My York diamond 80 furnace does not start. Its message lights 3 times , so according to the table is the pressure switch. I can not find a diagram of the furnace. Where the switch is located?

FIRST turn off power and gas switch. Be Safe. I just removed the small hose (hose about 4-6 inches long.)from blower to switch at the blower end of hose, blew into and sucked back. You can hear pressure switch work. Then put hose back on. Worked Great... Hope this helps..

This worked for me as written.. Thanks A lot! I have a diamond 80 gas furnace. About 10 years old..

I have the same problem but the hose trick did not help. It just makes a humming sound. Any ideas?

We had a technician come out a couple of years ago for this problem and last year when the same thing occurred removing the tube and inserting paper clip to clean worked... Not this time!! The hint to blow into and suck out on the pressure switch was the key. It extended the time it stayed lit initially but still blew back out but I knew we were onto something. Did it a few more times blowing in for 10 seconds and sucking out for as long as I could. IT WORKED!! Thanks for the suggestion! You just saved us a weekend service call! Woo hoo!