Ruud U96VA0702317MSA Error Code 55: High Pressure Switch Closed, Inducer Off
What Does Code 55 Mean?
A code 55 on the Ruud U96VA0702317MSA is a critical fault indicating the high pressure switch is in the closed position before the heating cycle begins, with the inducer not running. Like code 44 for the low pressure switch, this condition means the switch cannot be trusted as a safety verification device because it is reporting a closed state (meaning sufficient draft is present) when no draft has been created yet. The IFC checks both pressure switches before each heat cycle — gas heating is blocked while cooling and fan-only modes remain available.
The U96VA uses both a low pressure switch and a high pressure switch to independently verify venting at different thresholds. The high pressure switch requires a higher negative pressure to close than the low pressure switch. Finding the high pressure switch already closed with the inducer off indicates either mechanically stuck or welded contacts inside the switch, or an unauthorized bypass of the switch circuit. An abnormally high negative pressure already present in the vent system before the furnace starts is an uncommon but possible cause in unusual installations.
A technician must use a multimeter to test whether the high pressure switch contacts are physically stuck closed, inspect for any circuit bypasses, and check for unusual vent system conditions. A stuck or bypassed switch must be replaced or the bypass removed before safe heating can resume.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Pressure switch stuck closed or bypassed | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Call a technician to test the high pressure switch for stuck-closed contacts and check for any unauthorized bypasses of the pressure switch circuit — the switch must be replaced with the correct part if it has failed mechanically
- The technician should also inspect the vent system for abnormal conditions that could create pre-existing negative pressure without the inducer running
✓ Verified against manufacturer service manual — March 2026