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Thread: Roadster Electrics

  1. #1 Roadster Electrics 
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    Hi All

    I have mostly completed the rewire of my Roadster and I now have the engine running for the first time in twenty years. The Water Pump Gland has decided to shows its displeasure by weeping but I will run it fore a while to see if it settles down, if not I'll change the Pump before I put it back on the road.

    I have fitted a new Alternator supposedly for the Marina 1800 TC Engine and having checked its output voltage I'm getting 14.6 volts measured at the coil input connection. In the grand scheme of things I don't see to be a problem but I want to fit an Acuspark Electronic Distributer and the installations instructions state the the input voltage to the coil should not exceed 14.2 volts max otherwise damage to the unit will occur. Does anyone know how to reduce/regulate the voltage down to the correct voltage, as anyone else fitted an Acuspark Distributor?

    Another strange occurrence that is happening is when I stop the engine. I have fitted an Electric Radiator Fan controlled through a Temperature Switch built into the top of the radiator and its 12v supply is through an Ignition Switch Controlled Relay and it all operates as it should ie the fan kicks in at the control temp and the fan runs until it reaches the cut off temp and stops and so on whilst the engine is running.

    However the problem that I have is that if I turn the ignition off whilst the Rad fan is running the coil voltage drops to zero as expected but the engine keeps running for about 2 seconds then stops but when the Rad fan is not running the engine stops as normal. Incidentally before I installed the ignition controlled relay the engine used to keep running for 4/5 seconds.
    The solution's that I'm working around is to not stop the engine whilst the fan is running or even fitting an on/off switch in the fan supply to stop the fan just prior to turning the ignition off.
    Has anyone else encountered this strange occurrence before and what could be possibly causing it?

    Regards to all.

    Mick.

    Fngine Run Up.jpg
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  2. #2 Re: Roadster Electrics 
    frequent forum contributor Club Member greyV8pete's Avatar
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    The fan motor is a permanent magnet type. I believe that if it is still spinning it will be acting as a miniature dynamo generating a small reverse current which is just enough to energise the coil and keep the engine running for a couple of seconds until the fan stops turning. I would be considering fitting a diode in the fan circuit to prevent this happening. It will also safeguard the electronic distributor.

    When cooling fans are wired without a relay a similar thing happens when the car is travelling forward. The windmilling fan generates this small current and the fan warning light will glow.
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  3. #3 Re: Roadster Electrics 
    club member Club Member Tony Stott's Avatar
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    Ha ha, I view a piece of anvil rail i I have a similar piece, mine came from the Prettywood incline between Bury and Heywood, my dad started as a platelayer on the line way back when!!
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  4. #4 Re: Roadster Electrics 
    club member Club Member chris_cussen's Avatar
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    Fit a diode into the feed to the fan. It will block the output from the fan when the engine is turned off. Something like this from Ebay https://www.ebay.co.uk/itm/283186713...MAAOSwiN9auAI8 10Amp Schotty diode. Costs less than £2

    After you fit it if the fan does not work turn it around.
    Cabrio, Omex 2.0l 170bhp Zetec blacktop, Omex ECU and wiring loom.
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  5. #5 Re: Roadster Electrics 
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    Hi Guys

    Thank you for your rapid responses and solutions I have now ordered a couple of diodes, do I solder it in line and then cover it with heat-shrink wrap, once I've determined that it is the right way round doe's it damage it if you initially install it in the wrong way round?
    It also sounds like a solution to another problem that has arisen. I have installed a switch operated fuel cut off valve in the fuel supply line (from CBS) and again that all works as it should until the ignition is turned off then (on checking with a meter) everything goes down to earth so it looks like a diode in the live supply with sort that issue as well.

    I still don't know what to do about the alternator over-charging. I have ordered a new battery today as up to now I've been running it via jump leads from the Cabrio so the jump leads might be causing a false demand on the Alternator for increased charging voltage. As you can tell Electrics isn't bag I'm Mechanical but then again neither was paint spraying a mechanical discipline but I got through that ok so provided I don't do any damage I'll keep on (as in the Marlin Owners Club spirit) giving it a go!

    Thank you again guys,

    Mick.
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  6. #6 Re: Roadster Electrics 
    club member Club Member chris_cussen's Avatar
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    Hi Mick,
    The diode is just like a one way valve,it just lets electricity flow through it in one direction. Connecting it 'the wrong way round' will not damage it.
    Your other problem with the fuel cut off sound like its the same cause.
    To be honest I wouldn't worry too much about the small overvoltage for your distributor. I would expect that they would design it with an adequate safety margin.
    If you want to be sure that it does not exceede 14.2v then you can put a resistor in line to its supply, but the value of the resistor will depend on the current required for the distributor, so the first step would be to measure the current drawn by the distributor, then do some maths to work out the resistor value.
    Cabrio, Omex 2.0l 170bhp Zetec blacktop, Omex ECU and wiring loom.
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  7. #7 Re: Roadster Electrics 
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    Hi Chris

    Thank you for that information. It's certainly food for thought about the voltage and the resistor value, although measuring current draw and working out the resistor value is beyond my skills I'm afraid.

    Kind regards

    Mick.
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  8. #8 Re: Roadster Electrics 
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    Hi Tony

    Yes a nice piece of Vignoles Rail always comes in handy for working metal or weighing something down. I have a slightly longer piece as well. I painted the sides with Record Vice Paint to make them look like pukka workshop equipment. I came by them several years ago whilst on Holiday. I was watching these guys lay and fit rail on an Heritage Railway and having cut a pair of rails to length they then Rota-broached the bolt holes for the fishplates. I asked the guy what happens to the offcuts and he said that they are thrown in the Cess and maybe collected for scrap once the rails are in use. When I asked if I could have a scrap offcut he said that he couldn't give me any but if it disappeared overnight its nothing to do with him (placing them at the side of the fence for easy reach). So they disappeared during the night.
    When we visited the Railway Centre the following week I put a suitable donation in the collection box as I am an Heritage Railway Fan anyway.

    Regards

    Mick.
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  9. #9 Re: Roadster Electrics 
    club member Club Member chris_cussen's Avatar
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    Hi Mick
    If you have a meter that can measure amps and you want to have a go then I could generate a set of instructions.
    Chris
    Cabrio, Omex 2.0l 170bhp Zetec blacktop, Omex ECU and wiring loom.
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  10. #10 Re: Roadster Electrics 
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    Hi Chris

    Thank you for your offer of help with this problem.

    I have checked my meter and it only reads up to 10 Amps max for 15 seconds I wouldn't think my coil will come anywhere near to 10 Amps, I try and take a reading next time I run it up and I'll let you know.

    Kind Regards

    Mick.
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