Discovery 1 cruise control not working

Hello all, first post on this forum so here goes - and thanks in advance for any replies.

Cruise control not working. It's a very late model 300tdi ES auto. Seem to remember it worked when I bought the car about 10 years ago but never really bothered with it - would like to get it going, it's the latest thing on a long list I've been working through!

So far I've replaced all the vacuum hoses - including the one to the brake pedal. Taken the pump out, direct wired to a 12v battery and system vacuums up ok - can see the bellows contracting, pump works ok etc. I've now replaced the pedal switch with a new one, still no joy. There didn't seem to be anything wrong with the old one (on a visual inspection) but it was the cheapest part to replace. I've checked all the brake lights, they work ok - I'm not sure if that would make a difference but checked anyway. ABS light comes on with ignition, goes off when moving etc all as it's supposed to. CC switch lights up when button pushed so power to there. It just doesn't do anything when I try to set it with the steering column switches. Noted that speed needs to be above 28mph so made sure I was going over that when testing.

So, where do I go from here? I'm not an electrician but I tend to think it might be an electrical fault. Is there an easy way to check this (don't have a multimeter).

Over the years the only things I've changed have been installing a tow bar (LR specialist fitted) and I did have the brake light switch replaced - not the CC one - when I realised I had no brake lights! (dealer fitted at same time as MOT). Not sure either of these would be a cause but I'm noting it to give the full story.

Any ideas gratefully received! Have been looking through loads of posts on various forums about this, most seem to suggest hoses or brake light switch - but that doesn't really help me i'm afraid.

Search and u shall find: https://www.landyzone.co.uk/land-rover/disco-1-cruise-control-repair.231884/
This link gives u the information on testing the individual items that makeup the cruise control system for the D1.
Your going to need a voltmeter at least to carry out some of the tests.

All issues that are possible possible with the D1s has been asked before.

Thanks for this link. Working through the checklist, everything is ok down to the Vacuum pump test - that's where I'm coming to a full stop. Nothing happens when connecting with the wires as detailed. What's the next logical step before taking out the CC module to check it? I'm guessing there's a wiring fault somewhere, but not sure how I go about finding it! Bearing in mind that the pump worked, as did the bellows, when I connected the pump direct to a separate 12v battery.

OK, so what stage did u reach in the fault finding list shown in the above link?

So far, I've done:
Replace all vacuum hoses
Replace brake pedal cc switch
Test vacuum by connecting pump to separate 12v supply - after disconnecting 3 pin socket just in case - all seems ok, pump works, bellows contract and no leaks
Road test - light on switch ok but no cc with set/accel button
Electrical tests as per link = ground test ok; main voltage test ok; secondary voltage test ok; brake pedal test ok; steering wheel set/accel test ok; steering wheel reset/decel test = ok; vacuum pump test = nothing happens, double checked = still nothing so that's where I've got to and i guess where the problem is, but not sure what to do next.

Could be as simples as an iffy electrical connection at the pump which I had a few years ago, so clean and then a dab of Vaseline before pushing the protective shroud back on, no issues since then.

There's two other options, the vacuum pipe is on the wrong connection at the pump, one sucks (black) the other blows (white) if I remember correctly, and then there's the 12v supply isn't reaching the pump.

Ok, cleaned the contacts on the pump (although they didn't look dirty), reconnected. Checked no loose wires on the 3 spade connectors, all seems ok. Checked vacuum hose on the correct spigot - it is; test drive = still not working so that leaves a bad connection/broken wire somewhere between the pump and the control unit behind the glove box. Looking at how the plug from the pump disappears into the wiring loom, then into the bowels of the car somewhere, I'm starting to feel that this might be a bit more tricky to pin down!

Ok it's now getting somewhat difficult, but a check of the ECU circuit board as stated in the link, it may reveal that some resoldering may be required.
As for the wiring to the pump, the Haynes manual shows the termination points of the pump wires.

I'm thinking that it might be the point at which I let the local Landy specialist have a look at it...