Clicking relay noise

[K2Surf]

For the last few days I had a really annoying noise coming from under the dash at about the height of my right knee. It's been driving me nuts.
Finally tracked it down to a relay that’s accessible just behind the very bottom of the dash, below the fuse section.
I've removed the relay, it has the following markings:

Relay
TOYOTA
90987-02012
156700-0870
12v
Denso

Any idea what it's for? So far I've checked and all work:

All lights
windows*
electric aerial
rear window
sunroof
AC
4x4 drive
horn
stereo
fan
windscreen wipers (F&R)

I've not checked (as they are not currently working anyway):
heated rear window (never worked since I bought the truck)
*Drivers electric window (hasn't worked for a while, think the motor needs replacing)

Not sure what it does!!

[BUSHWHACKER]

What colour are the wires going to the relay?

Does it just click all the time or when you are driving/ignition on?

[K2Surf]

Will let you know on the colours, it clicked every time i went over a bump, like there is a loose connection somewhere...

[NiftyNev]

Spare wheel carrier relay which explains why you get the clicking when you hit a bump.

Nev

[K2Surf]

Spare wheel carrier relay which explains why you get the clicking when you hit a bump.

Nev

Makes a lot of sense that. What does it actually do, is it just for a warning light or something?

[NiftyNev]

What does it actually do, is it just for a warning light or something?

Don't know but I would think it has something to do with the warning light that you would get if the carrier was not closed properly.

Nev