Timer Placement

I want to install my timer in my garage. It is not heated and will freeze in the winter. Should I install an outdoor timer or will an indoor also work.

 

The timer is an electronic device and is not subject to freezing problems. I'm not sure, but it could be affected by moisture. I would locate it as close to the manifold where the valves are as is possible/practical. Cut down on the wire runs as much as possible, and keep it as simple as possible. This might not work for you, but mine is on my basement wall and the manifold is on the outside of the same wall directly opposite. The wire lengths are less than 4' each and nothing is buried. I must be OK, it's been working fine for 25 years.

 

Indoor Timer vs. Outdoor Timer

In all the timers we sell http://www.sprinkler.com/buy/controllers

Outdoor: Transformer is built into the timer and needs to be wired with a pigtail.
A door is provided to protect against the elements
Indoor: Transformer is on the outside and plugs directly into an outlet.
Usually does not have a door.

 

I'm still suprised when I see new installs with the valve manifold buried (down here at least), even my neighbor buried his after I suggested he match what I have. He had to mess with a couple of his solenoid valves and finally understood why I suggested what I did.