Golf V: Heater Not Working? Troubleshooting

Hello, I have a Volkswagen Golf V BRU 1.9 PD.

The problem is that the heating is now blowing cold air, and the thermostat has already been replaced.

The upper radiator hose is hot, while the lower one remains cold.

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Cooler outlet temperature, according to vcds, is 35 degrees Celsius during operation.
Idling: approximately 75 degrees.

I also disconnected the thin hose from the expansion tank, and a good amount of coolant came out. I think this allows me to rule out the water pump as the cause.

I would be grateful for any advice.

Best regards, Chris.

chriskross wrote:

The upper radiator hose is hot, while the lower one remains cold.

What are we talking about? The water cooler or the heat exchanger for the interior?

Have you ever checked the error memory of the heating/climate control system? It's possible that the servo motor for the temperature flap is defective, and the flap is stuck in the cooling position.

Hi!

The hoses connecting the water cooler to the heat exchanger are hot.

chriskross wrote:

..the hoses to the heat exchanger are hot

Then you know what's up. Either the actuator or the valve is defective.

TDI-GTI-4-Motion wrote:

chriskross wrote: ..the hoses to the heat exchanger are hot Then you know. The stepper motor or the valve is defective.

Okay, I will check that.

"But what I don't understand is, shouldn't the lower radiator hose also be hot?"

chriskross wrote:

but what I don't understand is, shouldn't the lower radiator hose also be hot?

If the thermostat is open, yes, but if it hasn't yet reached the opening temperature, it will remain cold.

Hi!

I just replaced the servo motor for the temperature flap (part number V68), but the error code is still the same as it was before.

What I observed with the servo motor is that when you set the Climatic control to cold, the motor moves to its lower limit, while when you set it to hot, it stops at the halfway point.

When I run the basic calibration, it goes from stop to stop.

The MWB 12 temperature control valve is only opening to approximately 120 degrees instead of the expected 250 degrees when it should be fully open.

Hi!

I finally found the error; it was the G191 exhaust temperature sensor that was providing a false signal of 80 degrees.

It would also be helpful if there were a German label file available for the Climatic Golf V.

Best regards, Chris.