# Gas Valve test?



## Yoyizit (Jul 11, 2008)

Measure voltage across, and current through, the valve.


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## trump (Oct 12, 2009)

how do you do that and what should they be at?


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## yuri (Nov 29, 2008)

What is the model # of the furnace and gas valve? I am a Lennox tech. Rapping the valve is not a great idea as sometime it may stick open and become dangerous.


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## trump (Oct 12, 2009)

Lennox G26Q 3/4 -125-1

Gas Valve VR8204H 2801

THanks!!


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## Yoyizit (Jul 11, 2008)

trump said:


> how do you do that and what should they be at?


With a multimeter, and then compare the values to the specifications for the valve [which seem to be hard to come by].
A Websearch on your valve part number may turn up a test procedure.

If it's a 24vac valve I have a procedure and circuit for testing that your transformer is up to snuff. The parts for this test circuit may cost ~$10 or so, so if in doubt you may want to just swap out the 'frmr.


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## yuri (Nov 29, 2008)

*"so if in doubt you may want to just swap out the 'frmr."*

Why not swap all the parts one at a time until you hit the right one? It should have a steady 24 volts to the valve.
Cozyparts.com for Lennox stuff.


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## Yoyizit (Jul 11, 2008)

yuri said:


> *"so if in doubt you may want to just swap out the 'frmr."*
> 
> Why not swap all the parts one at a time until you hit the right one? It should have a steady 24 volts to the valve.
> Cozyparts.com for Lennox stuff.


I should edit my posts more carefully.

I think there is value in reducing uncertainty no matter how cheap the part is, even if it means spending a few bucks and an hour or so making a resistor network. This becomes more true for HVAC people.

But, many DIYers would rather swap out inexpensive parts even if the likelihood of it being bad is low. 
In a way, it makes sense. It may be a poor bet, but they don't have much money & time riding on the gamble.

When the DIYer wants more certainty is when the part is very costly and likelihood of it being the root cause is unknown. Like replacing a part or replacing the whole furnace.

If there is 24.0vac across the valve and it doesn't work right, it is almost certainly the valve. But since current is what moves the valve I'd rather have a current reading and a voltage reading.
If it's >24vac, an open valve? Probably, since frmrs don't get 'stronger' and they usually have poor voltage regulation. Could also be a rusty connection.
If it's <24vac, a partially shorted valve winding or a 'weak' 'frmr? Which one?

If the OP does do the measurements, which one of these 3 readings and 5 possibilities will he/she find? Place your bets. 

Thanks for the parts link.


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## yuri (Nov 29, 2008)

I have worked on thousands of furnaces and only had 1 weak transformer. They don't get weak as all there is in them is 2 windings of different size and insulation. Capacitors are another story. Sorry to disapoint you but there are NO values anywhere for resistance of gas valve coils etc etc. Nobody wants or needs them. Techs isolate the problem and change the part, period. The only spec we need are flame current, gas pressures etc. Our industry is not an electronic fixable one with Radio Shack parts and telling posters stuff that won't solve their problem only leaves them without heat longer, Sorry. There are also safety and liability issues and I don't tolerate advice which can compromise that. Circuit boards have critical flame failure circuitry and a DIYer with a soldering iron/static discharge etc can damage that and cause danger, period. I admire you wanting to help though.:thumbup:


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## Yoyizit (Jul 11, 2008)

yuri said:


> Sorry to disapoint you but there are NO values anywhere for resistance of gas valve coils etc etc. Nobody wants or needs them.


With all due respect, how does the factory electrically test the parts coming off the assembly line?


Lemme' ask you and Beenthere a question. :huh:

I sometimes do extreme skiing in Canada and PA. :thumbsup: 

Some people cheer 
and some people hope I break my [email protected] neck. 

Which crowd would each of you be in? :confused1:


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## yuri (Nov 29, 2008)

Have no idea how they test them even if they do. My point is that not everything is on the net and searching for stuff that does not exist is futile. Hope you don't do a "Sonny Bono" someday. :laughing: We need interesting characters or the site gets too boring and I move on.


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## beenthere (Oct 11, 2008)

Yoz.

With EXTREMELY FEW EXCEPTIONS(the child murderers on the news as of late, are those exceptions). I never wish harm to anyone.
So I would not be wishing to see you break your neck..
However, maybe falling on your butt would be something I might wish for though. :laughing:

Kinda of like when I use to ride dirt bike. We always wanted to see one of us wipeout on a hill or jump. But never wanted anyone to get really hurt.
And seeing one of us get stuck in the mud boggs was always funny.

PS. Reading 24 volts across a valve, doesn't tell you if the valve is working or not.

Only tells you 24 volts is present.

Factory valve bench testing is easy. Input pressure on inlet side, Apply 24 volts, test for pressure on output side.


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## marchvac (Nov 29, 2009)

I would not recommend any diy to change out a gas valve. After the valve is in you must check for leaks, check the manifold pressure and also check temperature rise. That furnace I believe has a spark ignition and if it is the old johnson control it may not be operating correctly.


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## yuri (Nov 29, 2008)

Don't I know you from somewhere?? Hvacmechanic.com?


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## Houston204 (Oct 18, 2009)

That's what I was thinkin.


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## marchvac (Nov 29, 2009)

Hey Yuri and Huston how are you guys doing. Looks like you guys have everything under control. Ive been busy moving into a new shop.:thumbup:


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## Houston204 (Oct 18, 2009)

Yuri's been here a year, and I've been here since October. Are you still with a Lennox dealer?


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## marchvac (Nov 29, 2009)

Yes a commercial dealer. I also do large custom homes and service. I install ans service just about everything from fireplaces to millions of btu makeup air systems. By the way I know you are good with control wiring what do you think of the IAQ with the true steam. I put in a few and think there pretty good.


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## yuri (Nov 29, 2008)

Welcome Back!!! :thumbup: Our talent pool keeps getting better and better. Wish we could find your Ontario buddy TKG, I learned a lot from him and you and Houston.

Some people find the True Steam a bit small in large homes. Takes 4 mins to produce steam and in small homes the cycle could be 1/2 over by then. I have set them up with the IAQ system and G61's and like them. Need to clean the sediment out every yr.


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## beenthere (Oct 11, 2008)

Honeywell had a good idea. Until they made them in a 6 and 9 GPD model.

The 12 should be the small one.
And a 16 as the medium size and a 22 as a large one.


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## trump (Oct 12, 2009)

*more questions*

so i tested the voltage across the valve from the red to orange and have 24 v after the furnace tries and fails to light. Does this mean the valve is faulty. After a few min the furnace i assume goes to lockdown and i lose that 24 v. 

I shut off power and try again same thing happens 24 across the valve but then i traced the wires back and shook the re wire on control board a it fired right up so why if there was a loose connection would i still get 24v and the valve not operate?

thanks for all repys


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## beenthere (Oct 11, 2008)

Probably wasn't making good contact on the gs valve.
And when you shook it at the control board. it also moved at the gas valve. or you vibrated the furnace enough that it made better contact at the gas valve.


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## trump (Oct 12, 2009)

so if there is 24 v at the valve does this mean the valve is faulty?

i noticed i only have that 24 v when the valve is trying to open when it opens and the furnace is running there is 0. Is that normal.


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## beenthere (Oct 11, 2008)

Your not taking the reading right. Since it has to have 24 volts to stay open.

How many wires on your gas valve.


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## trump (Oct 12, 2009)

3 wires red orange and yellow i am reading across the red and orange wires it shows 24 from the call for heat until the flame kicks in.

red goes to 3 mv terminal
0range hooks with another and goes to pv terminal
yellow to ground

thanks again


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## beenthere (Oct 11, 2008)

Do you have a pilot burner, and a main burner.


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## Marty S. (Oct 31, 2009)

mv=main valve
pv= pilot valve
yellow is common
Should get 24 volts between yellow and pv first then 24 volts between yellow and mv. With voltage to mv and common you should have the gas valve open.


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## beenthere (Oct 11, 2008)

Your reading across the load wires to the valve when you check across red and orange.

You have to read to the yellow wire for each operation.


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## H. Phillips (Jan 5, 2010)

yuri said:


> . Sorry to disapoint you but there are NO values anywhere for resistance of gas valve coils etc etc.


If you have the amperage rating then you have the resistance value, you just need to do a little math. For example if a gas valve is supposed to pull .5A then the resistance is 48 ohms.


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## trump (Oct 12, 2009)

so i think i might have this narrowed down to possibly i have a faulty control. when the furnace fails to light i have no power at all from the control to the pv at the gas valve. if i shake the orange wire (pv) at the control the valve clicks on i have 24 v and the pilot lights . i have tried several times to clean and tighten the connection but it just doent seem to help so i am starting to beleive the problem may be in the control. Make sense to anyone? Also any good online sights i might find one it is a johnson G77 6RGD-2

thanks


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## SKIP4661 (Dec 3, 2008)

Change the pos blue johnson module with a Honeywell 53L90, problem solved.:thumbsup:


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## trump (Oct 12, 2009)

*more questions*

this morning i am leaning towards the problem being the ignition control module. if the furnace quits and it usually doeswhen trying to raise the heat form an overnight setting if i wiggle wires on the control it will kick in.

honeywell suggests a replacement #S8610U3009 for my old johnson control G77-6RGD-2 however when i look at the instructions for this honeywell that johnson number is not listed in what it replaces. 

anyone have any idea on whether this control might be faulty and or if this honeywell will work for replacement.

thanks
Trump


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## Marty S. (Oct 31, 2009)

cozyparts.com OEM part number 30W33


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## yuri (Nov 29, 2008)

The control IS faulty and order it from Cozyparts.com. Give them the complete model and serial # of the furnace. The new board will be a special S86 type and you need to follow the Lennox info exactly. The generic type won't give you very good conversion info.


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## yuri (Nov 29, 2008)

Good Morning Marty. Was just going to google Nebraska and see what your climate is like.


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## Marty S. (Oct 31, 2009)

Tropical compared to yours LOL


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## yuri (Nov 29, 2008)

Yah, but it is a Dry cold. Depends on what part of the State you live in. Weather like North Dakota in places, up to 3 feet of snow. I can relate to all of that. LOL.:thumbup:
Gotta get some Lennox stickers for the "company vehicle"


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