First of all, Thanks to scottydog, a full copy of the D501 1986 Wiring diagram has arrived, and I am indebted to him for going to all that trouble, especially as he wont accept any payment for the copying, and postage, Thanks Simon, I owe you one
Now that I have had time to go through the various ccts, I have found a common link with all the items, bar one, which if it goes intermittent, will give the problems that Martin had. You may recall one of my early postings re. this problem:-
JohnC wrote:so there will be a number of earth cables coming off these relays but they all will not go directly to the earth seperately, I am sure each of the relay earths will go to a buss bar of sorts, ie:- a junction, where they will all be connected too, with one larger cable going down to M10. I think that is where the fault lies,
Well it turns out that there is a junction 495 on page 1 of the manual, which you will see has one (large) wire going to the earth point I called M10 (in my manual), which on the 1986 manual, is called 517.
If you check the ccts for the Horn relay, its coil goes to earth via 495. The Full Beam relay coil goes to earth via 495 The Computer earth goes via 495, the Wipers relay coil goes to earth via 495, and the Door Locking relays coil goes to earth via 495, as does the earth from the remote locking receiver.The cct below shows how the 495 junction is used for the main beam relay coil earth, and an earth for the Warning Lights Box.
The only one that does not pass through 495 according to the manual, is the radio, as its earth goes to the other side foot well. However the manual shows the ccts for the LHD Alp, and I can only think that for some reason or another, the Radio earth for the RHD Alp could be different, and go to 517 via 495, but thats only a guess.
The manual writers have conveniently done a diag showing Earth 517, and junction 495.
I dont know, but I suspect 495 is an inline crimp connector, or similar, with a large wire coming up from 517 into one end, and a number of smaller wires from the other end going to the relays, or the other non relayed components.
Junction 495 could be buried in the wrappings of the loom, but you should be able to get to it. I suspect you can feel a lump in the loom.
My feeling is that there is an intermittent wire in that junction, and when you dropped the fuse box down the twisting of the loom remade it. I really think this junction must be checked.
Hope this helps when you have time to get around to it
John
1990 GTA Atmo, 2003 Jaguar X type 2.5SE Auto, 2018 Kia Picanto GT-Line-S 1.25