Clarifications on 172 panel L VAC R VOLTS

Question

dear all,

What is the meaning of this warnings?

I get them when I'm stopped and idle on the tarmac with engine on  

What shall i do?

Answer 1

Hi,

L VAC R means vacuum pump is weak, which is normal at Idle. The vacuum pumps is required for gyroscopic instruments (turn indicator and artificial horizon)

Volts in red indicates that the generator does not deliver enough tension, which is normal at idle too.

These indications are very realistic. If you add a bit of RPM (maybe 1700 RPM), they should disappear.

Best regards,

Guillaume