[jjStar]

My Goodman furnace (GMP 100-5) usually give me some issues every year and I managed to learn/fix them during the past years.

This time, I thought I've narrowed this No-Flame issue down to a bad gas valve issue:

I got 24V reading on a multimeter after the Inducer was running, and the Ignitor was red-hot. (according to the operation sequence, after the Inducer is on, the Ignitor is on, the gas valve should open and I should've get flames.) -- I concluded the gas valve was bad.

So, I ordered a White-Rodgers 36G22-254 gas valve and replaced it. no flame. I guess I got a defective one. ordered another one from a different seller...

but still no flame...



Any Idea to troubleshoot/fix this issue?

(After the Ignitor is red-hot, I can hear the relay click sound for Gas valve is on, and I can feel a little vibrations with my finger. and I don't smell any gas at the mement. Yes, I have made sure there is gas flowing into the gas value: disconnect the gas valve and turn on and off the gas shut valve quickly. there's gas coming out with "pshhhhh" sound. )

 

[user_12345a]

Were you checking with both leads on the valve or referenced to ground?

Is there gas to the furnace?

 

[roughneck]

What’s incoming and manifold gas pressure?
Are you aware that the new valve will have to be adjusted to the proper pressure?
How are you checking voltage?
Have you checked the heat exchanger on that furnace? It’s known to have problems with heat exchanger cracks and crimp rings.

 

[jjStar]

Were you checking with both leads on the valve?
Is there gas to the furnace?

Yes. I am sure the gas flows to the furnace: I disconnect the gas valve, and turn on and off the gas shut valve quickly.

"referenced to ground" -- one of the 2 wires is grounded on the furnace itself. Not sure what I should check.

 

[user_12345a]

Need to see if the furnace is getting an adequate gas supply- could have a meter regulator issue in the meter.

Are there other gas appliances? Are they working properly?

Could be the valve is opening but the internal regulator is defective -> where did you source the valve? There are bad sellers on ebay and perhaps amazon too selling old junk as new or open box.

 

[jjStar]

What’s incoming and manifold gas pressure?
Are you aware that the new valve will have to be adjusted to the proper pressure?
How are you checking voltage?
Have you checked the heat exchanger on that furnace? It’s known to have problems with heat exchanger cracks and crimp rings.

I don't have an equipment to measure the gas pressure. Yes. I am aware of the need of the gas pressure adjustment. Would it be the issue I got: no gas at all? (I tried to smell close to burners. no gas smell)


This is the way I measured it:

After 10~15 sec the Ignitor was on, the meter showed 24~25 volts for 5~8sec. but no flame...

 

[roughneck]

Measure the voltage with the valve wired.
And check gas pressure. Improper valve adjustment can cause the burners not to light.
DO NOT try to smell gas or put your head anywhere close to the burners during ignition. Burners can backfire and have other problems that will send you to the burn center.

 

[jjStar]

Need to see if the furnace is getting an adequate gas supply- could have a meter regulator issue in the meter.

Are there other gas appliances? Are they working properly?

Could be the valve is opening but the internal regulator is defective -> where did you source the valve? There are bad sellers on ebay and perhaps amazon too selling old junk as new or open box.

My kitchen stove and water heater work fine. and also, in my attic, I can see my furnace and fireplace are shared with the same gas pipe. The fire in fireplace looks good too.

Yes. I was thinking the similar thing: so I order the 2nd one from a different seller. but still no flame.

 

[jjStar]

Measure the voltage with the valve wired.
And check gas pressure. Improper valve adjustment can cause the burners not to light.
DO NOT try to smell gas or put your head anywhere close to the burners during ignition. Burners can backfire and have other problems that will send you to the burn center.

thanks for the head's up. i won't do it again.... but... seriously, no gas smell.


"And check gas pressure. Improper valve adjustment can cause the burners not to light. " I probably need to get one of these then:
https://www.amazon.com/Hti-Xintai-Manometer-Pressure-Backlight-Included/dp/B07BDGWZLJ/ref=zg_bs_5006565011_1?_encoding=UTF8&psc=1&refRID=568KSYEDX0GHBPX5D5XZ

 

[roughneck]

Check the valve voltage with the wires attached to the valve first.

 

[jjStar]

Check the valve voltage with the wires attached to the valve first.

The wires with terminals has some plastic cover things. the probe leads can't reach to the wires..

Here is another guy doing the similar thing - https://youtu.be/9uhENM3nL-w?t=320
I'd guess the way I measured should be ok. no? What is different from measuring the volt while the wires are attached?


I also am struggling to make a decision: should I buy a 3rd gas valve...? maybe, the real issue is something else??

 

[user_12345a]

When there's an open circuit, you can get a normal voltage with a failing connection.

It takes current flow to produce a voltage drop.

 

[roughneck]

You’ll need to figure a way to wire the gas valve leads to the valve and be able to check the voltage.
Maybe buy smaller leads.
And you’ll also have to check gas pressure.
Don’t buy anymore parts without full diagnosis. The original gas valve could have been fine and not been the source of your problems.

 

[jjStar]

When there's an open circuit, you can get a normal voltage with a failing connection.

It takes current flow to produce a voltage drop.

Ok. then, does it mean the voltage reading would not be 24V with the wires connection on the valve, while the coil is engaged?

 

[user_12345a]

If there's a problem in the circuit, the voltage will drop when put under load.

If there isn't, it should stay roughly the same.

See if you can back off the connectors a little and expose some metal so you can check with the valve in the circuit.

 

[surferdude2]

Used a couple of straight pins to pierce the insulation.

 

[jjStar]

Thanks guys.

I got something:
I measured the voltage from one of the Rollout switches connecting to the gas valve (I believe it is for safety - the switch will break the circuit when the temperature is too high)

And it was 9~10 volts!!

Then I guess it could be some old loose connection issues again. Wag/Reconnect some connectors on the Control board. The gas valve was open and I saw the fire!

The voltage reading is 19~20 volts now, while the wires are attached to the GV. Would it be a potential issue here??


I think the connector design on the Control board is really bad. it is like this:
http://hvacrpw.com/icm280-furnace-control-board-for-goodman/ near the bottom left-hand side is connected to a wire harness like this http://www.waterheaterman.smugmug.com/photos/87066636-L.jpg

These loose connections caused me lots issues in the past. but I can't find a way to fix it. Any suggestion for this bad connection and where I can find a better replacement for these connectors? Thanks again.

 

[roughneck]

A GMP with a rollout switch problem?
Even being electrical in nature, I’d look really hard for rollout from the heat exchanger. Could mean the rollout has tripped a good bit in the past and is wearing out.
If the heat exchanger is cracked your furnace isn’t usable.
I’ve not had a problem with those connectors. If yours is loose your furnace could have excessive vibrations from something. And the clips should keep it tight.

 

[jjStar]

A GMP with a rollout switch problem?
Even being electrical in nature, I’d look really hard for rollout from the heat exchanger. Could mean the rollout has tripped a good bit in the past and is wearing out.
If the heat exchanger is cracked your furnace isn’t usable.
I’ve not had a problem with those connectors. If yours is loose your furnace could have excessive vibrations from something. And the clips should keep it tight.

no. I was not referring the rollout switch was having issues. I just used one of them to probe the voltage while the wires are connected to the Gas valve.


"excessive vibrations" <=== Right. the vibrations might cause the loose connection issue on my old wiring harness assembly. But the price tag for a new one is $91.00. It is way too expensive, I think.



The voltage I got is 19~20 volts when attach to the GV, and it's 24V when not connected to the GV ===> Is it normal?

 

[roughneck]

I’m not understanding.
Your not measuring across the switch? Your measuring from the switch to the gas valve?
That’s not how to troubleshoot your control system.
Measure across switches and loads.