Howdy All,

Great forum!

I have a natural gas furnace with the Honeywell SV9541 2094 Smart Valve and ST9160B 1050 Fan Control Board.

We live in Wisconsin and it's summer here, so not much call for heat. But I changed the filter and like to test the furnace and A/C functions when I do.

The AC works just fine, no issues there.

When a call for heat is issues, nothing happens.

The light on the valve is solid green, no flashes.

I have the service manual and have looked at the electrical schematics and troubleshooting sections. This is what I've found:

1) The ignitor ohms out at 3.5 ohms across the blue wires.
2) 24 V is present on the Fan Controller Board 'W' and 'R' terminals. (Manual indicates this is the call for heat)
3) 120 V from the Fan Controller Board to the valve on pins 2 and 4 of plug C3.
4) No 120 V from pins 1 and 3 to the combustion blower when a call for heat is made.


Any ideas? I'm think the valve is bad?

Thank you very much for your time.
Brian

 

Failed control board is not sending power to combustion blower (inducer)

 

Thanks for the reply.

When I measure across Pins 2 and 4 at plug C3 on the valve, I get 120 volts.
Doesn't this come from the control board?

Brian

 

I have no idea... I don't have a schematic to look at let alone a furnace make and model number to try to find one.

 

I got the manual from here for the SV9541 Smart Valve with the ST9160 Fan Controller:

http://www.forwardthinking.honeywell...ll/69_2012.pdf

I'm looking at Page 7.

 

connector c1.... what is the voltage between 6 & 7 and 6 & 8 and 6 & 4?

 

Measurements between pins on C1:

6&4 = 14.8 V
6&7 = 28.0 V
6&8 = 28.0 V

 

I think you need 24V between 6&4.

 

Went looking for a description of what each pin should read as I waited your reply.

http://icpindexing.toddsit.com/docum...4008200102.pdf

Found this manual with a description on page 49. Am I reading it correctly that the voltage at C1 Pin 4 is the 1/2 wave rectified AC that will read 12 - 16 volts on most multimeters?

 

it says that is the same as P1 pin 5 which is 24VAC....

anyway there is no diagnostic for a solid green led on the valve is should be off, heartbeat, or flashing.... nothing for steady.....

I would try to jumper R to C1 pin4

 

HVACtech is right..Possibly you dont see it slightly flickering..(heartbeat)

And FYI smart valves are known to fail internally...The internal boards are crap...There is nothing good about a system with a smart valve IMO... The $$$ you will spend on repairing that best be spent on a new unit IMO..

You may be chasing ghosts.... And smart valves are like $400 bucks... I worked on many systems with smart valves..so just experience speaking....

How old is the unit???

Just saying is all... Dont want you to through good money after bad... Im sure HVACtech has worked on many himself...If so he may be inclined to suggest the same...

Good luck....And its good your starting now before the winter hits.....

 

Thanks for the responses, gentlemen. Your time is greatly appreciated.

lawrose - the unit is about 12 yrs old. I've looked at the valve in the dark, and I don't see any fluctuation in the light at all.

hvactechfw - I will give your suggestion a try. I was confused when reading the second manual, as I see where you point out that is said C1 Pin4 is the same as P1 Pin5, but C1 Pin4 is connected to P1 Pin2 in the schematic.

Thanks again, I'll posted back later today after work.
Brian

 

Gents,

I tried tapping R to C1 Pin 4. Nothing changed.

I'm also confused by the steady on Status LED. Does anyone know if it says on steady when there is no call for heat? Or is it supposed to 'heartbeat' all the time?
I can find that in the manual.

Thanks again,
Brian

 

I have the service manual in my hand... I will try to find online for you... My manual was given to me by AO smith when I was a rep...

Here is what it says on first page...

LED... bright-dim....normal operation...

Or heart beat as HVAC stated...

bright, dim, bright, dim....ect...

 

Ironically the two links that would have it on the service hand book for AO smith are corrupt and will not load...

 

Thanks lawrose.

I see the heartbeat indicated in the manual, I just can't find anything for a steady one LED.
I guess that makes me think the valve is bad, that and the fact it never routes the 120 to the fan.

 

Im telling you its the board inside... They crack... Its common... Additionally when they do sometimes the saftey by-passes and the gas valve opens when it should not...This happens before it proves a flame falure with the ignighter... Then the chamber fills with gas and it trys to relight...

BOOOOOOOMMMMMMMMM!!!!!!

12 years you got your moneys worth... I would replace.... You can maybe change the valve but what happens if the fan goes two weeks later, or it starts leaking......

New units are about $700 or so... You can get at your local Furguson dealer.....

Locations Finder

 

Time for a new gas valve.......

 

Gentlemen, I have a Comfortmaker furnace with Honeywell's SV9541 Smart Valve and during the inspection by my service provider I was told that the valve does not hold (close) the gas when the furnace does not call for gas. Does this happen a lot? The technician has connected some device to the valve test port to measure the pressure drop. It was dropping rather quick. He also had some sort of sniffer that indicated about 900 ppm of gas around the orifices when the furnace was not calling for gas. Should the smart valve hold the pressure for long? The servicemen told me that the valve replacement will cost $500 and the issue is with my both furnaces! Any comments would be appreciated.

 

Thermal i have the same issue!! And i cant find the right replacement part. Mine doesnt have a q or a m suffix. Did youhave any luck?

 

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