why does my water temperature go down when i switch my heater on?

[fozziie]

my cars never been up above 90 degree's according to the dial. I used to have a MK3 Astra with a dodgy thermostat, had to keep using the heater trick with the windows down, that said, i only had the astra 2 days before i picked a fight with a mitsi warrior and came off significantly worse!

[javalin]

>water pump slowing down
water pump is driven by the aux belts on some and cam belts on others - so won't slow down.

Ah it must be winter - thermostat issues starting already!

+10 thermostat issue - stuck open or shut.

J

[Khare]

>water pump slowing down
water pump is driven by the aux belts on some and cam belts on others - so won't slow down.

Ah it must be winter - thermostat issues starting already!

+10 thermostat issue - stuck open or shut.

J

It'll be stuck open mate  If it was shut the engine would roast like a Christmas turkey. Also water pump can slow down due to the wear on the fins that push the water.

[sharki786]

waterpump was replaced in january.

[Len]

Never seen this in my car so as said its the thermostat.

[harlemex]

Khare is spot on with his info. 100 percent.

[A7 UFO]

I used to have a MK3 Astra with a dodgy thermostat, had to keep using the heater trick with the windows down

I did exactly the same with an astra that I used to commute in