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-   -   Ignition system starts, gas does not stay on? (http://www.diychatroom.com/f17/ignition-system-starts-gas-does-not-stay-31303/)

kkat69 11-06-2008 10:07 AM

Ignition system starts, gas does not stay on?
 
First time poster here hoping someone can help.

I have a Ruud HVac system (at work so I don't have numbers) in my attic.

The problem is, when it's time for the heater to kick in, I hear the click from the bedroom thermostat, I hear the inducer fire up, then I hear the gas ignite but it only lasts for a few seconds (not enough compared to the downstairs HVac) then after a while (the time it would normally take for the gas to heat up the air) the blower kicks on blowing cold air for a few mins, then the whole systems stops as if it's done it's job.

I'm thinking Flame Sensor but IMO that would stop the ignition sequence from continuing.

Also, FYI the system board was replaced earlier this year so that's brand new. As was the Igniter. I watched the process happen (and yes I have to basically shut the main switch to get it to happen again i.e., recycle power) where the gas actually ignites, but only lasts a few seconds.

Thanks in advance for any assistance/thoughts.

Marvin Gardens 11-06-2008 03:14 PM

I would be looking at the igniter and the flame sensor. Either could be bad.

Sometimes the igniter just looses it's power as the cap ages and just doesn't deliver a hot enough spark. Just because you can hear the igniter doesn't mean it is working.

kkat69 11-06-2008 04:01 PM

Quote:

Originally Posted by Marvin Gardens (Post 181320)
I would be looking at the igniter and the flame sensor. Either could be bad.

Sometimes the igniter just looses it's power as the cap ages and just doesn't deliver a hot enough spark. Just because you can hear the igniter doesn't mean it is working.


Thanks for the reply, I forgot to mention I replaced the igniter recently, it was cracked.

Also I watched the process, so I can not only hear but see the gas igniting then shutting off.

I'll see if I can edit my post to reflect this, but thanks for the vote on the flame sensor.

Marvin Gardens 11-06-2008 04:06 PM

Quote:

Originally Posted by kkat69 (Post 181340)
Thanks for the reply, I forgot to mention I replaced the igniter recently, it was cracked.

Also I watched the process, so I can not only hear but see the gas igniting then shutting off.

I'll see if I can edit my post to reflect this, but thanks for the vote on the flame sensor.

This is called rule outs. You consider the list of all the possibilities and then rule out each one either by logic or replacement.

We do this in the medical field all the time (although we don't replace often, just fix what we see).

dac122 11-06-2008 04:16 PM

Some temp sensors can be clean with emery cloth, and if you google around you might be able to find the ohm specs for testing. You might also have a high temp limit switch that is faulty. Look at your wiring diagram and see what other switches and sensors might be the problem and probe the ones that might be a possibility.


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