Got the plane back and went flying today

[allen]

So I get the plane back and go up for a short flight in the pattern. After I’m up in the air I noticed that my EI Tach is working fine, but is no longer reading “Tach Time”.  Seems like each time I take my plane to these guys they give it back with something new no longer working. Frustrating.

My question is do you need a tach time and a Hobbs time? It seems that the hobbs would do the job just fine.

[GlennBob]

I don't know of anyone who tracks tach time.  Hobbs is pretty much universal for engine time. The only place I've seen tach time used is when an FBO is bragging that they only charge by tach time thus saving the renter a few cents.  Maybe an A & P or an I.A. can weigh in on it.

I too would be a little frustrated though.  

Glennbob

[Drew]

Hobbs time is only giving the amount of time the electrical system is on (even if you leave the electrical system "on" overnight).

From what I know, tach time does not start recording until you have oil pressure.  There should be an oil pressure switch on one of your oil lines.  Either that got disconnected or the switch went bad.

At least one of the EI tachs do not use oil pressure----it uses Engine RPM.  Anything over 1300 RPM gets measure as tach time.  If yours is this one, you may want to ask EI what is up with that---pretty much a self contained unit.

[flyingwaldo]

Hobbs time is only giving the amount of time the electrical system is on (even if you leave the electrical system "on" overnight).

This would be incorrectly installed.  The Hobbs should run off a pressure switch also.

[Drew]

hmmm...I don't have a official source at my fingertips.  However, based upon a quick check on the internet yielded pretty much the same as the below link.

http://en.wikipedia.org/wiki/Hobbs_Meter

So I challange your statement of an incorrect installation.  Please post what the FAR says (while wiki is interesting---it is not official).