HSI Resistance Conflict?


  #41  
Old 12-01-21, 03:45 PM
R
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 93
Received 4 Upvotes on 4 Posts
Originally Posted by roughneck77
Gas valve is absolutely not serviceable. But whatís wrong with yours? Is it delivering proper output pressure when energized?
It doesnít sound like a board issue either.
What else could it be?



 
  #42  
Old 12-01-21, 04:11 PM
R
Member
Join Date: Oct 2016
Posts: 2,135
Received 183 Upvotes on 169 Posts
If itís not lighting with a manual lighter itís something with the burner. What manometer are you using to measure pressure?
 
  #43  
Old 12-02-21, 07:42 AM
R
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 93
Received 4 Upvotes on 4 Posts
Originally Posted by roughneck77
If it’s not lighting with a manual lighter it’s something with the burner. What manometer are you using to measure pressure?
Yeah, that's part of the problem there too. My friend stopped by with his dad's manometer when I wasn't home -- he "says" he did the reading accurately and that it was 3.5. Which is the exact number listed on the sticker

But I'm not so sure about that. A decent manometer is btw $100 and $150 bucks and I'll never use it again, ever -- and can't find anyone to borrow one from. I'll make one from the link that @fastback provided but I just haven't had the time.

I think it's the board and/or the valve because the start-up sequencing is not consistent and the timing for the gas and the HSI seems to be off.


 
  #44  
Old 12-02-21, 01:32 PM
R
Member
Join Date: Oct 2016
Posts: 2,135
Received 183 Upvotes on 169 Posts
It still sounds like a burner issue. I doubt thereís an issue with the valve or board. You need to confirm gas pressure.
 
  #45  
Old 12-03-21, 12:58 PM
R
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 93
Received 4 Upvotes on 4 Posts
Originally Posted by roughneck77
It still sounds like a burner issue. I doubt thereís an issue with the valve or board. You need to confirm gas pressure.
Once it starts, the burners and gas stream looks perfect - no sign of low gas pressure or faulty burners - but yeah, I'm working on finding a manometer to borrow or build.

Plus, I've had the burners off the unit just this week to clean and inspect. Post #23 in this thread contains pictures of them, have a look-see - they're beyond perfect. Not a speck of dirt or debris in them OR the jets, which were also removed and inspected. Again, perfect.

I'm pretty convinced it's the valve. I looked at some details about this valve and I think there are 2 solenoids on it and the one that is supposed to fire first to start the unit, is the one having the issue.

And the fact that it struggles to start way more when it has been off for a long period of time, to me, screams valve. A corroded/faulty valve that is constantly opening and closing, struggles less than one that has been sitting.

I value your opinion, does that sound reasonable to you?



 
  #46  
Old 12-03-21, 01:06 PM
R
Member
Join Date: Oct 2016
Posts: 2,135
Received 183 Upvotes on 169 Posts
No it doesnít. If the valve is faulty there will be coil voltage but no output pressure. If thereís no output pressure the input needs checked as well, as it could be a supply issue.
Beyond that thereís really no usable data in this thread to present a diagnosis.
To add, if you replace the valve, youíll have to use a manometer to set gas pressure. You youíll be buying a manometer either way there.
You may be better off getting a service call done to assist with diagnosis. And then go from there for repairs.
 
  #47  
Old 12-04-21, 01:28 PM
R
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 93
Received 4 Upvotes on 4 Posts
Originally Posted by roughneck77
No it doesnít. If the valve is faulty there will be coil voltage but no output pressure. If thereís no output pressure the input needs checked as well, as it could be a supply issue.
Beyond that thereís really no usable data in this thread to present a diagnosis.
To add, if you replace the valve, youíll have to use a manometer to set gas pressure. You youíll be buying a manometer either way there.
You may be better off getting a service call done to assist with diagnosis. And then go from there for repairs.
I'm trying - I just took the voltage readings across the valve. For the first 10 no-ignitions, the reading was between 30 and 36 volts, then 'click' and the HSI shut off and the reading dropped to zero..

For the next 4, the reading was between 47 and 54 - then on the 15th try at 47 volts the furnace lit -- then the voltage dropped to 25.0 and remained there while the burners were flaming.

What does this tell you?


 
  #48  
Old 12-04-21, 04:00 PM
R
Member
Join Date: Oct 2016
Posts: 2,135
Received 183 Upvotes on 169 Posts
That would be impossible. The valve is 24V AC.
Those readings would mean the entire furnace control system was having major issues.
 
  #49  
Old 12-05-21, 07:32 AM
R
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 93
Received 4 Upvotes on 4 Posts
Originally Posted by roughneck77
That would be impossible. The valve is 24V AC.
Those readings would mean the entire furnace control system was having major issues.
So then, are you saying that I have a bad circuit board?

 
  #50  
Old 12-05-21, 08:39 AM
R
Member
Join Date: Oct 2016
Posts: 2,135
Received 183 Upvotes on 169 Posts
No, supplying that kind of voltage would cause damage to just about every low voltage part in the system.
I think you have meter issues.
 
  #51  
Old 12-05-21, 09:26 AM
R
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 93
Received 4 Upvotes on 4 Posts
Originally Posted by roughtneck77
No, supplying that kind of voltage would cause damage to just about every low voltage part in the system.
I think you have meter issues.
"Meter issues" as in the multi-meter I'm using?

Well, it's not the best unit but i don't think that's the issue - it's consistently accurate for every other task I ask of it. Even here, once the furnace starts, it's shows an accurate (within reason) depiction (24.4 to 25.0 Volts) of the proper voltage.

I was testing some more this morning and my probe was shorting the open blade in bay No. 2 with the brown wire connector on the next blade. The HSI glowed white, then meter showed 24.3 volts and immediately the furnace ignited. And this was after the furnace was allowed to get completely cold. So, I think/hope we might be narrowing this down.

If it's not the circuit board, I'm thinking the only other possibility is some sort of wiring short caused by a break or some corrosion. When I find the time, I'll clean al of the contacts and connections going from the board to the valve and see if I can't get 'er going.

Your take?

 
  #52  
Old 12-05-21, 11:00 AM
R
Member
Join Date: Oct 2016
Posts: 2,135
Received 183 Upvotes on 169 Posts
That still doesnít really give any usable data to determine the issue. The voltages you posted, donít even exist in any of the circuits in the furnace. So none of that makes any sense.
What is the amp draw of the HSI? And what is the voltage to it?
We also really need supply and manifold gas pressure.
 
Ratdude voted this post useful.
  #53  
Old 12-05-21, 11:48 AM
R
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 93
Received 4 Upvotes on 4 Posts
Originally Posted by roughneck77
That still doesn’t really give any usable data to determine the issue. The voltages you posted, don’t even exist in any of the circuits in the furnace. So none of that makes any sense.
What is the amp draw of the HSI? And what is the voltage to it?
We also really need supply and manifold gas pressure.
I'm seeing some old forums in a few places online where techs in the business are talking about this very scenario. Looks like in most cases it was brought on by shorts/faulty wiring but I noticed one or two where they replaced the board.

I haven't checked in a while but last I looked, this board was selling for around $175 - maybe it has come down in price but I'm thinking that would probably be too much to spend on this old furnace.

 
  #54  
Old 12-05-21, 11:50 AM
R
Member
Join Date: Oct 2016
Posts: 2,135
Received 183 Upvotes on 169 Posts
No, absolutely donít spend a dime on parts until you have the issue diagnosed. Youíll likely be out the money and still have a broken furnace.
 
  #55  
Old 12-07-21, 08:45 AM
R
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 93
Received 4 Upvotes on 4 Posts
RESOLVED: Circuit Board

I was able to get my hands on a used circuit board, screwed it in, moved all the wires over and the furnace now works perfectly.

Only thing is, reading up on 30-year-old furnaces and the transfer of deadly gasses into the ductwork thru hairline cracks in the heat ex-changer, I've decided to replace the furnace new anyway. No conclusive connection and I'm probably over-reacting here, but there have been a few headaches in the house lately and it got me a little worried - and I'm not really a worrier. I have CO alarms all over and none have indicated anything, but still.

So, the new furnace will be installed this week.

This was a learning experience - thank you @Pjmax, @user10 -- and @roughneck77 for hanging in there with me throughout. I really appreciate your help.



 
 

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