Ruud U96VA0702317MSA Error Code 23: HALC Open
What Does Code 23 Mean?
Code 23 on the Ruud U96VA0702317MSA means the Integrated Furnace Control does not sense continuity between pins 3 and 5 of connector P1 — the High Altitude Limit Control (HALC) circuit. This furnace, as configured, does not actually include a separate HALC device; instead a jumper wire bridges those two pins. So code 23 almost always means that jumper has come loose or lost connection.
While the fault is active, the furnace will not provide gas heat, though cooling and fan modes still work. For safety, when the circuit opens the control energizes the indoor blower at maximum heating speed and de-energizes the gas valve.
The fix is to inspect and repair the jumper connection at connector P1 on the control board. Because that means working inside the control compartment on board-level wiring, it is a technician job rather than a homeowner repair.
What You'll Notice
- The display shows code 23 and the furnace will not produce heat
- The blower may run at high speed while the gas valve stays off
- Cooling and fan operation are unaffected
- The fault can appear after service work near the control board disturbed the P1 jumper
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Loose or disconnected jumper wire on connector P1 | Most common | ✗ Call a pro → |
How This Is Diagnosed
A technician inspects connector P1 on the IFC and confirms whether the jumper between pins 3 and 5 is present and making solid contact, since a loose or disconnected jumper is the usual cause of a lost HALC circuit.
They repair or reseat the jumper to restore continuity, then confirm the furnace returns to normal gas-heat operation. Board-level connector work like this is not a DIY task.
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 display shows code 23 and gas heat will not start
- The fault appeared after recent service near the control board
- The blower runs at high speed with the gas valve de-energized
Frequently Asked Questions
What is the HALC on my Ruud furnace?
HALC stands for High Altitude Limit Control; this furnace does not include a separate one, so a jumper wire completes that circuit on connector P1, and code 23 usually means the jumper came loose.
Can I reconnect the P1 jumper myself?
It involves working inside the control compartment on board-level connections, so it should be handled by a technician who can safely reseat or repair the jumper and confirm operation.
✓ Verified against manufacturer service manual — March 2026