A Shorts 360 returned to the departure airport when the landing gear failed to retract. Ultimately determine maintenance had failed to return the Emergency Landing Gear T handle to the correct position following maintenance the day before the incident.

Narrative

After takeoff; I called for 'positive rate; brakes; gear up'. On the Climb check list we noticed the gear had failed to come up. I cycled the gear and it did not come up. After I called for the abnormal checklist we asked tower to come back around and land. When we shut down the engines we were able to talk to mechanic. I told him the gear failed to come up; and that I noticed the emergency landing gear accumulator was indicating lower then usually. The mechanic seemed so positive that it was the accumulator; he said it could be MELed. At first I didn't think that was the correct diagnosis for the gear not retracting; but the mechanic proceeded to show me the MEL for the accumulator so I began to doubt myself and thought he had to be correct. He then informed us to continue the flight; but to do it with gear down and to make sure we are below VLE. After completing our flight we later found out that our plane was in maintenance the day before; where they worked on it and forgot to reset the three way selector valve. We later checked the three way selector valve window; it was very difficult to look into but after looking and looking I could finally see that it was in the open position. I then went in the plane and noticed the emergency landing gear 'T' handle was pulled. I must have missed this on the preflight check; but it was at night. When pulled the 'T' Handle doesn't come down much further then when in the up position.