On a Daikin rooftop forced draft gas furnace with the RM7897A flame safeguard, flash code 2-2 (two fast blinks, then two slow blinks) means "Flame Signal Absent." Per Daikin IM 684-7 (May 2020), Table 7, the safeguard saw no flame at the end of the Pilot Flame Establishing Period, or lost the flame during the Main Flame Establishing Period or during RUN. The LED code repeats as long as the fault exists, and you clear it by pressing the RESET button.
How do you read the flash code on the RM7897A?
IM 684-7 (page 25) says the RM7897A has an LED to help diagnose burner operation, and that the fault is shown as fast and slow blinks. The fast blinks give the tens digit ("two fast blinks is 20") and the slow blinks give the units digit ("two slow blinks is 2"). Two fast blinks followed by two slow blinks is fault code 2-2.
The manual also says the flame safeguard switches to safety lockout and must be manually reset (page 15). If the pilot fails to ignite or the safeguard fails to detect pilot flame within 10 seconds, the burner is de-energized (page 15, sequence without MicroTech III; the MicroTech III sequence on page 13 says the same, followed by lockout requiring manual reset).
Which flash codes does IM 684-7 list?
This is Table 7 (pages 30 to 33), with the manual's own names and descriptions.
| Code | System failure | Description per IM 684-7 |
|---|---|---|
| 1-1 | Low AC Line Voltage | Low AC Line detected. |
| 1-2 | AC Quality Problem | Excessive noise or device running on slow, fast, or AC line dropout detected. |
| 2-1 | Unexpected Flame Signal | Flame sensed when no flame is expected during STANDBY or PURGE. |
| 2-2 | Flame Signal Absent | No-flame time present at the end of the Pilot Flame Establishing Period; lost during the Main Flame Establishing Period or during RUN. |
| 2-3 | Flame Signal Overrange | Flame signal value is too high to be valid. |
| 3-1 | Running/Interlock Switch Problem | Running or Lockout Interlock fault during Prepurge. |
| 3-2 | Running/Interlock On During Standby | Lockout Interlock powered at improper point in sequence or On in Standby. |
| 3-3 | VPS in Improper State | VPS (Valve Proving Switch) in wrong state during VPS Test. |
| 4-1 | Purge Card Problem | No purge card or the purge card timing has changed from the original configuration. |
| 4-2 | Wiring Problem/Internal Fault | Pilot (ignition) valve terminal, main valve, ignition or Main Valve 2 was on when it should be OFF. |
| 4-3 | Flame Amplifier Problem | Flame not sensed, sensed when it should be ON or OFF. |
| 4-4 | Configuration Jumper Problem | The configuration jumpers differ from the sample taken at startup. |
| 5-1 | Preignition Interlock | Preignition Interlock fault. |
| 5-2 | High Fire Sw. or Low Fire Sw. | Either High Fire Switch or Low Fire Switch failure. |
| 5-3 | Man-Open Sw.; Start Sw. or Control ON | Man-Open Switch, Start Switch or Control On in the wrong operational state. |
| 6-1, 6-2 | Internal Faults | Relay Module self-test failure. |
What does IM 684-7 say to check for code 2-2?
Table 7 (page 30) lists these checks for 2-2, in this order:
- Measure the flame signal. If one exists, verify that it meets specifications.
- Make sure the flame amplifier and flame detector are compatible.
- Inspect the main fuel valve(s) and valve connection(s).
- Verify that the fuel pressure is sufficient to supply fuel to the combustion chamber, and inspect the connections to the fuel pressure switches and make sure they are functioning properly.
- Inspect the Airflow Switch and make sure it is functioning properly.
- Check the flame detector sighting position; reset and recycle. Measure the flame signal strength and verify that it meets specifications.
- Replace the flame amplifier and/or the flame detector, if necessary.
- If the fault persists, replace the relay module.
On this furnace the flame detector is a flame rod, not a UV scanner. The manual refers to detecting flame "through the flame rod (FD)" (page 13).
What should the flame signal read?
IM 684-7 gives different flame signal ranges for different situations. Do not treat them as one number:
| Situation | Flame signal | Page |
|---|---|---|
| Pilot start-up | 1.5 to 5.0 volts DC | 11 |
| Modulating or multi-stage burner, pilot only, steady at low fire position | 2.5 to 4.0 volts DC | 16 |
| Single stage burner with no low fire start (always high fire), pilot only | 2.0 to 3.2 volts DC | 16 |
Page 11 also says that if the burner is equipped for modulation or two-stage operation, you should observe the flame signal reading at all firing positions.
What about 2-1, 2-3 and 4-3?
- 2-1, Unexpected Flame Signal (page 30): check that flame is not present in the combustion chamber, make sure the flame amplifier and flame detector are compatible, and if the code returns, replace the flame amplifier and/or the flame detector.
- 2-3, Flame Signal Overrange (page 31): make sure the flame detector and flame amplifier are compatible, check the flame detector sighting position, reset and recycle, and measure flame strength.
- 4-3, Flame Amplifier Problem (page 32): check wiring, remove the flame amplifier and inspect the connections, reseat the amplifier, and if the code returns, replace the flame amplifier and/or the flame detector.
Flame rod and ignition checks from the troubleshooting table
Table 7 refers to the flame detector but does not name a flame rod or ignition electrode check for these codes. The manual's separate troubleshooting table (Table 6, pages 26 to 29) does cover them under related symptoms:
- Pilot flame comes on, but the flame safeguard still locks out (page 27): the flame safeguard is not detecting pilot flame. One listed cause is a disconnected, shorted or open flame rod lead.
- Flame rod position (page 17): "Adjust the flame rod (see Figure 11)" and make sure the flame rod shaft is not shorted against the gun discs or pilot burner.
- Safeguard drops out as the spark comes on (page 29): one listed cause is ignition interference, where the flame rod or its wire is sensing voltage from ignition. The same row says to determine that the ignition electrode spark gap is within specifications.
- Ignition electrode position (page 16): the electrode tip should be centered within the 0.25 inch hole and be flush with the inside surface of the pilot burner or project up to 0.03 inches into the burner.
Our practical advice, not the manual's: a 2-2 that appears only at the start of a call can point at the pilot, ignition and flame rod, so those are the first things to inspect and measure. One that appears after the burner has been running can point at the gas supply, airflow switch or flame signal, so measure those first.
Parts involved
| Component | Role in this issue | Where to find it |
|---|---|---|
| Flame rod | The flame detector on this furnace. These are flame rod listings; confirm by unit model before ordering. |
059867701 — Flame Rod Replacement 036557700 — Flame Rod Replacement |
| Ignition electrode | Produces the pilot spark. This is an ignition electrode listing; confirm by unit model before ordering. | 059867801 — Ignition Electrode Replacement |
| Flame amplifier, relay module, airflow switch, fuel valves, fuel pressure switches | Named in the 2-2 checks. Match these by furnace model and serial number. | Daikin Parts for Daikin Applied, or request a quote |
Scope: This article covers the forced draft gas fired furnace FC ****A* with RM7897A flame safeguard as described in Daikin IM 684-7 (May 2020). The manual says the burner is designed for use with the furnace on Daikin rooftop heating and air conditioning units, and its Table 1 (Flue Height by Unit Model, page 5) lists burner models 020 to 200 with furnace outputs from 200 to 2000 MBH. It states that a forced draft design eliminates the need for draft inducers, so this article does not list inducer parts. Other furnace types and flame safeguards use different codes. The listed products are examples, not a fit confirmation.
Before you order
Read the rooftop unit model and serial number and the furnace or burner model from the nameplates. See Daikin Applied, McQuay, and Daikin-McQuay Part Numbers: Same Board, Three Names for how the part numbers relate, and browse Daikin Parts for Daikin Applied. Or contact us at help@totalhvacparts.com or 302-219-4994 with the unit model and serial number, the burner model and the flash code to request a quote and confirm fit.
Frequently Asked Questions
What does flash code 2-2 mean on a Daikin rooftop furnace?
Code 2-2 is "Flame Signal Absent" on the RM7897A flame safeguard. Per Daikin IM 684-7, Table 7, it means no flame was detected at the end of the Pilot Flame Establishing Period, or the flame was lost during the Main Flame Establishing Period or during RUN.
How do I reset a flash code on a Daikin rooftop gas furnace?
IM 684-7 says the LED code repeats as long as the fault exists, and that you clear the fault by pressing the RESET button. The manual also says the flame safeguard goes to safety lockout and must be manually reset. Find the cause first, because the code will return if it is still there.
What is the difference between flash codes 2-1 and 2-2?
Code 2-1 means flame was sensed when no flame is expected, during STANDBY or PURGE. Code 2-2 means flame was not sensed when it was expected, at the end of the pilot period or later in the cycle.
Does this Daikin rooftop furnace have a draft inducer?
The IM 684-7 forced draft burner uses a high pressure combustion air fan, and the manual says this eliminates the need for draft inducers, chimneys and draft hoods. Confirm your furnace type from the nameplate.
Sources
- Daikin IM 684-7, Forced Draft Gas Fired Furnace FC ****A* with RM7897A Flame Safeguard (page 25 flash code reading; Table 7 flash codes, pages 30 to 33; Table 6 troubleshooting, pages 26 to 29; flame signal ranges, pages 11 and 16)
- Live product titles for the parts listed above, as shown on each product page
Gas-fired equipment involves combustible gas, high voltage ignition and hot surfaces. Service should be performed only by qualified personnel, following the manufacturer's manual for your unit, local codes and your facility's lockout/tagout procedures.