Domenick
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I've been helping a buddy troubleshoot his oil temperature system in a Piper Warrior II--not sure of the year. The results are baffling.
At operating temp in cruise flight, which we assume is 180F, the gauge reads about 95F with CHTs in the mid 300s.
Oil pressure is very good, very stable, near the redline in cruise flight.
The circuit is simple. Power comes to the gauge from the main bus, through a 5 amp breaker in parallel with the two fuel gauges. A single lead from the gauge to the probe, and the circuit grounds through the engine block. Fuel gauges behave well, but we don't know the resistance response of the sending units.
I derived the temperature resistance response of the Rochester 3080-37 oil temp probe.
Tests & results:
- Pulled the probe and tested its response from room temp to boiling with ohmmeter and digital thermometer. It behaved properly.
- Pulled lead off probe and grounded to probe body through various discrete resistors. Gauge read the expected temps.
- Continuity through probe lead verified.
- Continuity through ground verified.
- Grounded explicity with discrete wire from probe body to voltage regulator ground plate.
- Replaced probe lead connector.
- Replaced probe with new unit.
To us, these tests indicate the system is functioning properly, however it does not. With an oil temp of 180F the gauge reads 95F in cruise flight which indicates a spurious resistance of about 520 ohms.
I am looking for suggestions and comments. Thanks in advance.
At operating temp in cruise flight, which we assume is 180F, the gauge reads about 95F with CHTs in the mid 300s.
Oil pressure is very good, very stable, near the redline in cruise flight.
The circuit is simple. Power comes to the gauge from the main bus, through a 5 amp breaker in parallel with the two fuel gauges. A single lead from the gauge to the probe, and the circuit grounds through the engine block. Fuel gauges behave well, but we don't know the resistance response of the sending units.
I derived the temperature resistance response of the Rochester 3080-37 oil temp probe.
Tests & results:
- Pulled the probe and tested its response from room temp to boiling with ohmmeter and digital thermometer. It behaved properly.
- Pulled lead off probe and grounded to probe body through various discrete resistors. Gauge read the expected temps.
- Continuity through probe lead verified.
- Continuity through ground verified.
- Grounded explicity with discrete wire from probe body to voltage regulator ground plate.
- Replaced probe lead connector.
- Replaced probe with new unit.
To us, these tests indicate the system is functioning properly, however it does not. With an oil temp of 180F the gauge reads 95F in cruise flight which indicates a spurious resistance of about 520 ohms.
I am looking for suggestions and comments. Thanks in advance.
