Heil
Model # NUGK075DG08

I am stumped. Furnace was short cycling at first. Call for heat, Inducer motor comes on, Ignitor ignites pilot, Safteties all NC, Gas valve opens , burners lit, heat ing begins Blower fan comes on then roughly 1 minutes latrer kicks out on high limit. Found Dirty coil ,Dirty blower wheel, dirty secondary heat exchanger. Cleaned all look like brand new now. Drain clogged after cleaning flooding back into inducer motor wheel. Cleared the clogged line everything drained perfectly. Now cannot get unit to ignite . Does the Honeywell control box have to be mounted to ground it properly ?

All boards I am aware of need a good ground. Some controls have one or more of the mounting holes sleeved with brass. This is supposedly a source of grounding.

Ok the only thing I haven't done is mount the control box back to the unit. So this has to be my problem

Give it a try & let me know.

Ok so I mounted the ignition control box. Got ignition, pilot proved gas valve opened. When fan started gas shut off. Tested fan limit control and limit. Limit was faulty, so changed the limit and it worked perfectly.