Page 1 of 5 123 ... LastLast
Results 1 to 10 of 48
  1. #1
    Join Date
    Mar 2007
    Location
    Maldon Essex
    Posts
    581

    Electrical stuff

    I am going to run 2 cooling fans, I want these to be switched in 3 ways. I have 2 different range temperature switches mounted in the radiator and I want these to switch one fan each, not a problem with a couple of relays. These 2 will also be permanently live so that they can keep running with the ignition off if they need to. However I also want to have a switch on the dash to turn both fans on at the same time so that if I arrive in traffic in hot weather I can pre-empt the inevitable temperature rise however this will only be live when the ignition is on, not a problem. But, I have a single pole switch for the dash and at the moment I can't get my head round a way to wire this without creating a bridge allowing any one of the temperature fans to switch both fans on on at once. I can resolve this if I use a double pole switch but I have partly wired the back of the dash. Anyone got a solution?

  2. #2
    Join Date
    Aug 2014
    Location
    Leicester
    Posts
    264
    Use the switch to drive a relay with enough normally open poles. This would also help with the current that you are likely to need to start the fans.
    Lee
    Chairman UKCC

    DAX De Dion, 400 BHP 6.0 LS2, French Racing Blue
    GD427 mk3, 325BHP 5.0 RV8, Blue - SOLD

  3. #3
    Join Date
    Sep 2004
    Location
    Broughshane Ballymena Northern Ireland
    Age
    70
    Posts
    531
    James ,

    You need to use another relay to override the fan relays . This relay will be operated by the single pole switch using an ignition supply to power it and the output of it wired to switch an earth to energise both existing fan relays .

    Jim

  4. #4
    Join Date
    Jun 2014
    Location
    Swansea
    Age
    58
    Posts
    192
    Hi James

    You could put a relay (normally closed) in between the dash switch and the connection to the fans. This relay can be operated by either of the thermostat connections to the two fans so when one of the thermostats switches the power to the fan it also supplies power to the relay which opens the relay thus cutting the power to both fans from the dash. In this way the temperature fans can only operate one fan.
    Please see attached a rough diagram.

    Hope this helps.

    Rob
    Attached Images Attached Images
    Rob

    AK Gen I - 4.6l Rover V8, Stage III heads, MC1 cam
    On the road March 2019

  5. #5
    Join Date
    Mar 2007
    Location
    Maldon Essex
    Posts
    581
    Fantastic guys, Not expecting such a fast response! Well there are 2-3 ways to do it, I will draw it out again and work out which will suit me best. I much appreciate it. Will likely resurrect this post to ask more questions! I am competent at this stuff from diagrams but sometimes struggle to get my head round the relay switching etc.

  6. #6
    Join Date
    May 2016
    Location
    Cheshire
    Age
    53
    Posts
    452
    Quote Originally Posted by Rob P View Post
    Hi James

    You could put a relay (normally closed) in between the dash switch and the connection to the fans. This relay can be operated by either of the thermostat connections to the two fans so when one of the thermostats switches the power to the fan it also supplies power to the relay which opens the relay thus cutting the power to both fans from the dash. In this way the temperature fans can only operate one fan.
    Please see attached a rough diagram.

    Hope this helps.

    Rob
    Wouldn't either thermostatic switch closing power both fans?
    ~~~~~~
    Sumo Mk3

  7. #7
    Join Date
    Mar 2007
    Location
    Maldon Essex
    Posts
    581
    I was just wondering that, Rob, is there something not quite right with that sketch or have I misunderstood? It looks like either thermostatic switch will trigger both fans.

  8. #8
    Join Date
    Jun 2014
    Location
    Swansea
    Age
    58
    Posts
    192
    Yes, you re quite right. You will have to use two relays one for each fan thermostat.

    Rob
    Rob

    AK Gen I - 4.6l Rover V8, Stage III heads, MC1 cam
    On the road March 2019

  9. #9
    Join Date
    Jun 2014
    Location
    Swansea
    Age
    58
    Posts
    192
    Quote Originally Posted by Rob P View Post
    Yes, you re quite right. You will have to use two relays one for each fan thermostat.

    Rob
    Both relays will be normally closed.

    Rob
    Rob

    AK Gen I - 4.6l Rover V8, Stage III heads, MC1 cam
    On the road March 2019

  10. #10
    Join Date
    Mar 2007
    Location
    Maldon Essex
    Posts
    581
    Any chance of a sketch Rob.

Page 1 of 5 123 ... LastLast

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •