Thermo Fan wont kick in

[old_mr2]

Hi Team

In my GF's Holden Astra, the fan wont kick in when it heats up. When at traffic lights it almost gets up into the 'red' on the temp gauge.

I have confirmed the fan works by putting 12v to it.

The fan fuses are all good...

My question is, what sends the 12v to the fan to start it? I think this is where the problem lies.

Thanks in advance

[Wiggles]

It could be the relay.
Find the relay box and see if there's another identical relay that you know works (like the headlight relay)
Swap for the thermo relay one temporarily and see if the thermo fan kick in.
If it does, grab a new relay and whack it in.

Also, if the temp starts getting up at the lights, switch the heater to hot and crank the fan to full. It should slow the temp rise a bit (and give you a nice sauna effect)

[old_mr2]

Well i found 2 relays (unmarked) and swapped them over, no change. But, im not convinced I was actually working with the right relay

[frostyadonis]

what year astra? im guessing TS 1999. worst model ever.
take out the thermostat, test it in an old mug with boiling kettle water.
if it opens then put it back in.
temp switch controls the thermo fan. take the punt and replace it..good luck

[slide86]

well, i work at a holden dealer....

if its a TR model astra, they have 2 thermo switches in the radiator end tanks that control the fans. these pack up after a while and we often replace them at work

they are a bit of a prick to replace. you can see them if you get under the car and have a look at the radiator end tank, the switches are located near the bottom of the radiator.

if its a TS model astra, they have a cooling module that is located behind the front bumper on the passenger side. this is what turns the fans off and on. these also are known to die, but you would probably have the light on the dash if it was faulty.

if you cant locate or replace the switch, it would be a good idea to take it to someone with a tech2 so they can check the cooling module out

[old_mr2]

its a 97 model, so im thinking TR.

I will try to check your suggestions tomorrow. Cheers.

[StuC]

my gf's SB barina with 1.4L motor in it. has started doing the same thing. There is power at the plug, the fan still works if i give it 12V and the fuse is fine. The relays in the fuse/relay box are marked for wiper, flasher and demister timeout i think. Are there temp senders in the shitty radiator for these (if any) control the fan cut in/out as well and if so do they stuff up like all of the others?

cheers
StuC

[slide86]

yeah they have a similar setup/ sender in the radiator.

have fun with an SB barina radiator......

[old_mr2]

Mine turned out to be a faulty thermo switch as mentioned, it has been bypassed for now and fan is running 24/7 until further notice.

[StuC]

mine is also the same problem. it is however 85 bux for a new one and around 35 for a daviues craig relay/witch/controller which is also adjustable. Im going to go this option coz 1 ) its cheaper. 2) i can make it kick in earlier as i feel the stock 100 degree C turn on point is just ridiculous and 3) when the car finally gives up the ghost i can pinch it back and use it for something down the track

[wagonist]

Mine turned out to be a faulty thermo switch as mentioned, it has been bypassed for now and fan is running 24/7 until further notice.

You could possibly rig it up so that there is a switch on the throttle, the fan kicks in when the throttle is almost closed (ie little or no airflow through the rad).
Did this once to another car years ago.