vaillant turbomax plus 824e

lor · 16 Feb 2006

anyone familiar ?
do you know what voltage should be at the modulating solenoid as the max i get is 8 v dc. The reason for asking is i cannot get the boiler to run at full gas causing only warm water.bp 5.5 should reach 9.8mb.
inlet (working) 20mb
same on ch .if i push the centre of the solenoid in it reaches 9.8mb so suspect it is connected with the voltage.
a new pcb and thermistor made no difference.
please help as we have spent over 6 hours on it and are not charging
thanks alot

Gasman1015 · 16 Feb 2006

Are you Corgi.?

corgiman · 16 Feb 2006

sounds to like you need a new gas valve mate?

and possibly a new pcb, vaillant are great cos they say to fault find the problem test by substitution, so you end up replacing both cos the blooming stockist wont take them back after you have fitted them (esp the pcb!)

catch 22 thanks vaillant you are great

croydoncorgi · 16 Feb 2006

According to the Vaillant manual, you can read the modulator CURRENT straight off the boiler display (D37)
What I can't easily explain without looking at the boiler is why it's current rather than voltage, and what the possible value-range is.

Even so, if you look at the displayed value and see if it alters according to temperatures, etc. it might give you a clue what's going on.....

onion_soup · 16 Feb 2006

croydoncorgi said:
According to the Vaillant manual, you can read the modulator CURRENT straight off the boiler display (D37)
What I can't easily explain without looking at the boiler is why it's current rather than voltage, and what the possible value-range is.

Even so, if you look at the displayed value and see if it alters according to temperatur.....

Will this help with fault finding vrDIALOG 810 Diagnostic Software - Ref: 127896
from http://www.heatandplumb.co.uk/acatalog/gas_combi_condensing_vaillant_accessories.html

I did a search and Agile was interested in this last june ? did he buy one ?

It needs a rs232 port most laptops have usb , would a rs232 to usb converter work with this software ?

Agile · 17 Feb 2006

No I did not buy one because I did not know exactly what facilities it had.

The PCB probably actually measures the voltage across a series resistor. This is then called "current" as its proportional to the current. It is more relevant as measuring voltage would give a reading with an o/c coil.

I think that I have encountered exactly the same problem on a Vaillant while doing an LSC but was not being paid to investigate it further.

Tony

croydoncorgi · 17 Feb 2006

Will this help with fault finding vrDIALOG 810 Diagnostic Software - Ref: 127896

No - you don't need it. On the boiler quoted the diagnostic is built-in and you can read out the modulator current via the boiler's own LCD display. Whether knowing the current actually resolves the problem is another matter - but it should at least determine between PCB and gas valve faults.

Agile · 18 Feb 2006

Yes John, but do you know exactly what that software does?

As far as this fault is concerned it is an interesting one ( and I like those ).

The current in the mod coil depends on the applied voltage and the resistance of the coil.

If anyone can give me the gas valve model ( SIT 845 I think ) then I can advise what the usual voltage and resistance should be. I will need the additional figures from the valve and the mod coil colour ( blue ? ).

On those valves, if they are set for 1.5 mb min and 11 mb max then the applied voltage is 6v for 1.5 mB up to 11v for 11 mb. Above 8 mb its pretty close to 1 mB per volt !!!

Tony

cross thread · 18 Feb 2006

check jumper on pcb .drop flap and remove pcb cover(with power off !!)top left of pcb one small jumper.should be on left two pins if on right two it reduces output to modureg

croydoncorgi · 18 Feb 2006

Aha! Are these the 'gas valve selection' jumper(s)?
I heard of a large number of BG engineers going after the same fault after the first one had swapped SIT for Honeywell and not changed the jumper!
If either the gas valve or PCD has been changed (it has!) the jumper could be in the wrong position.
Nice one, gordongas.

lor · 19 Feb 2006

THANKS gORDANGAS

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vaillant turbomax plus 824e

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