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Carrier furnace with auto ignitor. Get error #34 ignition proving

failure. Ignitor lights & cleaned...
Carrier furnace with auto ignitor. Get error #34 ignition proving failure. Ignitor lights & cleaned sensing rod. Doesn't sound like gas is flowing. How do I tell if gas is coming through?
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Answered in 11 minutes by:
11/14/2013
Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3,971
Experience: Experienced in all aspects of HVAC, both residential and commercial.
Verified

Tim H. :

Hi, I'm Tim and I'm an HVAC expert here to assist you with your questions. Thanks for the opportunity to help!

Tim H. :

Hello there

Customer:

Hi, Tim

Customer:

You know anything about error #34?

Tim H. :

Yes, it is an ignition proving fault. Are burners lighting at all?

Customer:

I don't think so. The ignitor lights, but I don't think gas is flowing. I cleaned the sensor, but no change in amps across it when ignitor lights up. I'm assuming no flame.

Tim H. :

So burners do not light at all, even if only briefly?

Customer:

No

Tim H. :

Have you checked for gas flow to the furnace?

Customer:

Gas line also goes to hot water heaters and those are working fine.

Tim H. :

I would start by cracking a union close to the furnace and make sure it's getting gas. We can't assume anything.

Customer:

Ok, that will take some time. Let's assume gas is flowing. How do I check the gas switch mechanism that the gas flows into. It has an on/off switch.

Tim H. :

Make sure it has gas and that the on-off knob on top of the gas valve is in the "on" position. If everything looks good there, next step is to check for voltage at the 2 gas valve terminals around the time ignitor comes on

Tim H. :

We should have 24 volts AC

Customer:

Ok, if no 24ac then what? If we do have volts, then what?

Tim H. :

If you have voltage and good gas flow, then you have a bad gas valve. If no 24 volts anytime around the time ignitor comes on would signal a bad control board

Customer:

That's pretty much ends the troubleshooting I would assume. Is gas valve easy to replace? Just remove top & bottom connections and wires?

Tim H. :

Yes, fairly easy.

Customer:

I don't like working with gas. When I "crack" a union, what do I need to seal it back up?

Tim H. :

You just take 2 adjustable wrenches and turn the 2 halves just enough to hear if gas is coming out. Then immediately tighten them back up. You don't even need to take it totally apart.

Tim H. :

Unions are self sealing

Customer:

I'm not sure I have a union. I've got a ball valve. Out of that comes a flexible gas tube that runs into the unit and connects directly to gas valve. Can I just close ball valve and loosen connection to gas valve?

Tim H. :

Yes, you can do that and then briefly open the valve.

Customer:

Is there a special sealant, puddy I need to put in treads when reconnecting?

Tim H. :

Yes, if and when you install a new gas valve, use any standard pipe "dope"

Tim H. :

It's just to lubricate the threads

Customer:

Ok, but I don't need it if I'm just loosing connection & listening for gas?

Tim H. :

Most home improvement stores will help you with selecting a pipe dope. No, you don't need just to loosen and listen for gas

Customer:

In a nutshell, if burners don't light I've got

Customer:

1. gas blockage/no gas

Customer:

2. bad gas valve

Customer:

3. bad control board

Customer:

Anything else that I need to check?

Tim H. :

Absolutely correct! And we determine that by whther or not there is 24 volts AC to the valve or not

Customer:

got it. Thanks for your info. I'll go work on it and see. What do I need to do for you?

Tim H. :

Yes, good luck! Thank you for using Just Answer and please don't forget to rate my service. (Bonuses are always appreciated). Feel free to post back with any additional questions.

Customer:

ok

Tim H. :

Good luck

Customer:

Tim, are you there?

Tim H. :

I'm here

Customer:

Cracked union above gas valve. Gas was flowing.

Customer:

Ran unit. At rest, valve was reading 15V ac. When ignitor lit, valve read 28v ac. Assume bad gas valve.

Customer:

It's a white-rogers, but no marking on it. How do I know part #?

Tim H. :

Yes, if gas to valve and valve receives voltage and doesn't let gas come through, that would be a bad gas valve

Customer:

I took it off, btw. There is a gas manifold attached to bottom. Not sure how to take that off without bending it.

Customer:

I called local supply house. They won't sell to me...said I'd blow up my house.

Tim H. :

It should just unscrew from valve

Customer:

Any idea how to find PN?

Tim H. :

If you give me full model number, series number and serial number of furnace, I can locate a part

Customer:

ok, got to go look. hold, please...

Tim H. :

OK

Customer:

Bryant

Customer:

Model 373LAV048095

Customer:

Series G

Customer:

Serial 469A11644

Tim H. :

hang on....

Tim H. :

This should be the part you need, part# XXXXX

Customer:

Ok, thanks again for the help.

Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3,971
Experience: Experienced in all aspects of HVAC, both residential and commercial.
Verified
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Tim H.
Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3,971
3,971 Satisfied Customers
Experience: Experienced in all aspects of HVAC, both residential and commercial.

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