Lennox SL280UHV / SL280UHNV 80% two-stage variable-speed gas furnaces: quick sheet

Covers: Lennox Dave Lennox Signature Collection SL280UHV (and the later SL280UHNV / SL280UHNVK revisions) 80% AFUE two-stage gas furnaces with a variable-speed blower and a two-stage, variable-speed integrated control with a seven-segment display. Upflow or horizontal (left or right). Model examples printed in Lennox literature: SL280UH070V36A, SL280UH090V36B, SL280UH090V48B, SL280UH110V60C, SL280UH135V60D. Reading the pattern from those examples (not from a Lennox nomenclature table), the three digits after UH are the input in kBtu/h, the two digits after V are the nominal cooling airflow in kBtu/h (36 = 3 ton, 48 = 4 ton, 60 = 5 ton) and the last letter is the cabinet width (A 14-1/2 in, B 17-1/2 in, C 21 in, D 24-1/2 in). Search terms: SL280UHV, SL280UH, SL280UHNV, Lennox 280 two-stage. For the Lennox ML180/EL180 80% and ML196/EL296 condensing furnaces see the separate quick sheets.

Cross-checkedBrands: Lennox7 components

The SL280UHV is a non-condensing 80% furnace with two-stage gas heat, a variable-speed indoor blower and an integrated control that works either with conventional 24 V thermostats (set by DIP switches and clippable links) or with a Lennox communicating thermostat (all settings then come from the thermostat and the DIP switches are ignored). Diagnosis is done on the control's seven-segment LED, which shows status, target airflow and E-codes, and on a push button that opens the stored-code menu and a flame-current readout in microamps.

Safety first

Never jumper a pressure switch, limit or rollout.
E200 (rollout) and E241/E275 (flame out of sequence) are gas safety faults: shut down and refer to a licensed gas technician.
Gas valve, manifold pressure and burner adjustments are not covered here.

How it works

On a heat call the control proves the low pressure switch open, starts the inducer, waits for the low switch to close, heats the hot surface ignitor and opens first stage of the gas valve. Flame must be proven by the flame sensor or the control retries and finally goes into a soft lockout (E270).

With a two-stage thermostat (DIP switch 1 OFF, factory setting) W2 calls second stage. With a single-stage thermostat (DIP switch 1 ON) the control adds second stage after a timed delay set by DIP switch 2.

Lennox's 'watchguard' feature automatically resets an ignition lockout after one hour of continuous heat demand by breaking and remaking the demand.

If the low-fire pressure switch does not close in time the control may light on high fire instead (E229, information only). If airflow is restricted the blower runs in cutback and the control can lower the firing rate (E311/E312 warnings).

The control stores the last 10 codes in non-volatile memory, so they survive a power loss.

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Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Large stainless refrigerator set flush between kitchen cabinets by Alex Qian, Pexels License

Diagnostic guides for this appliance

Guide · Furnace

Furnace control boards: last-fault memory, fault recall and power-cycle rules (Carrier/Bryant, ICP, Goodman/Amana, Rheem/Ruud, Trane, Lennox)

Furnace boards show the current state on an LED or a 7-segment display, and many also keep a fault history. Some keep it only until power is removed; one Carrier-family description says stored codes clear on power loss or about 48 hours after the fault. Others have a fault-recall push button or recall terminal that replays recent faults. Read the LED through the door sight glass first; removing the blower door usually opens the door switch and drops power to the board.

7 steps ~15 mineasy

Guide · Furnace

Gas furnace fall inspection: what a handyman or appliance tech checks, and what goes to a licensed gas tech

Manufacturers and ENERGY STAR call for one professional heating check-up a year, ideally in early fall before the rush. The non-gas part of that visit (filter, airflow, condensate, venting condition, thermostat, blower and wiring, a supervised first fire) can be done and documented by a general tech. Anything that touches the gas valve, gas pressure, burner adjustment, combustion analysis or the heat exchanger belongs to a licensed gas/HVAC technician. This guide is inspection-only.

7 steps ~45 minmoderate

Guide · Furnace

Electric furnace or air handler with heat strips: fall pre-season check

Electric resistance heat has no burner or flue, so the fall check is about airflow, connections and proving every heat stage turns on. Measure supply voltage and the current of each element stage against the rating plate, look for heat-damaged wiring at the element terminals and sequencers or relays, and confirm the limits and blower work. Values come from the unit's rating plate and wiring diagram, not from this guide.

6 steps ~45 minadvanced

Other furnaces manuals

Manual · Furnace

York / Coleman / Luxaire TM9E 95% single-stage condensing gas furnaces: quick sheet

Johnson Controls (York) TM9E 95% AFUE single-stage multi-position condensing furnaces with a 5-speed standard ECM blower, 40-120 kBtu/h input. Model examples from the York technical guide: TM9E040A10MP12, TM9E060B12MP12, TM9E080C16MP12, TM9E100C20MP12, TM9E120D20MP12 (earlier ...MP11 revisions exist). Pattern: TM9E + input (040-120) + cabinet letter (A 14-1/2, B 17-1/2, C 21, D 24-1/2 in) + nominal airflow (10 = 1000, 12 = 1200, 16 = 1600, 20 = 2000 CFM) + MP + revision. Coleman and Luxaire sell Johnson Controls furnaces under their own names; confirm the model on the rating plate. The two-stage TM9V/TM9Y may show additional codes.

6 components4 common failuresYork, Coleman, Luxaire

Manual · Furnace

York / Coleman / Luxaire TM8E and TMLE 80% single-stage ECM gas furnaces: quick sheet

Johnson Controls TM8E (standard) and TMLE (low NOx) 80% single-stage multi-position furnaces with a 5-speed standard ECM blower, 40-130 kBtu/h. Model examples from the technical guide: TM8E040A12MP11, TM8E060A12MP11, TM8E080B12MP11, TM8E100C16MP11, TM8E120C20MP11, TM8E130D20MP11. Pattern: TM8E/TMLE + input + cabinet letter (A 14-1/2, B 17-1/2, C 21, D 24-1/2 in) + nominal airflow (12, 16, 20 = 1200, 1600, 2000 CFM) + MP + revision. Older TG8S and the two-stage TM8V are related families with their own literature.

4 components3 common failuresYork, Coleman, Luxaire

Manual · Furnace

Goodman / Amana GMVM97, GCVM97, AMVM97 modulating 97-98% furnaces: quick sheet

Goodman and Amana modulating condensing furnaces with a dual 7-segment display: GMVM97 (upflow/horizontal), GCVM97 (downflow/horizontal) and Amana AMVM97 / ACVM97. Goodman nomenclature: G (brand) + M (upflow/horizontal) or C (downflow/horizontal) + V (variable-speed ECM, ComfortBridge on newer units) + M (modulating valve) + 97 (AFUE class) + input (060, 080, 100, 120) + max airflow digit (3 = 1200, 4 = 1600, 5 = 2000 CFM) + cabinet letter (B 17-1/2, C 21, D 24-1/2 in) + N (low NOx) + revision, e.g. GMVM970603BN, GMVM971005CN. Older revisions are ComfortNet communicating; newer ones (2018+) use ComfortBridge with Bluetooth and the CoolCloud app. For the GM9S96 / GMVC96 see the separate quick sheet.

6 components4 common failuresGoodman, Amana, Daikin