Rheem R96VA0702317MSA Error Code 46: Low Pressure Switch Open, Inducer on Low Speed

What Does Code 46 Mean?

The Rheem R96V is a two-stage condensing furnace, so it can burn at high fire or low fire. It always ignites at high fire with the inducer at high speed, then, once the heat demand can be met at a gentler rate, it steps down to low-stage heating and slows the inducer to low speed. At that lower speed the induced-draft motor develops less negative pressure, but the low pressure switch must still stay closed to prove the reduced draft is adequate. Code 46 means that after ignition, when the furnace switched the inducer to low speed for low-stage heat, the low pressure switch opened instead of staying closed.

Because the furnace never ignites at low speed, code 46 should only ever appear after a successful high-fire light and after the blower-on delay, at the moment the furnace transitions to low stage. That timing is the key difference from code 45, where the same low switch fails to close at HIGH inducer speed before ignition. In code 46 the furnace already proved draft at high speed, so the trouble shows up specifically at the lower draft of low-stage operation.

The most common cause is still a restricted or improperly terminated vent, since a partial blockage may pass enough draft at high speed but not at the reduced low-speed draft. Vent runs that are too long or have too many elbows for the model's specification behave the same way. Importantly, at higher elevations the air is thinner and the low-speed draft margin is smaller, so a missing or incorrect high-altitude kit is a recognized cause on this model. A weak inducer or a marginal switch can also produce it.

A homeowner may visually check the outdoor vent terminations for ice, snow, debris, or nests as an observation, but the hoses, inducer, switch, and any high-altitude kit changes are technician-only on this sealed furnace.

What You'll Notice

• The furnace lights and runs on high fire for a short time, then shuts down as it tries to settle into low-stage heat, with the display flashing 46.
• Heat cycles feel short: the burners come on but the furnace cannot sustain the quieter low-fire stage.
• The problem is more noticeable at homes located at high elevation.
• The outdoor exhaust or intake termination shows partial blockage from snow, debris, or a nest.
• Cooling and fan-only modes continue to run normally.

Common Causes

How This Is Diagnosed

The technician works through the draft path in the sequence the fault occurs. They confirm the furnace ignites normally at high fire, then watch the transition to low-stage heat where the inducer drops to low speed and the code appears. They check the outdoor terminations and the full vent run for restriction, excess length, or too many elbows, then inspect the pressure-switch hoses for splits, blockage, or condensate. They compare the low switch's continuity against the actual draft measured at low inducer speed; if the low-speed draft is marginal the fix is in the venting or inducer, and if strong draft is present but the switch opens the switch is condemned. At elevation the tech verifies the correct high-altitude kit is installed for the site. Throughout, they confirm they are evaluating the low switch at low inducer speed, distinct from the low switch at high speed (code 45) or the high switch (codes 55 and 57).

When to Call a Professional

This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:

• The furnace lights on high fire but shuts down every time it tries to switch to low-stage heat.
• The home is at high elevation and 46 appears, suggesting a missing or incorrect high-altitude kit.
• The outdoor vent terminations are clear but the code returns on the low-stage transition.
• Heat cycles are repeatedly cut short even though the burners initially light.

✓ Verified against manufacturer service manual — March 2026