2007 Toyota Yaris, a/c and fan not working. also, water is leaking under the dash which makes me think the heater core is bad also. The fan was making noise prior to its failure.

If there's no external obvious leaks and not overheating, you have an internal leak, either from a bad head gasket, cracked engine block or head. Check under dash to make the heater core is not leaking onto the carpet.

Check the coolant level.

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If the Water smells like Antifreeeze then it is your HEATER CORE

If the water smells like Water or Dirty Water, then you have a LEAK.

Here is a TRICK..

Get an Aresol Can of WINDOW CLEANER.... Spray completely around your Windshield on OUTSIDE EDGES... YOU WANT IT FOAMY.

Get an AIR HOSE and BLOW the Windshield from the INSIDE and see where the leak is coming from.....

It has ALWAYS worked for me

The only fluids under the dash are coolant that circulates through the heater core, or if you have a manual transmission a failed clutch master cylinder can leak brake fluid under the dash right where clutch pedal is located. If the heater core is leaking, it usually shows up on the passenger side. If it is just plain water, you need to check how rain water could be getting in past the firewall and under the dash.

Bad heater core leaking fluid. You can either replace the heater core or you can just connect the hoses on the fire wall that go to the heater core until you are able to get it fixed to keep water from leaking into the vehicle

SOUND LIKE HEAT CORES LEAKING ANTIFREEZE INSIDE DASH.

heater core might be blown-off. also see your fuses for heater under your dash fuse panel or at the under hood sometimes where they are.check your cold lever position might be at full cold counter clock wise, move it to hot position clock wise.

yes a bad water pump will cause it not to circulate the coolant through the heater core,find your coolant leak 1st is it leaking into the cab on the passenger side of your truck? thats another sign of a bad heater core also.make sure that you don't have an air pocket in your cooling system.it has to be full for the heat to work properly.thank you for choosing fixya.com

http://www.toyotaownersclub.com/forums/lofiversion/index.php/t71011.html

There is a valve on one of the heater hoses that allows heated water to flow through the heater core when you select heat. With heat selected and car warmed up check to see if both of the hoses feel warm. If not then water is not flowing through heater core and valve may need replaced or heater core is stopped up.