Jump to content

Do I Switch Live Or Neutral

Recommended Posts

Help! anyone


I have a Zero kit car that I am finalling getting round to sort out the wiring. The engine and switches are from a 1988 Sierra. I have wired it up the best i can switching the live side of the sytem which the supplied loam suggested.


I keep reading on the forum about ground switching.


I have problems with my circuit and i am wondering if i have used the correct method. The RHS column switch has a number of the contacts linking to one of the fixing screws in certain switching modes which puzzled me. I connected this direct to earth and was blowing fuses so this was soon removed.


I am lost at the moment do I carry on with switched live or do I need to start again using switched neutral.


The trouble is most things work apart from the wipers are on all the time when I connect the dip and main beam to the link switch 53a


Also was does Contact "W" do on the RH wiper / lights switch as it appears not to contact to any other contact in any switching mode


Is there any one out there to help a lost sole

Electrical drawings Model (1).pdf

Link to post
Share on other sites
  • 2 weeks later...

That's not entirely correct.


You certainly would NOT switch neutral in a domestic / commercial electrical installation as this would leave the possibility of the equipment still being live when you remove the covers from it. Very dangerous.


In auto electrics, designers have become sloppy about where the switch should go "Ach, it's only 12 volts, what harm can THAT do?"


So there is the possibility of the battery going through your device and the terminal on the other end having he switch to ground. If you happen to short the terminal by another (short) way, the device would stay "on" - or if it was faulty, blow the fuse up circuit.


The main reason WHY there are a lot of switched earth's is because the body of the car is nearby and you don't need as much wire that way.


E.g - Battery -> switch -> device -> ground may mean two wires in the loom to the switch whereas


Battery -> device -> switch -> ground is only one wire to the switch and a short link to ground.


I don't think there's the equivalent 17th Edition wiring regs for auto electrics. :)


Now with the modern cars, even one wire is doing many jobs with the CAN bus systems and computer multiplexed systems.

(Which is why the guy with the lamp-onna-wire is having problems :) )



Link to post
Share on other sites

Im no auto-electric expert....but when I did the wiring in my car (home made loom), I felt it was less risky having 2 earth wires going to a switch that 2 live wires (even though the lives would be fused).


Plus like simon-says (get it?), having the body to earth onto equals less wires around the car.

Link to post
Share on other sites

ah yes i did assume we were talking about auto electrics, and it depends in which country the car was wired whether its likely to be live switched or earth switched....its not uncommon to see both styles of wiring on any single car. the horn is commonly earth switched when all the other circuits could be live switched. but on a kit car where your likely to over engineer everything including the wire ratings earth switching is just fine. i prefer live switching where practical but some circuits on my car are earth switched for convenience.

Link to post
Share on other sites

on the sierra the hand brake and brake fluid level are earth switched , could be that other items are also earth switched, but i always go for fuse -switch -device-earth


Link to post
Share on other sites

And seeing that electron flow is opposite to conventional flow it don't matter a great deal,the most important item is a fuse of correct rating, as near as possible to the battery; non chassis side of coarse.

Link to post
Share on other sites

all very intersting, and I would agree that some circuits are best wired earth switch for the reasons given.


However the main query that comes up on this forum is the switching of the stalks, which was the topic of the first post.


There are nine versions of the ford switch, some had the headlights earth switched some live. In a kit you can do it either way, and it make no difference to wire length, operation or saftey but can add a small complication to the switching of the fog light if earth is used.


Again there have been well meaning posts to rectify this, relays, diodes and the like but it just isn't a problem if the switch is wired to switch live.


My view is always keep it simple. but thats my opinion.

  • Like 1
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Create New...