To show up to a CFI checkride is it ok to have a first class medical which has only second or third class privileges due to being more than 12 months old? Also I understand a CFI can teach with only a third class medical correct? I would rather not have to spend the extra few bucks if all I need to teach is 3rd class privileges anyhow since I can use it for about another 4 years or so.

A third class is good enough for a CFI checkride.

A CFI doesn't need a medical at all to teach in certain cases. A 3rd class will be just fine for the checkride.

That is pretty much when you are not PIC, but on a your check ride don't try and fly without your medical because you are PIC.

Not to mention that you are also exercising commercial pilot privileges if you're being compensated. Keep it at second class standing and you're fine.

I took mine on a second class which was 15 months or so old with no problem. This was where the above sentences come from as the inspector used this as a basis for our discussion on medicals. Your FSDO experience may vary.

Third class medical privileges are the minimum medical requirement for any checkride involving flight.

To show up to a CFI checkride, you should have a very good idea of the answer to this question or at least where to find the answer in the regs.

Checkrides require a 3rd class medical (even an ATP checkride only requires a 3rd class medical). And yes, your First Class medical that is old enough to only be good for the class privileges qualifies.

Acting as a flight instructor requires at least a 3rd class medical if you must act as PIC or as a required pilot. If not, no medical at all is required.

All these rules are in FAR 61.23, entitled "Medical certificates: Requirement and duration."

... and yes, you're only required to have a 3rd class medical to instruct. 119.1(e)(1) excludes it from being a "commercial operation"

I asked an inspector once about this, and she said that they now interpret flight instruction as "educational services" not flight services.

/me shrugs

only problem with keeping a third class while instructing is if something else cool pops up along the way that requires a second class you're outta luck.

You are not exercising commercial-level privileges while instructing. It is exempt from that...you do not need any medical to instruct, as long as the student can be the PIC. You do need a third class to take the checkride, since you will be PIC.

Some 141 schools may require a 2C for their instructors.

I'm not sure how the student could be PIC. At the few flight schools with whom I've flown, the CFI is always PIC per insurance requirements. Unless the CFI is flying without compensation, how could he or she have only a third class medical?

Plus, even if somehow I missed a reg on that one, you can't get paid to ferry planes to maintenance, etc., without a second class, so you might as well keep it current.

Part 119.1(e) has to do with exemption from requiring an air carrier certificate, I believe. Correct me if I'm wrong, but that doesn't have anything to do with whether CFIs need second class medicals while instructing.