2004 VW passat not heating

check it the heater control is allowing hot water through the heater core.(turning the tap on )

Could try to change temperature sensor (due to MIL light), but it doesn't cause no heat in vehicle. Most likely caused by air-lock in heater hoses at heater core. Try bleeding hoses to eliminate air.

There are a few things that may have gone bad that can stop your heat from working.Heater core, blend door, etc. You will have to have this problem diagnosed by someone who knows what parts to check.

i think u have air traped in heater core ,seat in car and push gas pedal up too 3000 RPM and hold it for1-2 minutes turn heat on and should come on good luck

This happened to my Passat, and little by little the air kept getting colder and colder until there was no heat left....I just took it in to get looked at- The heating core is gone- the part itself not that expensive, but since they need to take apart the entire dash to replace, the total job is like $800, $700 of that is labor!

did you tested climate control switch for power

There is an electrical relay that is malfuctioning. I had the same problem on my 2000 VW Passat. I just got it fixed, part cost 48 dollars and labor will be about an hour.

Try removing he heater hoses going into the firewall(when cooled)and blow the heater core out with compressed air.Or you could have the cooling system flushed.

There are known problems with this vehicle's heater core not getting enough coolant flowing through it to blow hot air.
1) Even if the coolant looks good, there are problems with the heater core plugging up. One solution is to use a heavy duty cleaner (CLR pipe cleaner) to back flush the heater core. To know if the heater core is plugged up, disconnect the 2 heater hoses at the heater core and somehow connect a hose to one end of the core. Try to flow water through, it doesn't have to be high pressure, and there should be a steady stream. If not, try to get the cleaner directly into the heater core and let it soak. Then back flush it and a lot of scale should be seen coming out.

2) The other problem is that since the heater core is the highest point in the cooling system air tends to get trapped in it. This should only happen if the coolant goes low or someone has opened the system to service it. There are a number of ways to bleed the system (vacuum bleed, pressure bleed). One of the hoses should have a small hole in it for bleeding air, pull that hose back just enough so the hole allows coolant to flow out of it. Then accelerate the engine and get a good flow coming out, when no more air bubbles are present, there should be good heat.

3)I've heard of bad water pumps with low flow causing issues as well as an aux. water pump not fuctioning correctly leading to poor heat output from the heater core. Someone should confirm this as I cannot get much information on the aux water pump(electronic pump by the alternator that is supposed to run after the car is shut off).

Hope this helps.

Ok, have your coolind system backflushed. Your heater core could be clogged. This could have been caused in using the wrong antifreeze system or mixing the green with the vw g-12 antifreeze. This could ran you about $110 to 150 dollars at a radiator shop...stay away from the Jidffy lube or oil doctor's . This could be your cheaper alternative to solution to your problem..good luck..