How do i replace a heater core in a 1994 vw passat

I do not know exactly how the on and off switch turn work but check the cable connection from, to it main switch last. clog heater core. bad thermostat. tuff job. check hoses and make sure no air or space inside the hoses instead of coolant..

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

Sounds like the heater core and it will cost anywhere from 200.00 to 400.00 unless you can replace it your self.

Probably not. It really depends on the situation and what is going on. If you are not getting any heat it could be the heater core or it could be as simple as a thermostat.

Inspect/Replace If it is necessary to remove the heater assembly, the cooling system must be drained before removing the heater core.
When a heater core leaks, a new heater core is installed or the old one repaired.
Heater Housing

• The heater housing is usually under the dash and must be removed to gain access to the heater core.
• Procedures for replacing the heater core vary with the year, make, and model of car. It threfore necessary to consult the manufacturer's repair manuals for the proper procedure for replacement.

The heater housing is disassembled to get to the heater core. Heater Core

• Remove the access panels(s) or the split heater/air conditioning case to gain acess to the heater core.
• Remove the heater coolant hoses.
• Remove the cable and/or vacuum control lines (if equipped).
• Remove the heater core securing brackets and/or clamps.
• Lift the core from the case. Do not use force. Take care not to damage the fins of the heater core when removing.
• To reinstall the heater core, reverse the removal steps.

When the heater core leaks and must be repaired or replaced, it is a very difficult and time-consuming job primarily because of the core's location deep within the firewall of the car. For this reason always leak test a replacement heater core before installation.

yes, most likely the heater core. Need to replace, for now, keep your heater off :)

well you'll need to spend about $20 to buy the book from autozone or just go to their website the have comprehensive repair info can be a real life saver use the print option if you want and you can take a copy to your car

The heater in your car depends upon a flow of hot coolant going through the heater core in order to get hot air into the car. If the heater core is partially plugged, it will restrict the flow. If you have a head gasket that is putting exhaust into the cooling system, it will eventually get into the heater core. When this happens there is no coolant in the heater core to make the air warm. If the water pump vanes have corroded away the result will be very poor coolant circulation causing the heater to not blow hot air. If your car is equipped with a heater control valve that is not functioning properly, the coolant flow will be restricted. One or a combination of these factors is likely the culprit in your case.

To attempt to clean the core, you must flush the system multiple times. If it is still problematic, changing it is your only remaining option besides the water pump itself.

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..