Thanks for this diagram, I'm unsure why my copy of RAVE doesn't seem to have it.
According to the diagram, relay #3 ("heated front screen relay) is what makes the clicking sound. The timer relay #9, which is the replacement part that I have (the grey unit PRC 6796) appears to be positioned behind and to the right of the heated front screen relay. I'll take another look. Things are packed in pretty tightly behind the steering column so I may need to remove some neighboring relays to access the timer.
I had another look under the steering column for the heated windscreen timer - the gray one, see photo in post #9 above. I can't find it anywhere. There are blue, black, yellow, and gray relays (labeled for other functions), but after 20 minutes of searching with a flashlight and groping where I couldn't see, I'm still not finding it. Does the timer live somewhere else? I also can't find the relevant diagram in my copy of RAVE. I'm leaving the kick panel off for now in case someone can give me precise directions, in which case I'll go back out and have a look for it again.
There is a space for the heated windscreen timer in a gap behind the black relay, but there is no female end for it to plug into. There is clearly a second row of other relays closer to the firewall, but nowhere I can find that would receive the gray timer that I have.
Okay, here is a guess at a partial solution. Both photos of relay area next to steering column. First photo shows wiring coming out of the harness and terminates in a 30A fuse. Second photo shows the bank of relays. I removed the front row from their tabs to show the back row (closest to the firewall). It's obvious where the heated front screen timer should go: right between the two yellow ones. But there is nothing there for it to plug into. So perhaps a previous owner pulled out the timer (and the receiving end) and connected the wiring to the fuse as some halfass workaround to an issue with the screen. Any other theories given the evidence?
More follow-up: found the timer in the passenger side footwell, thanks for that suggestion. Replacement timer made no difference, original problem persists with the heated front screen not switching on. Next theory: the large crack running through the glass.
Have you checked if there is power getting to the windscreen?
Also, I think there is a wire connected to the oil pressure sensor which tells the relay that the engine is running. Maybe bad or disconnected ? You are testing with engine running?
Copy on testing with engine running. Previous owner installed an aftermarket oil pressure gauge on the dash so I'll have to look into the pressure sensor switch. That's a good suggestion. Is there a connection for that down by the oil filter?
I just spent half an hour scrolling though RAVE and couldn't find the location of the sensor. As an aside, I'm curious to know if there is a different version of the file than the one I have. I downloaded copies from roverresources and from rangerovers.net - both turned out to be the same document for the 1992 model year. The PDF is an image, so I can't search the file for specific terms the way I can in the D1 workshop manual. I'd be glad to know if there is a searchable version out there.
In any case, is this the oil pressure sensor switch? Link to Atlantic British website. For $8 it seems like a no-brainer to replace the part since for all I know the truck still has the factory original.
Next challenge: finding where this thing is located. Any guidance or photos would be helpful.
I guess there are about eight different versions out there (1987 - 1994).
If anyone is interested, the manual to which I refer can be found in the link in my signature. It will take you to a google folder with lots and lots of manuals. Anyone is welcome to whatever they like.