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Honeywell SV9540 Troubleshoot advice requested (NO HEAT)

Posted: Tue Dec 18, 2012 8:53 am
by chargedbird
Good Morning all,
I have a Honeywell SV9540 Gas Valve with the ST9160 Electronic Fan Timer. The T-Stat tells commands heat, I hear one realy click on the ST9160 and that is all. The start up fan does not come on and the ign. stays off, and I have a steady blinking light.

I do have 24VAC at the SV9540 on/off switch.
The AC Works
The Fan Works
The Fuse is good.


1. How can I prove all my safety switches are working?? (open or short)
2. Is there suppose to be any voltage going to the relay (black and white wire) on the SV9540 when the t-stat has heat command? (I have zero volts all the time, I believe this is my problem)
3. I checked all heat switches and they all read zero ohms (short) which is good.

Any and all information to help prove or dis-prove the GAS valve will be Greatly appreciated.

Thanks in Advance,

- Honeywell SV9540 Troubleshoot advice requested (NO HEAT)

Posted: Tue Dec 18, 2012 1:30 pm
by Freon
Google for Honeywell_SV9641M4510_Installation.pdf

The SV9540; SV9640 SmartValveā„¢ System Controls
combine gas flow control and electronic intermittent pilot
sequencing functions into a single unit. The low voltage
igniter, flame sensor and pilot burner are supplied by the
Q3450 or Q3480 Pilot Hardware. Provides all gas ignition
safety functions by controlling gas flow, ignition source,
and a 120 Vac or 240 Vac combustion air blower. The
control also monitors the appliance airflow proving switch
and limit string to assure proper appliance operation.
Provides prepurge, postpurge, timed trial for pilot igniton,
with 100 percent shutoff and continuous retry. Diagnostic
LED indicates system status.

You should have intermittent (spark) pilot light ignition. The pilot has to ignite (and be proven) before anything else will happen. The first click you hear in the gas valve is most likely the pilot part of the gas valve. Check that you have pilot light ignition. Then watch and see if it doesn't immediately turn off. If it does turn off, the flame sensor circuit is usually the problem. Cleaning the probe usually helps. Post the furnace model number.

- Honeywell SV9540 Troubleshoot advice requested (NO HEAT)

Posted: Tue Dec 18, 2012 2:24 pm
by chargedbird
Thanks for the info, I need to clear up something, the realy I hear is coming from the Electronic Timing Board (ST9162A). Sorry for the confusion. I DO NOT have any spark at all..nadda, nothing.

Here is what I have for a model - N T P - 6 0 5 0 F B G I

Ok, how can I prove or disprove the probe? What are the OHM readings

I have googled for two days looking for schematics and some kind of chart that explains what happens so I can figure out if its the GAS Valve or the Timing Board.

Thanks FREON!!!!


- Honeywell SV9540 Troubleshoot advice requested (NO HEAT)

Posted: Tue Dec 18, 2012 5:17 pm
by chargedbird
Update to make it clearer....I think

The induction motor is not turning on, and I have a steady blinking light on the Valve Board.

- Honeywell SV9540 Troubleshoot advice requested (NO HEAT)

Posted: Thu Dec 20, 2012 3:31 pm
by Freon
Without the inducer motor running and establishing the correct draft, you won't get spark. To test that the spark would work, TEMPORARILY jumper the pressure switch on the inducer circuit forcing the control board to think there is a good draft. If you see the spark then we know the inducer is the first problem to fix.

With a volt meter measure the voltage where the draft inducer motor plugs into the control board. When someone calls for heat you should see 120 volts AC. If you don't get 120 volts AC then I suspect the control board is the problem. If you see 120 volts then the inducer motor needs investigating.