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SP New wiring loom problems

Big Col
Posts: 475
Joined: Tue Feb 16, 2016 12:45 pm
Location: Leeds

Re: SP New wiring loom problems

Post by Big Col »

I had problems at the rear end when I fitted a new Autosparks loom.
In my case I found that swapping the positive black cables in the boot area work to cure the issues. I don’t understand the black art of electrics but it seamed as though the fuel gauge, pump and reserve solenoid mattered as to which wire fed them. It was not exactly obvious which fed which as they are not labelled and the lengths are not obvious. Anyway through swapping them around I had success and no more problems.
I may be slow but I’m rough as well !

John Chatfield
Posts: 45
Joined: Mon Feb 22, 2016 11:00 pm
Location: Shrewsbury England

Re: SP New wiring loom problems

Post by John Chatfield »

Hi folks, I don't know if Tim has solved his problem but I have just noticed on Auto sparks site that if you are fitting an alternator you may have to take the ammeter out of the system as it can wreak havoc, just an idea if you are fitting an alternator it may be worth looking at their site or giving them a call.

Posts: 61
Joined: Sun Nov 19, 2017 10:45 pm
Location: Warsaw Poland

Re: SP New wiring loom problems

Post by Zbigmak »


Can you remember where is the rear earthing point is on the Dart as I do not seem to have one or rather cannot seem to find where it should be
Sydsmith wrote:
Wed Oct 02, 2019 2:17 pm
In DC electrics there always has to be a positive and negative feed to what ever you are intending to operate.

In a conventional metal bodied vehicle that is fairly easy to achieve. The metal body is used as either the positive or negative lead and is commonly called earth. The other feed is provided by individual cables to each item that requires 12 volts, the item say the fuel pump has another lead connecting it to the body or chassis. We won't go into the reason why there have been changes between positive and negative earth vehicles over the years, suffice it to say either will do.

The SP has a special problem in that it has a glass fibre body which as it is a good insulator will not of course conduct electricity, so cannot be used as the second lead. To provide the necessary second lead or earth, there needs to be special arrangements in the wiring loom to ensure an earth is available throughout the wiring system where it is needed. If you don't understand electrics and are fitting a new loom for the first time, it does not get much more difficult than a glass fibre vehicle.

In the case of a positive earth vehicle, the positive battery terminal is connected directly to the chassis and the engine block and drive train are also connected either directly to the positive battery terminal or via a thick lead to the chassis.

So in an SP250 wiring loom as you have discovered bigmak you are going to find lots of earth leads to make up for the lack of a metal body. On the SP there are common points for the earth connection and they are and several can be bunched together on one point and an earth return taken back to a central earth or to the chassis.

I don't have my SP wiring diagram to hand but from memory you will see there are several leads the connect to the chassis at the front and back end of the vehicle. Hope that helps. Syd

Posts: 64
Joined: Wed Sep 21, 2016 8:29 pm
Location: Bury St Edmunds

Re: SP New wiring loom problems

Post by gc0700 »

I sorted of solved my problem, insofar as I identified the pale green wire that should go from the flasher unit to the indicator warning lights, does not do so. Seems like there is a fault with the brand new loom on just this one wire, as everything else works OK. The warning lights, I just connected to earth and they now work as expected.

I've also now fitted LED lights (from http://www.dynamoregulatorconversions.com/) and am seriously impressed by their brightness.

On the rear earth question, I don't have a connection at the rear of the car to earth. The loom has (or should have) black wires, fed to either side of the boot/trunk that provide an earthing point.

Big Col
Posts: 475
Joined: Tue Feb 16, 2016 12:45 pm
Location: Leeds

Re: SP New wiring loom problems

Post by Big Col »

Zbigmak, I hope Syd will confirm, but I don’t think there is a common earth point at the rear. As far as I remember, the loom carries earth wires as well as supply wires. I think that is why when I swapped them around the different components, as mentioned in my previous post, it cured my problems.
I may be slow but I’m rough as well !

Posts: 217
Joined: Tue Feb 16, 2016 12:35 am
Location: Arizona, USA

Re: SP New wiring loom problems

Post by Ozzsp250 »

On my car there is no single point for ground or earth either, as stated carried in the loom by multiple black wires to each side of the car. I did have a erratic fuel gauge and suspected it to be a grounding issue. I ran a 12 ga. black wire from the chassis to the fuel tank [aluminum in my case] and it resolved the problem.

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