You need this IMG link below - URL takes you into photobucket, but doesn’t show online. I take it the blue connector nearer the dash is the loom one, and the larger one with spade connectors is the back of the switch? Question - is the switch an illuminated one? If so, you need a positive and negative connection to the switch to make it work. Check if you can (multi-meter or 12V test lamp) on the loom connector to if see if these are on the loom connector. Best way, put one lead on the chassis - make sure it’s definitely a body connection, and find the positive on the loom connector. when that’s established, leave that lead in place, and use the chassis lead to find the negative on that connector.(take it off the chassis and use it as a finder) Sorry - I don’t have a Mk1 wiring diagram to refer to, but this is what I’d do. Now - on the switch, at a guess, the middle pins are the normal postive and negative live connection for an illuminated switch, and the offset pins are the outgoing connection when the switch is on. So, having identified which wires are live and negative, cut them off at the loom connector (one at a time) and crimp a female blade connector on it - if you have the right tools to do this. Halfords sell crimp connectors in small packs, so make sure you get the right size for the switch pins. You can solder these on, but be careful, as solder can run down onto the blade and interfere with a connection. Do the positive first, then the negative, pushing each one onto the switch contact singly, that avoids any shorts, flashes and bangs! The remaining wire is (it says here) the switch wire to the HRS, have you fitted a relay or not? If a relay, then the last wire needs to go on the offset negative connection on the switch,.as the relay is positive fed to the coil and needs a negative to work. If no relay, but a direct connection to the heater, then connect that lead to the positive side of the switch, on the offset pin.
Normally the light is connected internally across the offset pins, so when the switch is on, the light works.You can check this before adding the third wire, if it lights- we are both right. If it doesn’t then I’m wrong! You can call me anything you wish, but there may be a remedy, which I’ll pass on if it doesn’t work. If the light works, than connect the third wire as mentioned. Crimp pliers are expensive, £15 odd. but don’t buy one unless you need it in the future. Odd times when I forgot my crimp pliers I have used ordinary pliers (good ones) and used the cutting edge to mske the crimp, but make sure you don’t chop right through, or you have a broken connector. You can also try squashing the crimp part with the gripping nose of the pliers, but it takes a good pair (six inch pliers or better) to make a firm connection. Give it a pull when done, if it comes off, the crimp isn’t good enough. Disconnecting the battery would be the safe procedure, but then you won’t be able to check pos and neg leads. However, if you make a note of which wire is which (white electrical tape helps, if you have a permanent marker) and then disconnect the battery then you can proceed without doing any damage. Last thought - you need to strip the insulation off the ends of the existing wires to make a good connection with crimps, strip around 5-6mm and be careful you don’t cut through some of the outside strands when you do this, Crimp pliers have a stripper part, but again, not much use if you never use them again. Also twist the strands, or you may have the odd strand sticking out and causing problems.
PM me if you are in doubt.
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