Passat TDi Heater problems - Dizco
My 1998 Passat 1.9TDi diesel has a heater problem. Engine is warming up normally, but with the climate contol set to High the fan blows cold.

The only time I can get heat from the system is when travelling on the motorway, 70mph plus or with revs 2400rpm plus when it functions normally. As soon as you slow down/revs drop, the heater then blows cold again.

Local independant garage have checked that the head gasket,thermostat and cooling system are all ok. They've also tried blasting the system through with compressed air, but still the problem remains.

Has anyone please got any other suggestions before winter really sets in? Thanks.
Passat TDi Heater problems - DysonC
Sounds like the heater valve is not opening fully.
Passat TDi Heater problems - elekie&a/c doctor
Possible heater matrix is blocked.This car may have Valeo french heater unit which suffer with blockages similar to Peugeot/Citroen models.There is no heater valve on this model Passat.
Passat TDi Heater problems - Aprilia
Feel hoses to heater matrix. If inlet is warm and outlet is cold then you have a restriction somewhere in the heater circuit. Could be clogged matrix or collapsed hose etc.
Passat TDi Heater problems - DL
Could be a 'complex' climate control air blend servo motor problem?

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