Checking radiator cooling fan

My 2002 TF 135 started overheating while driving in stop-start city traffic yesterday, a warm 27deg here in Adelaide. This hasn't been an issue previously.
Temp gauge got to just above the ¾ mark but returned to normal range once we were in clear air and moving. Temp also went high again climbing windy hills roads but dropped quickly on more level terrain.
No coolant loss and inspection of the dip stick and filler cap shows nice clear oil, no mayo.
I'm suspecting the radiator cooling fan may not be working? Checked the fuse and all OK there. The engine bay fan ran for a while after stopping with engine off.
Is there a simple way of checking if the radiator fan is functioning correctly? Help please.
Possibly just coincidental, but a couple of weeks ago the expansion tank cap 'blew' with the associated spectacle of heaps of steam and about 1 litre of coolant loss. A new (genuine) cap appears to have solved that issue.
 

The fact that the engine bay fan runs means the temp sender is doing something useful.
Why not unplug the fan and apply power and earth directly to it? It should run, if not it's buggered, and if it does run, well you need to see if it's getting turned on by the ECU.
which would involve getting it up to temp, and seeing if there is any power getting to it.

If you unplug temperature sensor on the engine which sends info to the ECU radiator fan should start working. If not either fan is not working or engine ECU is not sending signal.

To test the fan's operation directly, on cars with the lucasfob (square) without AC.
Remove the yellow relay under the bonnet and use a suitable wire shunt to bridge these two points. With the ignition on, the fan should run!
 

Does that apply to both f & tf David? It’s such a long time since I had the tf I can’t remember now.
Information like this is useful to store in a dusty drawer of my brain, instead of relying on someone else’s dusty drawer.
Thanks.
M

It does apply to MG F and mk1 MG TF (Lucas type fob) but only in case you do not have aircon fitted. It does not apply to mk2 MG TF (Pektron fob type).

Thanks Roverlike, I was searching high & low for the yellow relay.........mine has AC!

All Oz spec cars have AC, which is why I made the suggestions I did.

Roverlike wrote:

It does apply to MG F and mk1 MG TF (Lucas type fob) but only in case you do not have aircon fitted. It does not apply to mk2 MG TF (Pektron fob type).

David Aiketgate replied:-
Thanks Damir,
I will amend my post to reflect that...
David

 

OK. Thanks for the guidance, process of elimination indicates the ECM isn't activating the fan which otherwise does run.
I think I heard somewhere that there are exchange services offered by some firms - is this correct and if so, where to go? Anywhere here in Oz (Cobber?)
It's a Mk1 TF with square fob, Lucas.

Not in Oz that I'm aware of.
I wouldn't think it too difficult for an electronics geek to fix.
On my Triumph TR7 it had a little box of tricks made by Pektron, what it did was control the pop up headlights with a delay timer so the lights would momentarily stay up so as the lights could be flashed. It had shat itself so I got a geek mate to crack it open and he replaced all the crap soldered to the circuit board but the chip.....Sorted!
I ended up not using it anyway as I ended up discreetly fitting the car with both fog and driving lights, under the front bumper, it made more sense to use the driving lights for flashing purposes (saves the pop up mechanism for unnecessary ware and tear)

 

If in doubt you could always create your own fan control circuit using one of theses and a simple relay. in line temp switch