VN/G S1 thermo fan working intermittently

[ST1LO]

Hey all, I'm needing some help.
I recently bought a VG ute (same as VN S1), its been sitting a fair while and the thermo fan was jammed up so i replaced it with a VS one and made a mini loom to bridge the 2 powers and 2 earths.
Anyway its not getting power so i replaced the temp switch with a new one today and let it idle.
It got up to 3/4 and the fan came on but only stayed on for about 10 seconds and turned off again, its doing this about every 15-20 seconds.
Have swapped relays over without change, ran a wire to the fan itself and that is running fine also.
Anyone have any ideas?

 

[Bizmark]

Is the temp gauge working properly? Thats another thing you could look at.

 

[ST1LO]

yeah im pretty sure its working fine, top hose is pressurised and its hot to touch, plus it has that hot engine smell.
I bought a new thermostat today but failing that im out of ideas.

 

[LordMayhem]

the on off are what the thermo's do they pulse on and off to keep the car at a certain temp. not coming on till 3/4.......is the temp switch adjustable as in you can set what temp the thermo comes on at?

 

[ST1LO]

I dont think it is, its just a Tridon standard replacement one.

 

[groupa294]

IS it a VS one, is it single or tiwn fan??????

 

[ST1LO]

VS single fan.

 

[Brett_jjj]

Try testing the cooling fan by removing the wiring from the engine coolant temp sensor,theres 2 temp sensors,ones for the temp gauge,the others for the ECU,the ECU one is the one you want,it has multiple wires going to it,the gauge sensor only has 1 single wire.Anyway remove the wiring connector from the ECU temp sensor whilst the engine is running.About 12 seconds later the cooling fan should start up on low speed.After a further 6 seconds,the cooling fan should switch to high speed.If the cooling fan does this,its working ok.

 

[ST1LO]

Thanks Brett, ill give it a shot.

 

[Cheap6]

Try testing the cooling fan by removing the wiring from the engine coolant temp sensor,theres 2 temp sensors,ones for the temp gauge,the others for the ECU,the ECU one is the one you want,it has multiple wires going to it,the gauge sensor only has 1 single wire.Anyway remove the wiring connector from the ECU temp sensor whilst the engine is running.About 12 seconds later the cooling fan should start up on low speed.After a further 6 seconds,the cooling fan should switch to high speed.If the cooling fan does this,its working ok.

That's a good place to start, although as the windings on the VS fan are jumpered together for the VG install there will only be one fan speed, that being the "high" speed.

There is a lot of info. on cooling fan operation in the "How To" on switching VN-VP fan manually. That will help in understanding the fan operation and hence diagnosis.

Also, try checking for ECM fault codes (see the "How To" on checking fault codes), then clear the ECM memory, drive the car ~10-15 min and recheck for them again (and disconnecting the coolant temp. sensor will trigger a fault code). Some fault codes will cause the ECM to switch the cooling fan on by default.

I suspect that it is the constant switching that has killed the original fan.

Try wiggling the coolant temp. sensor wiring connector and harness and see if the fan switching behavior alters. Likewise tapping the ECM case with your fingertips and wiggling the ECM wiring harness and connector block.

The fan should also run constantly with the ECM in diagnostic mode and ignition on i.e. with the paperclip across the ALDL connector as per checking fault codes. That should tell you if the fault is in the ECM switching circuit or in the input to the ECM/ECM decision to switch circuits.