Ruud U96VA0702317MSA Error Code 23: HALC Open
What Does Code 23 Mean?
A code 23 on the Ruud U96VA0702317MSA indicates an open HALC (High Altitude Limit Control) circuit, which disables gas heating while allowing cooling and fan-only operation to continue. The IFC detects this fault when it cannot sense continuity between pins 3 and 5 of connector P1 on the control board. When the circuit opens, the blower motor runs at maximum heat speed as a safety response, and the gas valve is de-energized.
This furnace model does not have a physical HALC control device installed. Instead, a jumper wire connects pins 3 and 5 of connector P1 to permanently complete the circuit, because the same IFC board design is used across multiple models in the U96V series — some of which do require an actual HALC device at high elevation. On this model, code 23 almost always means the jumper wire at connector P1 has come loose, been accidentally removed during a service call, or has developed a break.
A qualified HVAC technician needs to access the IFC board, locate connector P1, and verify the jumper wire between pins 3 and 5 is properly seated and undamaged. Reattaching or replacing the jumper wire should resolve this fault immediately.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Loose or disconnected jumper wire on connector P1 | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Call a technician to inspect connector P1 on the IFC and reattach or replace the jumper wire between pins 3 and 5 — this is typically a straightforward repair but requires safe access to the control board
✓ Verified against manufacturer service manual — March 2026