Dick wrote:

Greetings all,

I have a Heil furnace that has a problem. I was hoping that someone
here could help me out.

The problem is the igniter sparks and lights the pilot and then the
pilot goes out right away. I spoke w/ a friend who is a HVAC tech and
he told me that it was most likely the flame sensor. Ok so I took the
unit apart and removed the igniter assy looking for a flame sensor. I
couldn't find one. The closest I can figure is that the igniter and
flame sensor are one and the same.

After I took the whole assembly out and cleaned it up per my friend's
instructions, it still didn't work. I used a fine emery cloth and
followed up by spraying the assembly w/ Zep Elec contact cleaner to
make
sure I flushed away any particles I may have created by sanding.

Tonight I turned the igniter 90 degrees in it's mount and voila, the
pilot stayed on for more than a second and the burners fired up.

The igniter unit has what appears to be a high tension lead going from
the end of it to a box made by Honeywell. There is also a grey ground
wire coming from the unit's mounting bracket that goes to the "ground"
terminal on the same box. That doesn't really make sense as the
furnace should be grounded anyway but that may there just for
redundancy.

The furnace was installed in 1992 or 1993. I don't know the exact
model of the furnace but in doing some research, I found a picture of
the igniter assembly online. It can be viewed he

http://www.expertappliance.com/heil-heating.html

It is about 1/3 of the way down the page and is called a "Pilot
Igniter Sensor"

The only way I can figure is that the Honeywell box sends out a high
voltage to the unit in order to fire the spark, and then waits for a
signal coming back on the same line telling the microprocessor that
the flame is present and it is okay to fire the secondary part of the
gas valve. The valve has three wires going to it and I figure that it
must be a two stage valve that fires the pilot at the first stage and
the burners at the second.

My questions is this. Is there any way other than just swapping parts
to determine whether it is the igniter/flame sensor assembly or the
Honeywell box causing me grief?


Any answers would be greatly appreciated.

Thanks in advance,

EBB

You're correct on all counts.

Do a GOOGLE for: Flame Rectification
for how they sense the flame.

It would take a very specific tester to check
sensor properties. Much easier to swap them out.

Jim