Does anyone know how much it costs to get the heater and horn fixed in a 2003 Mitsubishi Lancer ES?

This all depends on the shops around where you live. Call around to a few of them and see. They may need to take a look to see exactly what is going on. Just because your horn doesn't work that doesn't mean that the horn needs to be replaced. Somethings are fixable without parts.

If the heater does not work check the relay (electrical device in the engine bay) which might have got damp or not pushed in properly.

For the horn check the fuses on the in the engine bay.

I reckon 9 out of 10 times this is where your problem is.

Apart from that the car is too new for these problems to occur especilly a Japanese car.

Get someone to checkthis out for you or you could do it yourself.

Former Toyota mechanic

the other answer is incorrect. the fuel doesn't keep pumping when you turn over a fuel injected car, it has an electric fuel pump that pressurizes the system in a few seconds when the key is turned then shuts off till the car is started. that being said i doubt it's flooded. first try a can of starting fluid and give it a shot in the air cleaner and see if it fires. if not you have an ignition problem. the module may have quit. if it does fire off the starting fluid but stalls it's a fuel problem, could be fuel pump or water in the fuel.

why don't you try this, take it to a shop and let them diagnose whats wrong with it,and see what they say the cost will be to repair it this is a lot cheaper than just taking it somewhere and say fix it,they may over charge you for something that you really don't need on it,if you get a good diagnoses on it then you,ll know what it will take to repair it and wont get taken advantage of,good luck and have a good new years.