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Thread: Are you using ignition relays on your build?

  1. #1
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    Are you using ignition relays on your build?

    Are you using ignition relays on your build?

    I mean relays that engage when you turn the key to the first position (power to accessories),
    and for the second key position (ignition) engage a 2nd relay(?), to take the load off the key switch.
    Is that how you set the wiring on your car?

    The relays would be engaged/powered for hours at a time on a long run,
    are special relays required? any burn-out issues?

    Any advice for setting up this part of the wiring loom?
    The 2nd position relay would need to be big, capable of powering the car; >30A, how big should it be?

    Interesting that the CBS Wiring Module doesn't appear to use them(?)
    https://www.carbuilder.com/uk/cbs-12...-wiring-module

    I am using a Ford Sierra column and ignition switch, not the 'stock' VW one, if that makes any difference.

  2. #2
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    It kind of depends on what you are switching first position accessory's radio gauges then no second position on a standard VW no but you have an electric fuel pump so yes. the coil on a relay takes very little current and are run for hours without any issue. I think I have relays for fuel pumps head lights wipers and headlight flaps.

    Dirk

  3. #3
    Senior Member Phill's Avatar
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    I used hardly any relays in my loom. And instead of a key switch on my car I just used a simple 30amp rocker switch that provides the power to a fusebox which then feeds the coil, starter switch, indicators, brake lights. windscreen washer, wipers, oil pressure light, instrument lights, rev counter and level gauge.

    A separate fusebox wired directly to the battery feeds the lights and horn (which itself uses a relay), hazard flasher. This means that the lights can be accidently left on when the ignition switch is off so I would probably do it differently if wiring the car again. The horn is available at all time as is the hazard warning lights.

    The roof mechanism is fed direct from the battery and uses a changeover relay and a starter solenoid to handle the big current.

    My original intention was to use the CBS module as this seems to take car of everything and is a nice neat solution. However, they were out of stock at the time I was doing my wiring so I had to improvise my own, but had it been available I would have used it instead.
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  4. #4
    Standard 12v 40Amp relays (4 or 5 pin) will be more than enough for most functions in a normal set up.

    I use relays for headlight operation because of the 'pop up' nature of the units and operating a wiper motor (LR2) as a lifter motor although it doesn't take a lot of amps and is not 'on' when the light are up, it does involve micro 'stop' switches.

    I also use one to engage main beam from default dip using a single wire, like VW and another switches off the DRLs when headlights are on (as required), so mainly for light logic circuits.

    The doors (canopy) auto open/close are 4 x Lucas 40A relays which work as change over switches, from the 4 radio control 10A on board relays although the actuators are only rated at 4A and only when moving,

    Starter is a button system, ignition is activated by blue tooth with my phone being nearby and the brake light on, also starts the engine automatically via an 80A relay before the starter solenoid but that is to hold the power on until the alternator kicks out 12v at which point 12v +12v = 0V.

    So yes, I use relays. In a normal car the 2nd or ACC (+15) circuit is for minimal services such as radio and shouldn't need more than a few amps in total, relays would be used to relieve load on switches or to 'change state' such as the 5 in my 1987 BMW E30, which includes one for the fuel pump which gets a signal from a pressure switch to start pump when pressure falls below a set limit ensuring the system always has a pressure supply but not when it's not needed

    There I go again, you asked the time and went on about building a clock.
    Last edited by Peter; 19-12-2019 at 11:28 AM.



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  5. #5
    I am in the process of rewiring my eagle SS from scratch.
    I used relays for both the coil and starter solenoid.
    I plan to use relays for headlight motors (pop-ups) and the lights themselves.
    Ill put fuses on all supplying wires. Even the big cables to the starter itself.

    Reading up on the VW T1 electrics (a bit of googling), you will see various articles on the gremlins caused by the key switch burning out and wires not being fused.

    My thoughts...
    The VW T1 wiring has worked for a considerable amount of time. I'm sure key switches have lasted decades under normal use.
    The fuse system somewhat works, beetles are not known for catching fire due to electrics.
    Fiberglass cars have less chance ground shorting.
    It's unlikely a kitcar will get the same level of use as a daily driver.

    However, if you are in the position of rewiring a section of your car.
    Relays cost in the region of £2. Thin wall wire is £15 for 50m. Fuse box is less than £5.
    Thick gauge cable (starter motor and solenoid) gets expensive.
    If you can position your battery close to the engine, you can drastically shorten the starter and solenoid cables which helps in keeping the cost of cable down and also reduces the voltage drop on the cable.
    Last edited by ChrisBailey; 19-12-2019 at 01:37 PM.

  6. #6
    Quote Originally Posted by ChrisBailey View Post
    I am in the process of rewiring my eagle SS from scratch.
    I used relays for both the coil and starter solenoid.
    I plan to use relays for headlight motors (pop-ups) and the lights themselves.
    Ill put fuses on all supplying wires. Even the big cables to the starter itself.

    Reading up on the VW T1 electrics (a bit of googling), you will see various articles on the gremlins caused by the key switch burning out and wires not being fused.

    My thoughts...
    The VW T1 wiring has worked for a considerable amount of time. I'm sure key switches have lasted decades under normal use.
    The fuse system somewhat works, beetles are not known for catching fire due to electrics.
    Fiberglass cars have less chance ground shorting.
    It's unlikely a kitcar will get the same level of use as a daily driver.

    However, if you are in the position of rewiring a section of your car.
    Relays cost in the region of £2. Thin wall wire is £15 for 50m. Fuse box is less than £5.
    Thick gauge cable (starter motor and solenoid) gets expensive.
    If you can position your battery close to the engine, you can drastically shorten the starter and solenoid cables which helps in keeping the cost of cable down and also reduces the voltage drop on the cable.
    Should have done that, not used 4 meters of very heavy cable from front boot to starter. too late now.



    The opinions expressed in my posts may not be made in a sound mind and should be taken in the spirit intended, Jack Daniels is fine.
    Some people see things as they are and ask why? I dream things that never were and ask, why not?” JFK

    http://ukhozi.page.tl

  7. #7
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    Hi Steve - I'm not using ignition relays, but as the others have said I do use relays for all the heavy load items (headlights, horn, wiper motor, canopy hydraulics). Sidelights are not relay controlled but are on a separate circuit to the ignition. So all that is left is the ignition circuit itself (drawing about 4A in operation), the instrument pod (fused with a 5A rating so I guess 3A at a pinch), the Nav computer, which probably draws a couple of amps, Telecam monitor (<2A) and the heater fan, which I reckon draws 4A at full chat. So what does that give us? About 15A, not really enough to warrant a control relay...

    Lauren
    only Pythagoras can save me now!

  8. #8
    Ive not tested it myself, but reading on the samba, the starter solenoid draws 11 amps after it engages and 22amps before.

    The key switch will handle it, but its a common point of failure.

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