Bad Gas Valve?

davej47

Here's my situation: I have a airquest 90% gas forced air system for heat and AC.  The heating unit is in the basement and the unit stopped working.



I got a trouble code on the unit of 6 flashes +1 flash which the manual says means:

Soft lockout: failed to light pilot during 90 sec. trial for ignition.



But that doesn't really match what I'm seeing.



If I cycle the main power switch so it powers up with a request for heat from the thermostat here's what it does:



Combustion blower kicks in

pilot valve opens (I can hear it) as the ignitor starts to glow

Pilot lights and the ignitor goes out. 

Pilot stays lit and then the main valve opens to kick in the main heating tubes.



They actually run for between 15 and 35 seconds but then , flame shuts off.  The system sounds like it's trying to restart, cycling what I assume is the pilot valve.  The ignitor will glow a few times (I think 3 times for 30 seconds each with a 30 second rest in between).  Then it goes into fault mode flashing 6 times then 1 as it goes through shutting down the combustion blower.



This cycle will repeat every 5 minutes.



I think it's the 'smart valve' going but I want to confirm this.  I can see that the ignitor works and that the pilot is working as well as the flame detector by it doing all of the early stuff.

I can't figure out why it's cutting out before the main blower kicks in (or maybe just as it is trying to kick in.)



Can anyone give me a set of tests to do in order to determine if it's the SV before I lay out $350 on one to get it overnighted to me?

It's a Honeywell sv9541m valve, single stage, If it's Discontinued what replaces this valve?

Thank you in advance for any help.

JUGHNE

Does it have a separate flame sensor rod and have you cleaned or replaced it?

davej47

Yes I replaced the sensor rod and cleaned the Drain trap

JUGHNE

Early Smartvalves had some problems. Even recall/replacements. Yours is probably out of that window.

Early problems were wire connection issues. Sometimes plug and unplug the molex connector will fix things.
Maybe someone here with more SV experience will jump in.

But if you order new, the model number must match original or the cross reference replacement.

davej47

yes the Date of Man. is 2004. I've already try'd unplug and replug, thanks for your advice,

Fred

Sounds like the flame sensor to me. Do all of the burner tubes light? I had a similar situation a few years ago, turned out to be a spider built a web in one of the burner tubes. Doesn't seem like that would block gas flow, but it obviously can.

HVACNUT

There's a Hot Surface Igniter that ignites a pilot light, then the pilot light ignites the main burners? I've never seen that set up.
After the main burners drop out and it goes into recycle, the HSI glows but no pilot? Is that right?
The proving of the induced draft by a pressure or centrifugal switch allows the HSI to power up. 115v I assume on that. What's controlling the operation of the pilot?

JUGHNE

Also, there are other simple things;
All flame sensors rely upon a good ground path to return it's signal to the valve/board. This may be thru the pilot tubing or a separate wire. If wire then the connections may need refreshed by disconnect/reconnect.

Pilot light must be clean, does it start to almost "wink out" as the main valve opens. If so then gas pressure may be low....this could be hit and miss for firing.

Then the pilot/flame is dependent upon the pressure switches remaining closed. If they open for a second the gas would drop out, but possibly the valve/board may not record that fault of failed air flow on exhaust blower.

davej47

pilot is lit at every start of operation, but main burner will no relight. also hot sur. igniter stays glowing red

davej47

new flame sensor, and all tubes are lit.

HVACNUT

Do you have a meter to check for 24v at the gas valve?
Does the pilot circuit also go to the gas valve?
Are the terminals like this on the gas valve?
MV- MV/PV- PV

JUGHNE

The brains for all of this ignition sequence is within the HW SV.

I have several items on my shelf with very minor wrenching marks on them from the try and test method. Several Ben Franklin bills sitting there. The cost of doing business.
If you were to have service person to fix this they might try the same thing that puts non-returnable items back on their shelves.

So are you feeling lucky??

davej47

yes I have a meter, I'll ck. for 24v. 3 connecters going to valve c1, c2, c3 3 wires, 4 wires, 8 wires. Don't see any ground wire from burner assy.

davej47

had a serv. tech come out and look at it, took 1 cont. test on pressure switch, said that was good, bad sv valve, and charged me 75 to look at it. wants 800 to change valve, and said it also might be ifc board at 500. lol

DZoro

Valve is not seeing the pilot flame, I would first change the pilot hot surface assembly, make sure to clean pilot. That series of valves are troublesome, clean each individual molex male and female sides. If still not working then change the valve.

unclejohn

Check the pressure switch. Or just replace it they are not at all expensive.

davej47

thanks everybody for all your advice, hopefully I can get it up and running without having to get a new valve.

Tim McElwain

When the pilot is up and running you need to check the microamps. Do you have the microamp adapter Honeywell Part number 395466? The igniter sensor is all one unit as I am sure you know. It runs 90 seconds then it will shut down for five minutes if the flame does not prove. The 90 seconds is actually broken down into 30 seconds on 30 off then 30 seconds back on. If the flame does not prove in that time it will go into the five minute shutdown.

What Electronic Fan Timer doe it have numbers please?

It sounds like you are having a combustion issue which is affecting the flame sensing and that is the micro amps. If the system is not running and the pilot flame is lit and the igniter is still glowing then that is a microamp problem not the gas valve Make sure you have a good burner ground connection..

davej47

ST9160B1084 Control Board Timer. no, I do not have the adapter. is there any other way of checking the micro amps?

Tim McElwain

No there is not. Your local Honeywell dealer can order you the adapter.

Does the system fan come on? It should come on in 30 to 60 seconds depending on the dip switch setting. Does this unit have an auxillary limit located in the blower compartment?

davej47

yes induction motor comes on pressure switch is closed . there is 2 flame roll out switches and a limit switch, all checked out to be working properly

mcfall

i have worked on lots of new efficiency units and sometimes it is just a simple problem overlooked by some techs.... if the exhaust fan vent is not aligned properly it will throw it into a lockout. drains can also be problematic. take the drain off at the unit to eliminate that. read the book about installing the vent and make sure it's correct. there are limits on the number of elbows and proper sizes of the pipe. has to be angled so many inches per foot. this causes condensation to run back down into the drain. put new battery in t-stat.

Tim McElwain

I was asking about the Blower Fan to move heat through the dwelling?

davej47

sorry, no, after trying to reignite 3 times, it goes I soft lock out, 6+1 flash's The unit worked flawlessly for 12 yrs..with the way its set up.

HVACNUT

I'm not familiar with Airquest.
Can someone explain why there is a pilot light AND an HSI and what is the benefit of having both?

davej47

HSI Ignites pilot, pilot heats flame rod, flame rod senses flame at a certain temp, returns signal to ifc to open gav valve for main burners. flame rod is 117-120 volts, pilot and gas valve is 24volts

ratio

It's IIRC a Honeywell SmartValve, has all the proof of flame integrated into the valve itself. HSI intermittent pilot with one wire to the valve.