Ruud U96VA0702317MSA Error Code 57: High Pressure Switch Open, Inducer on High Speed
What Does Code 57 Mean?
Code 57 on the Ruud U96VA0702317MSA means that with the inducer running at high speed, the high-pressure switch did not close, indicating insufficient draft for high-fire operation. A useful behavior of this two-stage furnace: if the low-pressure switch is still satisfied when 57 occurs, the control will drop to low-fire heat and keep running if it can, to try to satisfy the thermostat — so you may still get some heat.
This is a critical fault even though partial heating may continue. It is the high-pressure counterpart to code 45 on the low-pressure switch, and the opposite of code 55 (high-pressure switch closed with the inducer off).
The most common cause is a blocked or restricted vent — check the outdoor termination for obstructions — or vent length and elbows beyond the maximum. A faulty or disconnected inducer, disconnected or split pressure-switch hoses, or a faulty switch can also cause it. Restoring full high-fire capacity is a technician diagnosis.
What You'll Notice
- The furnace seems to run only on low fire and never reaches full output, with code 57 present
- Longer run times or trouble keeping up on the coldest days
- Possible signs of a restricted or partially blocked vent termination
- The fault may come and go as draft varies
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Vent blockage or improper termination | Most common | ✗ Call a pro → |
| Faulty inducer or pressure switch | Common | ✗ Call a pro → |
How This Is Diagnosed
Because vent restriction is the most common cause, a technician inspects the intake and exhaust for blockage and proper termination and confirms the vent length and elbow count are within spec.
They then check the inducer motor and wiring, inspect the pressure-switch hoses, and test the high-pressure switch, replacing whichever component prevents the switch from closing at high speed so full high-fire heating is restored.
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 runs only on low fire or struggles to keep up, with code 57 showing
- You find a restricted or blocked outdoor vent termination
- The fault persists after the vent termination has been cleared
Frequently Asked Questions
Why is my furnace only running on low heat with code 57?
When the high-pressure switch will not close at high speed but the low-pressure switch is satisfied, this furnace drops to low fire to keep providing some heat, which is why output feels reduced.
What usually causes code 57?
Most often a blocked or restricted vent, or vent runs that exceed the maximum length; a faulty inducer, hoses, or pressure switch can also prevent the high-pressure switch from closing.
✓ Verified against manufacturer service manual — March 2026