What It Means
High secondary control voltage detected above normal range.
Rheem Furnace
Rheem Furnace Error Code 59
Troubleshooting guide for the Rheem Furnace system fault 59.
Possible Causes
- Transformer output voltage too high.
- Incorrect transformer wiring tap.
- Abnormal incoming line voltage.
Not sure which one it is — or if it's none of these? Try ACLogics today.
Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
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Full Diagnosis
High secondary voltage above normal range.
All Recorded Causes
Transformer output too high, incorrect transformer tap, abnormal line voltage, wiring issue, or control voltage outside the expected range. Verify against the exact unit manual.
Verify Before Replacing Parts
- Confirm the exact Rheem model family and furnaces context before acting on a generic code description.
- Start with line voltage, low voltage, and board output checks in sequence so the fault is isolated cleanly — the data plate flags transformer output too high, incorrect transformer tap, abnormal line voltage, wiring issu….
- Inspect connectors, relay outputs, and any recently replaced electrical parts for mismatch or loose fit, and verify verify against the exact unit manual.
- After the correction, run the system long enough to confirm the furnaces fault does not return under normal load.
Still unsure about this fault?
ACLogics walks you through Rheem Furnace diagnostics step-by-step — so you confirm the cause before swapping parts.
