heater on temp down

[tazmania_1981]

hi guys
i have 98 passat over 150.000 miles running very good
but now one problem guys
when i put the heating on my engine temp goes down half way
i dont believe this is normal
i had a golf before and it was always in the middle no problem what i was using inside.
anybody knows why is this happening?
coudl it be fan switch falut or water temp sensor.

[Issac Hunt]

thermostat?

[tazmania_1981]

do u think thisd is happening becauyse of the thermostat

[Issac Hunt]

its possible. No guarantees though, its hard to diagnose without seeing the car.

[David_Cooper]

I have a '99 Passat, APT engine. It never went half way on the gauge and the heating was average at best. Changed my thermostat and did a thorough cooling system flush and really pleased I did.
It now gets up to 90 degrees (halfway) in a couple of miles and stays there, regardless of what sort of driving I do or use of the heater!

Very cheap part, (mine was £4.99 for a QH one from eBay) but labour may be dear depending on what engine you have!