VW Golf 2 Heater Not Working? Troubleshooting

Hello fellow enthusiasts,
bei dem Golf 2 vom Kollegen funktioniert die Heizung nicht mehr richtig. Er fährt morgens los und nach einiger Zeit wird es im Auto auch angenehm warm und die Anzeige zeigt auch den üblichen Wert an. Doch dann wird es kalt bzw. es kommt nur noch ein laues Lüftchen. Die Anzeige bleibt auf dem normalen Wert stehen. HaDo you have any ideas?

Best regards, Thomas.

Hi,

I used to have the "root" Passat, but check the control valve for the heat exchanger: This valve is operated by a Bowden cable (coming from the heater slider) and can be defective (which was the case for me before). Is the coolant level normal? Make sure it's not leaking (indicating a blown head gasket) .

haehnlein wrote:

Is the coolant level normal?

I hope it's not blowing (head gasket failure).

Those were also our initial ideas (e.g., ZKD, water pump, etc.), but the coolant level in the expansion tank remains constant.

haehnlein wrote:

Hi, Control valve for the heat exchanger: This valve is operated by a Bowden cable (starting from the heating slider) and may be defective

.

But if the valve is adjusted via a Bowden cable, it shouldn't actually get warm at the beginning. That's the point that makes me suspicious.

Hi Thomas,

Just expand it and bridge the gap with a piece of pipe plus clamps (attention, it must withstand 1.3 bar). I mean, back then, my heating system would have also been spinning when that part was defective .

Hello Christian,
Okay, so the valve is manually adjusted using a Bowden cable, which controls the amount of water flowing through the heat exchanger. Is that correct? After that, your explanation sounds good, and we will investigate the issue. - Thank you.

Thomas.

Thomas K wrote:

Right?

Hi Thomas,

Okay, I understand. Please provide the text you would like me to translate from German to English.

In the case of the TDI system, for example, the heat exchanger is continuously supplied with air and its operation is controlled solely by the ventilation ducts.

Based on your information, I believe a defect in the valve area is very likely. You should also change the coolant at the same time (it can never hurt ). Of course, it could also be a foreign object in the system that is causing blockages when the engine is warm. Have you ever put radiator sealant in it } (I hope not -> it's disgusting stuff )?

Hi Christian,

haehnlein wrote:

Have you ever put radiator sealant in (I hope not -> it's disgusting stuff )

?

I certainly hope not. But it's hard to understand the situation. My colleague bought the vehicle about a year ago at a good price, from the third or fourth owner. Of course, the coolant should be changed, as it's probably already old and might be contaminated. And it's best to flush the system as well.

Hi,

'In my opinion, the Golf 2 never had a cable-operated valve for controlling the airflow to the heat exchanger. The control of the warm air was achieved via a flap in the air box.'
The only thing that existed was this pressure-reducing kit with a bypass, which was retrofitted to many 'Golfs' back then to prevent the heat exchanger from bursting. Of course, something could also be clogged in this pressure reducer.

Best, Andy.

Hi Andy,

That sounds good -> meaning, the problem is probably there (pressure regulator). My old Passat, manufactured in 1985, definitely had that control valve with a Bowden cable (I even still have the old one here ). I didn't think the Golf II would be different .

Hello everyone,

The Golf II doesn't have a heating valve controlled by a cable. The heat exchanger is always filled with water.

'I had a problem with my Golf where the heating only blew cold air after I had been idling in traffic or stopped at a red light for a while. This was due to the bypass valve, which was allowing too much hot water to flow through. Check if the bypass hose is warm when the heating fails. As a solution, I removed the bypass valve. However, I would only recommend this if the heat exchanger is not the original one. Otherwise, you're very likely to get a free 'Turkish sauna' experience. (I even experienced it with the bypass installed).'

Regards,
Thomas.

I'd like to thank you in advance for your answers.
So, to summarize, it's likely that the valve controlling the flow to the heat exchanger/bypass is defective. There's just one more question to consider. The thermostat can probably be ruled out, as otherwise the temperature display would show fluctuating values.

Hello Thomas K,

To be absolutely clear: there is no heater control valve in the Volkswagen Golf II.

The bypass is a partial short circuit between the inlet and outlet of the heat exchanger. It is easily visible in the engine compartment, near the firewall, on the heater hoses.
The bypass was retrofitted to almost all Golf II models as part of a recall campaign (I believe only the very last models were not affected). The reason was that the heat exchangers were repeatedly bursting. The bypass was intended to relieve the pressure on the heat exchanger. However, in practice, the heat exchangers still burst (as happened in my case). So, if you already have a new heat exchanger installed, you can remove the bypass. In my experience, this improves the heating performance, especially at low engine speeds.

Regards,
Thomas.