On Sun, 14 Nov 2010 14:04:33 -0800 (PST), wrote:

Hi;

I have a ruud furnace that wont stay running. The unit goes through
the start up cycle. The electronic igniter will start sparking, and
the flame will ignite. It will run good for about 5-7 seconds, then
it it will go out like the unit cut the gas off. I think it is a
flame sensor, but I am not sure what it is called.

This furnase has a circuit board with 3 leds. two are green and one is
yellow. It says Flame. This light flashes, but the other two stay
solid green. I cant find a manual to see how to read these. Any help
or pointers would be appreciated.

What you can do is find the flame sensor and clean it with fine steel
wool.
On this
http://www.acdirect.com/shop/images/..._448_Rev10.pdf
it's called "remote sensor" on page 2.
You might have to remove a plate/baffle to get at it, or just contort
your hand/wrist.

If that doesn't work, you might try a new flame sensor.
Bring your part AND your furnace model/serial number with you to the
HVAC supplier.
These things often have different parts than the drawings show.
After that I would get a pro in.

I went through this sensor cleaning, inducer diaphragm replacement
crap for years with my furnace after I had it installed.
Every damn season I had to tinker with it.
Hours of farting around.
Always guided by control board LEDs and troubleshooting charts.
Always got it going again, but never felt good about it, because the
problems seemed too random and flaky.
Even the control cycling would sometimes change - like the inducer
running for 20 seconds after shutdown, etc.
My wife hated that furnace, and I got to hating it too.
It's -20 out and you hear it try to start in the night and it has to
cycle twice to get going - you wonder if it will start.
Then it usually starts, but you lost an hour's sleep thinking about
it.

Then the main fan got stuck on low speed only.
I tapped around everywhere hoping to unstick what I supposed was a
stuck relay, then called a pro in.
The guy had the thing fixed it 10 seconds by twisting the control
board hard.
I agreed with him it would happen again and had him put in a new
control board.
ALL THE OTHER PROBLEMS WENT AWAY TOO.
We haven't given it a thought in about 4 years,
Best $470 I ever spent. The board was about $320.

Not saying what your problem is, and there's a couple things you can
do.
Clean/replace a flame sensor. Replace an ignitor/sparker.
New inducer diaphragm if indicated.
That's all inexpensive parts.
But if you have a flaky control board you'll spin your wheels.
I'm glad a relay got stuck on mine, otherwise I'd still be dealing
with that BS.
I used ServiceMagic.com to find my HVAC guy.
Think I'll mention that in a new thread.

--Vic