Pilot won't consistently light - new components

Reply

  #1  
Old 04-14-20, 08:07 AM
N
Member
Thread Starter
Join Date: Mar 2006
Posts: 31
Received 0 Votes on 0 Posts
Exclamation Pilot won't consistently light - new components

I have a Bard furnace with Honeywell controls and propane gas. All electronic components working:
Thermostat calls for heat, inducer starts, 24v from S8610U control sends 24v to VR8345M pilot valve, good spark at pilot burner/igniter-sensor but pilot will not light 95-100% of the time. I used manometer to check house gas pressure, inlet pressure at the pilot valve - and even turned on all of gas stove's burners to ensure that gas pressure at the pilot valve still maintained pressure; and it did at 12" water column.
Had local contractor come yesterday to assess the problem. I was concerned about the 13 year old gas valve. He could not find anything else wrong and suggested that the gas valve might be weak and not opening the pilot gas enough, so he changed it out.
No change, still not working right. We know there is gas since while the spark is initiated since we can consistently manually light the pilot with a match. We made all kinds of adjustments (up and down) to the pilot flame after initial adjustment to spec. Once lit manually, the main valve will open and the furnace works to get up to heat setting. After shutdown, the next call for heat still will not work.
So all of that leads me right back to the Q345A (igniter) spark and gas area. The spark is strong. Is there ever a need to bend the flares of the Q345A in order to try to divert the pilot gas flow closer to the center, where the spark is?
Honeywell will not offer any advice on whether or not one of their other igniter/sensors (Q348, Q373, Q362) are comparable. They each have a slightly different design at the hood area.
I am hopeful that you all can help with this - and Thank You.
 
Sponsored Links
  #2  
Old 04-14-20, 11:55 AM
S
Member
Join Date: Oct 2013
Location: United States
Posts: 2,945
Received 41 Votes on 39 Posts
N,
I would look at the S86 module. You have 3 terminals on there that I would check since everything else seems to be working.

The terminals to check are PV, PV/MV, and MV. Mainly your PV/MV & PV. Your PV/MV is the common terminal of the 3. Make sure your connections are clean and tight. I believe you should have 24V between MV/PV & PV. If not you have a defective module.

These modules are are suseptable to just about everything from moisture to temp to life itself it seems and can be very irradic for no reason. I have changed them at times out of frustation like the problem you have even though it didn't point to that and it solved the problem.

Just my thoughts on the subject and a possible direction to go but that would be my bet. If you are going to have a company do this they should have one in stock and if it doesn't work they can reinstall the old one.

Hope this helps a little.
 
  #3  
Old 04-14-20, 02:31 PM
N
Member
Thread Starter
Join Date: Mar 2006
Posts: 31
Received 0 Votes on 0 Posts
Thanks "spott" but that module is not very old and it does test out perfectly with 24v headed to the ignition spark at the proper time. So I have spark and I have gas once the PV sends the 24v to the new gas valve and through the tube to the ignition area. Baffling - the service tech did not have any other idea of what to do next.

Thanks anyway.
 
  #4  
Old 04-14-20, 02:34 PM
N
Member
Thread Starter
Join Date: Mar 2006
Posts: 31
Received 0 Votes on 0 Posts
Sorry, I just re-read my response - second sentence should have said:

So I have spark and I have gas once the PV sends the 24v to the new gas valve, which opens and sends gas through the pilot tube to the ignition area.
 
  #5  
Old 04-14-20, 03:05 PM
S
Member
Join Date: Oct 2013
Location: United States
Posts: 2,945
Received 41 Votes on 39 Posts
N,
As long as the signal gets to the gas valve from the S86 it will work. The problem arises with that module when it becomes irradic, working when it wants to. It is basically just a circuit board and the module only as good as the soldered board. It may work 5 times and then not and when you reset it it make work again. You will get 24V to the module but may be a bad connection between PV/MV and PV terminals. It is very possible for your spark to be working flawlessly and your PV connection to be defective. All it takes is a bad solder connection or loose or bad wire.

When it doesn't lite do you have 24V from the module to the gas valve at that time or only when it lites. That module and the gas valve are the only things that light the pilot and you have already changed the gas valve.

Good Luck
 
  #6  
Old 04-14-20, 03:55 PM
N
Member
Thread Starter
Join Date: Mar 2006
Posts: 31
Received 0 Votes on 0 Posts
When it does NOT light, which is the case well over 95% of the time, it definitely has a solid 24v to the pilot valve, the spark is also solid, and the pilot gas has enough flow to light it with a match. On the rare occasion that it does light, there is no difference in the current from the S86 module, other than the flame sensor tells the S86 to send 24v to the main valve.
 
  #7  
Old 04-16-20, 08:48 AM
N
Member
Thread Starter
Join Date: Mar 2006
Posts: 31
Received 0 Votes on 0 Posts
I also posted this detail over on the HVAC forum. A few people tried to help over there but their policy is they will not help DYI'ers. I told them I have a heating and plumbing service provider do the work - like installing the new gas valve, but he could not figure out the problem so I was trying to do a bunch of research to find some help. Well, I guess based upon 1 guys comment about not helping DIY people, they killed the thread. I told him that I'm not a novice at understanding the concepts and principles - electronics, controls, gas - due to past experience on industrial furnaces. I also told him that it was me who troubleshot and discovered a bad component in the electronic control board when a different service provider could not figure it out. I told him I also know how/when to call in the professionals, but now was just trying to help - by gathering information.

I guess I'm done venting but I thought it odd when I was just looking for suggestions of what could be the problem - so that me and the service provider would know what direction to go next.

None of their suggested helped anyway.

Anyway, I now have it fixed and it has been working perfectly for 36 hours.



 
  #8  
Old 04-16-20, 12:06 PM
S
Member
Join Date: Oct 2013
Location: United States
Posts: 2,945
Received 41 Votes on 39 Posts
N,
I'm glad you got it working. I'm curious to know what the problem was.
 
  #9  
Old 04-17-20, 06:33 AM
N
Member
Thread Starter
Join Date: Mar 2006
Posts: 31
Received 0 Votes on 0 Posts
Ok, I'll share the solution with you.
All electronics were checked, pilot valve was old so it was just replaced. After that replacement, my service provider adjusted the pilot gas (after having to light it with a match) up and down a lot but could not find a place for it to light automatically, so after one of those sessions where it was match lit, he adjusted the flame to what looked appropriate per spec.
That's where it was left, which is when I started reaching out to you guys and others to gain more information. I even talked to Honeywell - who made all of my components; but nothing helped. So I knew I had spark at the proper time and I know I had gas.
Praying about a furnace problem might seem strange to you - but that's what I did. And then it occurred to me to do some very finite testing on the pilot adjustment. I started where it was left and started making small adjustments - opening the pilot valve a little more, retesting and then change more. Then closing the valve more and more; of course cycling the furnace after each change. After many, many of these changes, it finally lit on its own. I made an additional small adjustment - and it would not light. I returned it to the last prior position, and it's been lighting properly for 2 1/2 days.
So the summary is - the pilot was getting too much gas. Even though the flame looked to be the proper size with good color (when we were previously lighting with a match), it just would not light. So on this particular furnace with it's particular components, the pilot adjustment apparently has a very very small range where it will work. I just had to get there. And frankly, the pilot light now looks like it is too small to envelope the sensor - but I'm going with what works.
Sorry about the long story - but it's certainly not one I'll forget anytime soon. I hope it helps someone some day.
 
  #10  
Old 04-17-20, 11:38 AM
S
Member
Join Date: Oct 2013
Location: United States
Posts: 2,945
Received 41 Votes on 39 Posts
N,
Not too long. I enjoy reading about how problems get solved. I must admit however I must admit however that I never heard of too much gas to a pilot preventing it from lighting but if it's working now there must be something to it. Good thing you're persistant. Imagine paying a tech that amount of time to come up with that.

Happy Heating,
 
  #11  
Old 04-18-20, 06:06 AM
N
Member
Thread Starter
Join Date: Mar 2006
Posts: 31
Received 0 Votes on 0 Posts
You are right - about paying a tech. What I spent was too much as it was. But, since I told him what the final solution was, at least he has another "fix" in his bag of tools to help others - if he runs across this again. Come to think of it - he should have paid me. Oh well, at least my furnace has been working properly for 4 days now. We'll take that. Thanks.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: