Ruud U96VA0702317MSA Error Code d6: Horsepower Conflict on Memory Card
What Does Code d6 Mean?
Code d6 on the Ruud U96VA0702317MSA is a memory-card mismatch: the horsepower the variable-speed blower motor reports to the Integrated Furnace Control does not agree with the horsepower stored in the model data on the memory card at connector P6. Because the copy of model data held in the board's microprocessor does match the installed motor, the furnace can keep running — so this is a low-severity fault.
Among the three card faults on this board, d6 sits between d1 and d4. Unlike d1 (no usable model data anywhere, furnace dead) and d4 (card unreadable but backup valid), d6 means the card is readable but its horsepower figure is simply wrong for the motor that is actually attached.
This almost always follows a recent repair: either the blower motor was replaced with a different horsepower rating, or the memory card or control board was swapped for one from another model. A technician should verify that the correct motor and the correct card are installed together, because a genuine motor/data mismatch can lead to improper blower operation and potential heat exchanger damage.
What You'll Notice
- The IFC shows d6 while the furnace otherwise continues to heat, cool, and run the fan
- The code appears shortly after a blower motor, memory card, or control board was replaced
- Airflow may seem normal because the board is running on its internal (matching) data
- The code persists until the correct motor-and-card combination is confirmed
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Blower motor or control board recently replaced with wrong part | Most common | ✗ Call a pro → |
How This Is Diagnosed
A technician reads the horsepower rating stamped on the installed blower motor and compares it with the model data on the memory card and the board. The goal is to find which part is the odd one out after the last repair — a wrong-horsepower motor, or a wrong card/board.
They then install the correct part so the motor and card agree, avoiding any card borrowed from another furnace or component, and cycle power to confirm the d6 notice clears with normal staging and airflow.
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 d6 notice appeared right after a blower motor, memory card, or control board was replaced
- You are unsure whether the installed blower motor is the correct horsepower for this furnace model
- The code persists and you want the motor-and-card match verified before further running
Frequently Asked Questions
Is it safe to keep running the furnace with code d6?
The furnace runs on the board's internal data, which matches the motor, so it operates for now; still, a technician should confirm the correct motor and card so the mismatch does not mask a wrong part.
What usually causes a horsepower conflict on this furnace?
It is almost always a recent repair where a different-horsepower blower motor was installed, or where the memory card or control board came from another model.
✓ Verified against manufacturer service manual — March 2026