Trane furnace E6.3: Igniter relay failed, or igniter open
E6.3 covers two possibilities that Trane lists explicitly: the igniter relay on the control has failed, or the igniter itself is open. One is a board fault and one is a consumable part.
Applies to: Trane and American Standard S9V2 two-stage condensing variable speed gas furnaces with a seven-segment integrated furnace control display, per Installer's Guide 18-CE01D1-1E-EN.
What it means
The control closes a relay to energise the hot surface igniter and monitors the circuit. E6.3 says that circuit is not behaving, and Trane names both ends of it rather than assuming. An open igniter is the far more common of the two — silicon carbide igniters are brittle, fail open, and are genuinely consumable parts that every furnace using one will need replaced eventually. A failed igniter relay is a control board fault and a much more expensive repair. The distinction matters commercially as well as technically, because replacing a board when the igniter was the problem is an expensive mistake in the wrong direction.
Most common causes
- A cracked or failed hot surface igniter, which fails open. This is the usual cause.
- Igniter wiring damaged, loose, or unseated at the connector.
- A failed igniter relay on the control board.
- Damage from previous service work, since igniters break easily when handled.
- An igniter at the end of its service life on an older furnace.
How to diagnose it
- Note whether the igniter glows at all during a start attempt, if the furnace has a sight glass.
- Note the age of the furnace and whether the igniter has ever been replaced.
- Note whether the fault began immediately after a service visit.
- The igniter should be measured before either it or the board is replaced.
How to fix it
- Technician work in the burner compartment.
- Ask that the igniter be measured first. It is the cheaper and far more likely of the two causes Trane names.
- A replacement igniter must be the correct part for the model.
- Only if the igniter measures good does the relay on the board become the suspect.
Notes
Because the code covers both a cheap part and an expensive one, it is worth asking explicitly which was measured rather than which was replaced.
Related
- E2.1 — Retry exceeded — flame never sensed, one hour lockout
- 9 flashes — Ignitor circuit problem, or low voltage between neutral and 24 volt common
All codes for this manufacturer
Trane and American Standard furnace flash codes — every code, with what differs between models.
What the fix costs
Trane names a cheap suspect and an expensive one, and the price gap is the reason to insist on measurement. The igniter: $150–350 installed per the igniter cost guide, with the universal silicon nitride part at $20–60. The relay: it lives on the integrated furnace control, so its failure means the board guide's $400–900 installed. An ohmmeter across the igniter settles which bill applies in under a minute, which makes E6.3 a code where "what did it measure?" is worth more than any second quote.
DIY or call a pro
The igniter guide makes the general case that a confirmed-dead igniter is one of the friendlier furnace repairs — but E6.3 is specifically the code where that confirmation is missing. The code itself cannot tell an open igniter from a failed relay on the board, and the test that separates them is a resistance measurement inside the burner compartment, beside the gas train. Replacing the igniter on spec risks a broken element and a wasted part to learn it was the relay. Have it measured first; if the igniter is the confirmed verdict, that guide covers the rest of the decision, bare-fingers warning included.
The same fault on other brands
Whether a control can tell its igniter from its ground reference splits the industry, per the igniter code hub. Trane's flash-code system cannot — nine flashes covers both. E6.3 sits on the clean side with York's twelve red flashes, open hot surface igniter, and the GMEC96-family board's twelve red, ignitor relay failure: codes that name the igniter circuit and mean it.
What this looks like
From the outside, this usually shows up as the furnace turns over but never lights — that walkthrough covers what to check in order, and when it stops being a homeowner job.