Armstrong Ultra sx80 Honeywell?

[Colleenwalpert]

I have what is labled as an Armstrong Ultra sx80, I have found similar models labled "Honeywell" on the net.

My unit fires up fine. Gas, forced air. It will run for a very short while, when one of 2 electrial relays or the board (I can't tell which) makes a series of clicking noises and the unit shuts down. It is about 6 degrees under the hold temp currently, so it tries to fire up again... rinse and repeat...

Help!

Sorry, I left my camera at work or I would attach a photo.

Thanks!

[dkpd1581]

Your flame sensor my not be functioning correctly and shutting down the furnace.  The shut down will initiate a retry.

What kind of thermostat are you using - digital, old school bimetal mercury?  If it is bimetal, the heat anticipator may not be properly set.

[Colleenwalpert]

I took some steel wool to the flame sensor, and while doing so recognized this additional symptom:

When I apply pressure to the board on one of the two black switch boxes I can create the "clicking" noise and shut-down the system. If I play with it enough, I can get it to click on and stay on. I thought the problem went away until I reached desired temperature and the system shut down, never to start again. Bad board?

PS. I have a digital t-stat.

PPS. I had a great Lambic last night to ease my pain.

PPPS. Thanks so much for your help!