RFSchaller
Well Known Member
My friend has an SLSA he is renting out. Recently a renter noted the Oil T and CHT going low off scale after takeoff. I gathered the following data today to offer up to the blog brain trust for comment:
I started the engine and observed all normal EIS indications so I warmed up the engine and did some full static RPM runs then reducing the power to idle. I noted that as the RPM dropped the main bus voltage dropped significantly and the CHT indications went into high alarm while the Oil temperature increased, but did not go into hi alarm. Next I slowly increased RPM to achieve a float condition (no charge or discharge on the battery) and observed the CHT and Oil temp decrease. Next I shutdown the engine and then turned on the G3X Touch: The CHT's indicated XX. I shutdown the G3X, waited about 4 minutes and turned it back on to see the CHT's in alarm. I have screenshots if someone wants to send me an email address.
Observations:
1. All indications seem normal for prestart and initial warm up.
2. The temperature indications appear normal when the battery is in a charging condition and high when the battery is discharging
3. The bus voltage is directly related to RPM, as expected.
4. Post shutdown the CHTs indicate invalid initially, but then return to on scale readings.
5. Only CHT and Oil temp appear erratic. Other EIS indications are as expected.
6. Gas tank level varied between 19 and 16 gallons during this data gathering period.
Comment: The CHT and oil temp sensors do not have dedicated ground leads.
Conclusion: The erratic indications appear to be limited to the Oil temp, CHT and Gas Tank level, and there appears to be a correlation to bus voltage/ battery charging state.
Any suggestions, guys?
I started the engine and observed all normal EIS indications so I warmed up the engine and did some full static RPM runs then reducing the power to idle. I noted that as the RPM dropped the main bus voltage dropped significantly and the CHT indications went into high alarm while the Oil temperature increased, but did not go into hi alarm. Next I slowly increased RPM to achieve a float condition (no charge or discharge on the battery) and observed the CHT and Oil temp decrease. Next I shutdown the engine and then turned on the G3X Touch: The CHT's indicated XX. I shutdown the G3X, waited about 4 minutes and turned it back on to see the CHT's in alarm. I have screenshots if someone wants to send me an email address.
Observations:
1. All indications seem normal for prestart and initial warm up.
2. The temperature indications appear normal when the battery is in a charging condition and high when the battery is discharging
3. The bus voltage is directly related to RPM, as expected.
4. Post shutdown the CHTs indicate invalid initially, but then return to on scale readings.
5. Only CHT and Oil temp appear erratic. Other EIS indications are as expected.
6. Gas tank level varied between 19 and 16 gallons during this data gathering period.
Comment: The CHT and oil temp sensors do not have dedicated ground leads.
Conclusion: The erratic indications appear to be limited to the Oil temp, CHT and Gas Tank level, and there appears to be a correlation to bus voltage/ battery charging state.
Any suggestions, guys?