My Smartfit room unit is showing no fault codes but boiler wont cut in I have no power at PL in control box or at L on boiler

Overheat Thermostat or thermostat sensor...

I am attaching the pdf document I found
(diagram on Page 30, items 16 & 17)...

http://www.freeboilermanuals.com/assets/pdf/baxi_disc/SOLO%203%20%2030-80PF%20SYSTEM.pdf

Several options... (most likely 71 & 72 ... Page 44)

Either unit could be defective... or legitimately REACTING
to a PUMP or FAN failure...
(or faulty wire to the control board)

The "LOGIC" on your control board is looking
specific temperature within a MINUTE...

Failing to see the Overheat Thermostat or
thermostat sensor... in a specific state ... the logic
will cut the fuel...

The "MANUAL" includes a trouble finding guide
(APPROXIMATELY after PAGE 44)...

Save the SWAPPED OUT PARTS AS GOOD SPARES
and buy yourself SPARE "sensors" so they will never
fail again).

Hope this helps.

Carnac the Magnificent

F04 is a fume thermostat fault

Is there an error code? If not the flow sensor for the hot water could be faulty. Also if you've had a power cut depending which model of Optimax HE you have, you sometimes have to tell the boiler it's a Combi, as they have a generic Pcb fitted which is also used on the system only boilers.

1. Switch off the machine, then switch on the machine.
2. Enter dC330 code 10-100 to heat the fuser to 180 degrees. Enter codes 10-200 (centre
thermistor) and 10-210 (front thermistor) to verify the condition of the thermistors.
3. Enter code 10-300 to check power supply unit 2. If necessary, install a new power supply
unit 2, PL 1.10 Item 4.
4. Switch off the machine. Remove the fuser assembly. Check that the thermistors, PL 10.25
Item 9 are clean and in good contact with the fuser heat roller. Check the wiring to the
thermistors. Install new components as necessary, PL 10.25.
5. Check for continuity between the two pins on the fuser assembly connector, PL 10.25
Item 8.
NOTE: A cold fuser has a resistance of approximately 11.5 ohms (220V/240V) or 2 ohms
(110V).
6. Check that there is continuity through the fuser heater and across the over temperature
cut-out.
7. Check the wiring between the fuser connector, PL 4.15 Item 20 and CON3, CON8 and
CON9 on Power Supply Unit 2. If necessary, install a new fuser connector, PL 4.15 Item
20.
8. Check the wiring between CON4 on Power Supply Unit 2 and CN7 on the Main PWB.
9. Install new components as necessary:
• Fuser assembly, PL 10.25 Item 1.
• HVPS, PL 1.10 Item 2.
10. Perform the OF5 Main PWB Check RAP.
4250/4260 Checkout
NOTE: The main PWB has test points. The location of the test points is shown on the Main
PWB PJ location illustration.
Refer to Wiring Diagram 17, Wiring Diagram 18 and Wiring Diagram 21. Perform the following:
1. Switch off the machine, then switch on the machine.
2. Enter dC330 code 10-100 to heat the fuser to 180 degrees. Enter codes 10-200 (centre
thermistor) and 10-210 (front thermistor) to verify the condition of the thermistors.
3. Enter code 10-300 to check power supply unit 2. If necessary, install a new power supply
unit 2, PL 1.15 Item 4.
4. Switch off the machine. Remove the fuser assembly. Check that the thermistors, PL 10.28
Item 9 are clean and in good contact with the fuser heat roller. Check the wiring to the
thermistor assembly. Check the wiring to the NC thermistor, PL 10.28 Item 19. Install new
components as necessary, PL 10.28.
5. Check for continuity between the three pins on the fuser assembly connector, PL 10.28
Item 8.
NOTE: A cold fuser has a resistance of approximately 11.5 ohms (220V/240V) or 2 ohms
(110V).
6. Check that there is continuity through the fuser heat lamps and across the over temperature
cut-out. Install new components as necessary, PL 10.28.
7. Check the wiring between the fuser connector, PL 4.15 Item 20 and CN5 on the Main
PWB. If necessary, install a new fuser connector, PL 4.15 Item 20.
8. Check the wiring between CON1 on Power Supply Unit 2 and CN7 on the Main PWB.
9. Install new components as necessary:
• Fuser assembly, PL 10.28 Item 1.
• Power supply unit 2, PL 1.15 Item 4.
10. Perform the OF5 Main PWB Check RAP

F4 code means that the control valve has jammed.

Go to honeywell.com
Under red welcome sign
Bottom red highlighted box literature/image search
Type in thermostat model number
Click on arrow to right
Then click on the PDF files owners manual / installation instructions
If you can’t find what you want, the bottom left and bottom of web
Page, they have homeowners assistance and Home products to get the help you need.

airswitch is faulty

Heya this is a manufacturing fault from honeywell them selves when it comes up -24 basically it needs to be replaced there is no way around in if you get in touch with honeywell they are generally good about it also if you provide them with the date code and model code they will be greatfull as it seems they have sent out a "bad batch". you locate this by:

A) Move the slide in to the off position
B) Press and hold i for 5 seconds
C) Unit will enter settings mode
D) Press and hold the i button and the + and ¿ button together
E) The unit will hold the relay on for 5 minutes and you can view by pressing the down arrow twice for model id/date code (ww/yy)

I hope this helps

I had exactly the same problem. F4 code says the control valve has jammed --- but it hadn’t.

I ended up having to swap out the room controller and the base unit (I bought the pair since it was winter and I couldn’t ‘eff’ about)

On investigating (well, you have to don’t you?) I could find no obvious fault but did notice that a large electrolytic capacitor was across the actuator motor.

Since these things work by reversing the supply polarity to the motor to drive the actuator one way and the other it strikes me as strange that a polarity sensitive component, one that must be always connecter positive to positive, is used in the way that it is.

Bottom line, tough luck, mate. Replace the units.

You could possibly have an ignition problem. The controller will go into a lock-out condition if flame is not established. Turning the temperature control down and then back up may be serving to reset the control system so it tries again.