[shblair]

My colman furnace seems to light up with the ignition properly... the flames are good for the prewarm period, then it clicks 3 times and turns off. I f this happens during the night, and doesn't come on... the small fan that removes unwanted gas before ignition is still running.
If I power off the furnace it will repeat the same series of events... if I unplug the wire that goes up to a diaphram like device (has clear hoses coming from it) it won't light the electronic ignition... plug it in and it repeats the same things.
Some times it does this all day 'clicking away' , turning off and back on again.
The ignition control is a Robershaw HS780... is this the faulty part?
My guess is this unit (HS780) is telling the gas valve to close prematurely.
Any input?
Thanks in advance.
Stu

[juggallojed]

My colman furnace seems to light up with the ignition properly....the flames are good for the prewarm period, then it clicks 3 times and turns off. I f this happens during the night, and doesn't come on...the small fan that removes unwanted gas before ignition is still running.
If i power off the furnace it will repeat the same series of events...if i unplug the wire that goes up to a diaphram like device (has clear hoses coming from it) it wont light the electronic ignition...plug it in and it repeats the same things.
Some times it does this all day 'clicking away' , turning off and back on again.
The ignition control is a Robershaw HS780...is this the faulty part?
My guess is this unit (HS780) is telling the gas valve to close prematurely.
Any input?
Thanks in advance.
Stu

Flame is not being sensed properly, check flame sensor and wires, also if the ground is corrupted it won't sense properly


I have had an occasion of the electric water heater elements partially grounding and causing voltage to go through the ground wire, this caused the symptoms you have described

I hope this has helped