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Billy
Billy, HVAC Technician
Category: HVAC
Satisfied Customers: 19661
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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I have a carrier furnace model 58GS that burners will not ignite.

Resolved Question:

I have a carrier furnace model 58GS that burners will not ignite. I am an electrician so I checked all the voltage outputs-I have 120volts to the furnace and 24 volts coming to the circuit board via the transformer. The pilot light ignites and I can see it sparking/hear it clicking to light the burners but they just don't come on. Any ideas? My furnace manual says replace the gas valve assembly? Thank you
Submitted: 9 months ago.
Category: HVAC
Expert:  Rick replied 9 months ago.

Rick :

Welcome, my name is XXXXX XXXXX I will do my best to help you with your issue.

Rick :

What are the terminal designations on your gas control valve? MV, PV, MV/PV?

Customer:

I have to go look at the furnace. I will be right back

Rick :

ok

Customer:

Where would this be located?

Rick :

Inside the burner compartment. The burner manifold is connected to the valve outlet and your gas supply line is connected to the inlet. One more question. Does the pilot electrode continue to arc even after the pilot is lit?

Customer:

Yes it keeps arcing after pilot is lit. It continually arcs and makes that "clicking" noise as if its constantly trying to light the burners.

Rick :

That's usually an indication that the pilot flame is not being sensed. On most versions of this model the electrode is also the flame sensor. You can try carefully cleaning off the oxidation on the electrode with fine sandpaper. With any luck this will solve the problem. If not you may need to replace the pilot burner assembly. I was asking about the gas valve terminals to determine if the board is sending 24 volts to open the main valve (24v across MV & MV/PV on many valves) if the pilot is lit the board is sending 24v to the pilot valve (PV & MV/PV).

Rick :

If the pilot flame is not being sensed there should not be 24 volts to energize the main valve which will let gas into the main burners so they can ignite

Customer:

Last night I did clean the electrode with sandpaper and no luck. My manifold has designations of 1 and 2 and 3 and 4 at the terminal connections. I dont see a MV or PV on the manifold. You are saying these letters would be on the manifold which is the same part where you can turn the dial to turn gas on and off-It is the part that has the gas supply in and out to the burners, correct?

Rick :

The terminal designation I mentioned is the most common current designation. But I don't know what you valve terminals are. There are at least a dozen different versions of your model furnace. If you have 24 volts across both pairs of terminals on you valve then that would indicate the valve (sounds like you found it, yes it has an On& Off dial) is faulty since it's being energized but given that the electrode is still arcing should be an indication that the pilot flame is not being sensed and therefore the main valve (which will let the burners fire up) should not be energized

Customer:

So I will check for 24v across the terminals on my manifold and if I have that then it still would not light because the pilot assembly is not sensing? Or my manifold could be faulty if I don't have 24 volts across the terminals? So I would replace the pilot assembly then?

Rick :

If you have 24 volts to both pairs of terminals then that's an indication the gas valve is faulty because it should open to let the burner fire up. You should now only have 24 v to one pair which is the pilot valve that opens to send gas to the pilot. Once the pilot lights the electrode should sense the pilot flame which should stop the arcing and energize the main valve. Since the pilot flame is apparently not being sensed there should not be 24 v to the main valve.

Customer:

Ok it will take me a while to check all this. Can I sign out and come back on later if I have more questions and it will still be included in the $30 fee or should i leave this page open and come back when I'm done?

Rick :

Since you cleaned the electrode and you still don't have the pilot flame sensed that's an indication that the pilot burner may be the problem. We would change the pilot burner when this happens. It's also possible the board is faulty but since the pilot burner is much less money than the board it gets changed first.

Rick :

This thread won't go away even after you rate me favorably. I will answer related follow up questions even after you rate me. You will only be charged when you rate me.

Customer:

So obviously I have to have the pilot light lit to test the 24v connections. Is it okay to be poking around with my tester while the gas and electricity is on to the unit? Sounds like a dumb question-being an electrician I know what I can and can't touch with electricity but when you add gas I get nervous.

Rick :

The only way you can trouble shoot this is with the unit powered up. Don't sweat the gas, your problem is that the gas isn't flowing. And unless you have a gas leak there's nothing to be concerned about. Can you tell me how many terminals on the gas valve again? I thought you said 4. Is that correct?

Customer:

Yes there are 4

Rick :

OK

Customer:

Oh wait there were 5 4 of them were the same size and the 5th one was "smaller" and was between 3 and 4 but let me go double check

Rick :

Ok, I'm going to hand this off to one of my colleagues who is more familiar with this gas valve than I am. He's online now and I'll send him a message to pick this up. Please be patient it may take a little while

Rick :

Please don't post again until you hear from hime

Expert:  Billy replied 9 months ago.
Hello,

Is this the 3 wire pilot with green, yellow and white wires?

And gas valve is numbered 1-5?

Billy
Customer: replied 9 months ago.

1 and 2 are on the right side of the manifold #1 has a white wire and #2 black wire- 3,4,5 are on the front of the manifold #3 is black-#4 is a smaller pronged connector than the others and is yellow- #5 is green

Expert:  Billy replied 9 months ago.
Thank you.

Get a short wire and shape in a U or use a jumper...

while pilot is lit.....jump gas valve terminal 1 to terminal 5 and tell me if burner lights.

Billy

Customer: replied 9 months ago.

ok be right back

Expert:  Billy replied 9 months ago.

Standing by

Customer: replied 9 months ago.

ok so the burners did light but only for a short period and then went out

Expert:  Billy replied 9 months ago.
Ok,

May be a domio effect or poor connection...but one thing is sure...the pilot assembly warp switch is bad.

Before moving on you will need to replace the pilot assembly.

EXAMPLE

1 to 5 bypassed the warp switch in the pilot. This was a common failure as the assembly aged.

Billy

Customer: replied 9 months ago.

ok so the pilot assembly is the piece that has the "sparking" electrode in it-correct? I will just have to find a place in madison thats open to sell parts today which is not likely.

Expert:  Billy replied 9 months ago.

Now that addresses the pilot warp switch...the constant sparking can be fixed by replacing the spark electrode in the pilot



It shuts down when it senses flame activity. Yours is older and just keeps sparking...it is not harmful just a nuisance

Customer: replied 9 months ago.

to remove the pilot assembly should i remove the gas tube that runs from the manifold from the part itself or from the manifold? I believe somewhere in my manual it says to remove it from the manifold but I can't find where i read that

Expert:  Billy replied 9 months ago.
With this unit there will be (2) 1/4" screws that hold a bracket (which holds the pilot) from the burner.

Unhook the 1/4" aluminum tube from the gas valve. Then the whole assembly comes out.

From that point you easily see how the unit is held to the bracket.

Remove tube from pilot. Pilot from bracket. Reassemble with new...

Billy, HVAC Technician
Category: HVAC
Satisfied Customers: 19661
Experience: Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
Billy and 3 other HVAC Specialists are ready to help you
Customer: replied 9 months ago.

sounds good- you have been so very helpful-Thanks again!!

Expert:  Billy replied 9 months ago.
You are very welcome.

I am available for 30 days after answer is rated so feel free to reply with any updates or questions.

Billy

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