Hartzell 5000k makeup air

[Backmtn]

Have run into a brick wall. The unit keeps tripping on pilot ignition failure. Have swapped Honeywell r7800 control with another unit. 3 new scanners( replaced as just in case) New transformer, ignition cable and ignitor. Cleaned grounds and have checked all wiring. Can never get unit to trip while on site, 24 hours so far of watching on a cold roof. All gas pressures are at manufacturers specs. Can't get any help from Hartzell rep, or factory. 12 year old unit is considered obsolete. Any ideas more than welcome.

[Mihvactech]

What's your flame signal during pilot establishment ? Dirty pilot ?
Flame proving location/condition ? Pilot size ? Burner ground if using flame rod

[Mike Doran]

cracked plastic mounting block under 7800n control??? found one recently where the plastic on the base of the control was broken and the connection inside the base was not lining up properly and boiler kept locking out on flame fail. just another thing to check

[Backmtn]

What's your flame signal during pilot establishment ? Dirty pilot ?
Flame proving location/condition ? Pilot size ? Burner ground if using flame rod

Perfect 5vdc on ignition through main flame, pilot is beautiful, about the size of 2 golf balls and blue. Thank You for the ideas

[Backmtn]

Thanks for the idea, I will check that tomorrow morning. The unit does have a very high vibration with the prop fan. I'll let you know how I make out. Thanks again for the input.