. Up until last week i had never actually witnessed any problems with the boiler and was merely taking an "educated guess" at parts, suspecting the usual faulty pcb, etc, but now know the boiler is not sparking when demand called for. Lockout occurs after approx 10 secs, reset the boiler and away it goes no problem for another day or so.

Parts fitted so far:

1. Both PCB's - Main one and the "other one !" (forget its name)
2. Air Pressure Switch - though i dont believe it was ever faulty.
3. Pressure Differential Microswitch/Diaphragm assy - aparantly last part req'd to operate before boiler sparks.

These parts were fitted over the course of the past year(ish) for different faults/reasons.
4. Detection Electrode
5. NTC Sensor
6. Fan assy - fitted November 2004 by another company

I have also checked the "bypass pipes" to the press. diff. switch and all is clear.

The customer mentioned to me today that the boiler only locks out when it has been off for long period - eg overnight. As i mentioned when it is reset it works fine till the next day or so then has to be reset again.

Im now thinking of possible circulation fault on the water side - maybe teh press diff switch is not activating till the pump is warmed up ?

Any ideas ? I dont fancy waiting on the phone for an hour to speak to Valiant tech help.

Cheers

 

[croydoncorgi]

Have you looked at the onboard diagnostics (eg d67, d68, etc.). There's bound to be extra clues there.

And I'm a bit confused about your reported symptoms. You say it's NOT sparking but goes to lockout after 10 seconds. Is the fan running during that period? Or does 'nothing' really happen?

 

[Trance Nation]

Have you looked at the onboard diagnostics (eg d67, d68, etc.). There's bound to be extra clues there.

And I'm a bit confused about your reported symptoms. You say it's NOT sparking but goes to lockout after 10 seconds. Is the fan running during that period? Or does 'nothing' really happen?

Sorry shouldve made that clearer :

Pump and fan both running - no spark. Lockout after 10 secs.
Reset and it works fine all day.

 

[mave]

It sound like the gas valve sticking. After it's been on it's seat for a while it sticks. Once it's been freed it will open and close OK until it is left for few hours, then it sticks again. Although it would be sparking if that were the case.

 

[croydoncorgi]

And the results from the onboard diagnostics?? (one of them is the total of successful ignitions after 2 attempts, for example.)

 

[chrishutt]

CC, I don't think this model has on-board diagnostics. As far as I can work out, the Thermocompact VU 182 EH is the system boiler version of the early version of the Turbomax VUW 242 etc., the one with the green knobs on black plastic background. Could the poster confirm this?

 

[Trance Nation]

Yeah thats right theres no on board diagnostics on this model (i was gonnae ask u about that !?). The boiler i would reckon is around 6 years old or thereabouts and yes its the one with the black panel/green knobs/led's at lhs.

I also had thought about the gas valve - wouldve been an obvious choice if sparking was taking place but its not so........

Any further ideas welcome - im popping back out to the job tomorrow anyway for a further investigation (that is if the snow doesn't stop me he he)

 

[idealmaint]

had the same problem last week. Someone had moved tghe boiler to another part of the house.
Worked okay on timed but if you switched it off for any period then it would lock out. Turned out to be the differential pressure switch. If you watched the switch it took forever to make and forever to break so if it was on timed the boiler still thought it was made but after it was switched off the boiler would lockout. Because the switch was partially made if you reset the lockout it would fire the second time with no problems