how can i fix my heater/air con on my peugeot 306?

Just a word of warning. The little motor runs on pulses, it does not run beyond certain points, i.e. it is just as important to relocate the exact tooth positions as it is to relocate the timing gears/belt elsewhere. Otherwise straining will possibly do damage at full open/fully closed flap positions.
BUT.. you will be unable to enjoy driving , or get a fair sale price unless you fix it somehow. All the air in the car comes by this flap.

oldjohn
September 2015

The temperature is controlled by a flap. The flap has an axle and moulded gearwheel. This protrudes from the airbox housing . The position is (UK) about the level of driver`s left knee, remove the console side facia panel to get a look at it. By this I mean use a hand mirror or, better, poke your phone cam and take several shots. Expect to see a little motor which has a gear meshed with the flap gear.
If the motor gear has lost a tooth, buy a replacement. If the flap gear is broken, like mine , this is very bad. I took out the motor and made a manual control to hold the flap in mid positions. Back to the good old days. How I did it... First, drill a 2mm hole where you think a shaft should be in the fascia. Then poke wire and measure and adjust to get final hole straight in to the flap axle cog.
I suggest jamming a tube on to the cog, making this the shaft with manual control lever at your left knee. You need friction or mid-range detents.
The flap is quite heavy, the gears work continuously , the black plastic gets brittle in the heat. A jerk will snap a tooth if unlucky.
ALTERNATIVELY remove motor and remount it end to end. Action will be reversed. Use JB WELD, bits of plastic etc. It is a 5 wire servo, maybe reversing some connections will " restore " action..... and Best of Luck.

oldjohn
September 2015