mk5 golf 1.9tdi doesnt always blow hot air

[Neiltdi]

Hi Guys

My 1.9 tdi golf will take a while to get (warm) and it doesnt really get (hot) and it doesnt blow warm air continually it will start to blow cold after a while then it will blow warm.

any help/advice would be great

thanks
Neil

[skard]

Could be a failing heater blower resistor

[GrayMK5GTI]

Diesel engines are more efficient than petrol and therefore don't produce as much heat. In the temperatures we have been having recently, if you put your heater on full it will take ALL the heat off the engine (bare in mind it doesn't produce a lot of heat anyway), combined with the cold air constantly cooling the engine. Basically means that unless you give the engine some load to get it warm you will struggle to get warm air out of the vents.

The warm air you do get will take the heat off the engine so you sill start getting cold air then.

[doylebros]

I agree with the above post.

That's why the mkv have the option of aux heater.
The mk4 diesel needed a 10 plus minutes drive to get close to operating temperature.
Before you take anything apart try a 20 minute run down the motorway and reassess from there.

[Neiltdi]

Thanks for the comments.
i was on the motorway on my way home from work I'm pretty sure it should constantly blow warm air at 80mph for 15minutes after a 10 mile journey getting to the motorway averaging 50mph

[doylebros]

Has your car got Air con or not?
My next steps would be:-
Check coolant level in the expansion bottle when cold! - if ok.
Scan for faults and check measuring blocks for temperature readings.
If no access to VCDS
New thermostat
Temperature sensor -Check out this video on YouTube:

After that it's getting more difficult in terms of competency and tooling as your moving into heater matrix replacement and coolant system flushing!

The above assumes the interior blower fan is working?