Honeywell 7800 Troubleshooting Guide

flame lost

Lock input disconnected

Accidental electrification of ignition transformer or pilot valve

The main valve terminal is not energized

Wind pressure switch disconnected

Blow card issue

Post Purge Stage 5.9

Locking conditions:

Guide valve or main valve terminals are energized

Internal malfunction or blowing card issue

Configurable jumper settings and locking risks

The 7800 series module is equipped with three field configurable jumpers (JR1, JR2, JR3), which are achieved by cutting the corresponding resistors. The module will lock the jumper state after the first 200 hours of operation of the main valve. Any subsequent cutting or restoring operation will result in an irretrievable lock (code 110), and the module must be replaced. Therefore, all jumper configurations must be completed during the installation and debugging phase (before 200 hours of operation).

The jumper function remains (uncut) and is cut off

JR1 first safety time (SAFETY1) 5 seconds 3 seconds (note: EC7850A1148/RM7850A1035 is 3 seconds → 2 seconds)

JR2 main flame test time 5 seconds 3 seconds

JR3 wind pressure switch without wind pressure switch (terminals 6-7 need to be short circuited) with wind pressure switch (short circuited 6-7 is prohibited)

Important: If JR3 is cut (with the wind pressure switch enabled), there must be no jumper wires between sub base terminals 6 and 7, otherwise the module will immediately lock.

Compatibility between flame signal measurement and amplifier

The 7800 series relay module is compatible with various flame amplifiers such as R7824, R7847, R7848, R7849, R7861, R7886, etc. The voltage range of the flame signal (between terminal F (11) and ground) is 60-220 Vac, with limited current. A high impedance voltmeter is required for measurement.

Common reasons for weak flame signals:

Flame detector lens contamination

The detector wiring is too long or the shielding is poor

Improper sensitivity setting of amplifier

Improper proportioning of burner air doors leads to unstable flames

Tip: KDM can be used to read flame signal intensity in real-time (displayed in microamperes or voltage values), making it a powerful tool for quickly diagnosing flame detection problems.

On site application of Run/Test switch

The Run/Test switch located at the top of the relay module is very practical for debugging and troubleshooting:

Switch position effect

Blow high flame stage → TEST stop blowing timing, maintain high flame position

Blow down low flame stage → TEST Keep low flame position

Guiding stable phase → TEST stop timer, allowing for guiding flame adjustment (activation of 15 second flame loss timer)

Operation phase → TEST drive adjustment motor to low fire position (EC/RM7850A only)

After completing the debugging, be sure to turn the switch back to the RUN position!

Common fault phenomena and troubleshooting ideas

Troubleshooting steps for possible causes of fault phenomena

The module has no response when powered on, the POWER LED is not lit, the power supply is missing, and the fuse is blown. Measure the voltage at terminal 5-2 (120V/220V); Check the external fuse

The lock indicator light is on, and the KDM displays an error code. The safety interlock is disconnected or there is an internal fault. Please refer to the KDM error code table (if code 110 is a jumper change lock, the module needs to be replaced)

The blowing fan does not start, and the pre blowing interlock is not closed or the wind pressure switch is faulty. Static inspection test 6: Short circuit 5-16 and 5-4 and measure the voltage at terminal 7. If there is no voltage, check the fan circuit

The ignition spark is normal but there is no guiding flame. The guiding valve is not open or the gas pressure is low. Static inspection test 8: Short circuit 5-8 and listen to the valve head action; Measure the voltage of the valve coil

Guide the flame normally but the main valve does not open. Main valve coil fault or wiring error. Static inspection test 10: Short circuit 5-9 and observe the action of the main valve; Check the voltage of terminal 9

Immediately lock the flame signal detection circuit after the flame is established, and measure the flame signal voltage if the amplifier sensitivity is inappropriate; Check the grounding of the detector; Adjust amplifier

During the MAIN DUAL phase, if the module is locked and the flame is lost or the main valve is not opened, check the supply pressure and valve position switch of the main valve; Confirm flame stability

Check the quality of the power supply for occasional and irregular locking of line noise, voltage drop, and poor grounding; Verify shielding grounding; Install line filter

Preventive maintenance and spare parts recommendations

To ensure the long-term reliable operation of the 7800 series system, it is recommended to:

Every six months: Clean the flame detector lens, check the insulation of the wires and the tightness of the terminals.

Every year: simulated flame fault testing (closing fuel valve, starting burner, verifying module locks within specified safe time); Clean the sub base pins.

Every 3 years: Replace the flame amplifier (if the model is discontinued); Update KDM firmware (if available).