johnson very abstract problem
I have this york/johnson rtu M#v33ad54a5idaaloo1, when the heat is enabled from main board to the modulating furnace control (staging relay control board), the third-five cell heat module creates a problem as soon as it goes for trial for ignition all stages of heat cycle off and code 8 is flashed on stages 2 and 3 (flame sensed with no gas), but when i disconnect power to the third Ignition control the first two stages work properly there is three total modules with standard two stage gas valves, the iginition controls are very standard with flame rods, Ive already replaced the modulating control board and problem still follows, ive made sure all wiring is correct and made sure ignition rod is not grounded, one thing i noticed is that there is no dedicated ground from mdp, but all of the piping is rigid to unit, i also checked voltage to chasiss and there is 277v to chassis incoming. 480 leg to leg, also all of the low voltage transformers are phased and wired correctly. i think it may be that i need a dedicated ground, any help would be fantastic!
Is the main modulating control board giving an error flash code at all, when this is happening? Make sure the Millenium/Simplicity parameters is set for 2 stages of Heat and not 3 stages. When the modulating board is installed must set staging for 2 stage. I think you will need the Simplicity program (free to download), but will need the FreeNet to USB adaptor from York/UPG to connect the Millenium board to your laptop to make certain parameter are correct, should be default 2 stage from factory though.
I would start there.
Have you swapped the number 3 ignition module with lets say number 1's module to see if it is the actual ignition module itself?
Not much more it can be...improper main board parameters and set-up, faulty main modulating board, faulty ignition module, or wire/harness issues.
Contact your York distributor for the FreeNet to USB and Programming Guide for the Millenium
Thinking about a similar 40 ton unit while watching Pawn Stars. I think you either have a bad ignition module for your 3rd stage or something is up with the wiring or harness between the ignition module and the modulating gas control board.
The main Millenium Board is pretty independent when it comes to the modulating gas option. It is just sending a W1 or W2 call to that board. The modulating gas control board is basing the stepping of each of the two stage gas valves for each of the three modules based on the input from the sensors. And the ignition control boards are independent of the modulating control board. So the system shutting down on flame present would lead me to believe that a faulty ignition module or wiring would be your culprit. I would assume in this case the modulating gas control LED is not blinking any suspicious errors only a quick 3 blink advising of a gas valve failure, which basically means that modulating gas control knows there is a call for heat and that the gas valve should be energized, since the ignition module locked out, it is not seeing that voltage.
Let me know what you find.
Here is a publicly available manual that outlines the programming, controls, etc. for the millenium control your unit should have:
thanks for the response, the millinium board is setup for 2 stage and the modulating furnace control is setup for 3 modules, it does indeed have three modules and the mfc board is not faulting any alarms, i've even swapped the ign modules from one to the the other and the problem still lies as soon as the third module is enabled (24v to w1 on ignition control 3) ive contacted york, they tell me the software setup only helps with accessing other parameters that have nothing to do with my issue, as long as 24v is present on w1 and w2 at mfc board the millinium is giving a heat call to mfc, and i have witnessed the 24 signal to mfc w1 and w2 at all times, i have also disected wiring to igc 1,2,3 and all wiring from mfc matches scematic and yes your right the mfc is the one controlller that dictates up to 17 different stage sequences, but the in this case when all stages are soppuse to be on, (all staging leds are lit) the igc's 1 AND 3 Fault out on code 8 this happends as soon as igc 3 attempts to light burner. tech support stated that it could be because of the lack of a dedicated earth ground and the rigid steel pipe is not suffecient, my plan is to go back and install ground and then maybe further tests.