Trying to square away some issues with the Rover so I can get it inspected but I have two open issues:

(1) A couple months back my horn got stuck on while driving. It took me a bit to figure out which fuse to pull but since then I've had to leave it out as it will not turn off after the steering wheel button is depressed. I've checked the relay and a new one did not fix the issue. when I measure the voltage at the horn leads, upon pressing the horn button, the voltage goes up to ~12.5V and does not drop once the buttons are depressed. I've disconnected the harness to the steering wheel while this happens and the voltage still does not drop which isolated the problem to the harness between the steering wheel and the relay I believe. Since the horn buttons do not supply (+) to the relay but instead (-), what I'm assuming is happening is that trigger lead to the relay must be shorted out somewhere but IS NOT strong enough to cause the relay to latch but IS strong enough to prevent the relay from unlatching. Does this seem plausible and has anyone else ever had this issue?

(2) All of a sudden, when I need to back up and go from reverse to drive, the hill decent light comes on and will not turn off until I cycle the ignition (button does not deactivate it). I'm assuming this had something to do with a faulty reserve switch or something? Seems odd that these two systems would be connected in anyway? Has anyone ever had this issue.

Any and all help would be appreciate. I miss driving her as often as I use to and need to get it legal again so I can finally justify throwing some accessories on her. Thanks in advance.

 

It sounds like your horn issue is different than mine, but I had a horn button **** a little off and stick in the steering wheel.

 

The only thing I can offer you is to pull the relay and jump from Pin 30 to Pin 87 in the socket. This will energize the horn circuit and give you 12v to the horn. If you pull the jumper back out and power goes at away at the horn connector, this would verify that your problem is not in the wiring between the relay output and the horn. Not very likely that your problem lies in there anyway, but you would at least be able to rule that out. You can also test your switches with a multimeter to verify that they're working correctly, although it sounds like you may have already eliminated the potential for a faulty switch causing the problem.

 

One idea... re:HDC Lamp.The Interior fuse box (under drivers steering wheel) has an HDC control relay, confusingly also known as the 'brake control relay', which is soldered to the board and unfortunately non-replaceable. If this fusebox fails which normally happens from water ingress, it will cause your HDC light to illuminate intermittently. I spent months chasing this intermittent HDC light on my 2000 D2 when I purchased it. Mine would often go away on restart, notably. Swapped fusebox with a good one, problem fixed.

In other words, it might not be you going from Reverse to Drive, it might be your brake relay because your foot likely is on the brake pedal when shifting?

Not sure about horn. I think they are powered from the engine compartment fuse box solely based on looking at wiring diagrams just now.

 

Those horn buttons suck on my 03 one was loose didn’t clip in right it’s a springs in there look inside the button and see if the connection is stuck and therefore activating the horn

 

Vehicle horns The contacts of the horn relay, in the engine compartment fusebox, are connected to the LH and RH horns by PG wires. The LH horn is earthed by a B wire connected to earth point C0564. The RH horn is earthed by a B wire connected to earth header C0018. Where the vehicle horns are used by the anti-theft alarm system, the horn relay coil is connected to the BCU, via header C0286, by a PO wire. To operate the horns the BCU earths the PO wire, which energises the relay and connects the feed from fuse 16 in the engine compartment fusebox to the horns.