Trane · Furnace

E7.2 Redundant relay (HLO output) on with no call

Critical severity Trane S8V2

What the control is telling you

The IFC high limit output relay is stuck on.

Applies to: Trane S8V2 only

Likely causes

Failed relay on IFC
Wiring back-feed on HLO

Test and repair steps

Turn the thermostat to OFF.
Measure from HLO to common nominal 24 VAC means the output is on when it should be off.
Check for field wiring feeding HLO; if none, replace the IFC.

Settings for these units

Clearance to combustibles · Trane S8V2

Cabinet width	Vertical sides / top	Horizontal sides / top
14.5 in.	0 / 1 in.	1 / 2 in.
17.5 in.	0 / 1 in.	1 / 2 in.
21.0 in.	0 / 1 in.	1 / 3 in.
24.5 in.	0 / 1 in.	1 / 5 in.

24 in. front service access.

3 in. in front of the combustion air openings.

Return filter size by cabinet width · Trane S8V2

Cabinet width	Filter
14-1/2 in.	1 - 14 x 25 x 1 in.
17-1/2 in.	1 - 16 x 25 x 1 in.
21 in.	1 - 20 x 25 x 1 in.
24-1/2 in.	1 - 24 x 25 x 1 in.

Filters are field supplied and mounted outside the cabinet.

Over 1600 CFM upflow: return on both sides, one side plus bottom, or bottom only.

Models that show this code

12 models in Trane S8V2

S8V2A040M3PCBS8V2A040M3PDS8V2B060M4PCBS8V2B060M4PDS8V2B080M4PCBS8V2B080M4PDS8V2C080M5PCBS8V2C080M5PDS8V2C100M5PCBS8V2C100M5PDS8V2D120M5PCBS8V2D120M5PD

Other codes on the same units

E6.1 120 V polarity reversed
E6.2 Ground not detected
E6.3 Igniter open or igniter relay fault
E7.1 1st stage gas valve (MVL) powered with no call
E08 Low flame signal (still running)
E11 Gas valve relay / valve circuit fault
E12 Control fuse open
E13 Blower motor size / OEM ID mismatch

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Source: Trane FNR-SVX003A-EN (S8V2 installer's guide) - section Integrated Furnace Control Display Codes, Table 37 Error codes; Trane FNR-SVX003A-EN (S8V2 installer's guide) - section Troubleshooting (flowcharts). Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.