Wiring question, White yellow trace?

[Broadstone]

I have a autosparks harness on 1973 series III and would like to know what the white with yellow trace wire branching off the engine harness just before the alternator is for? Did I miss something as I cannot find it in the diagrams.

[TeriAnn]

I have a autosparks harness on 1973 series III and would like to know what the white with yellow trace wire branching off the engine harness just before the alternator is for? Did I miss something as I cannot find it in the diagrams.

That colour combination isn't listed in the '60s colour code I have but it is listed in a 1983 colour code as Ballast resistor to coil or starter solenoid to coil.

Unlike the Americans the British had (have?) a national standard for colour code insulation for different uses. I suspect the autosparks SIII harness is a universal replacement harness that includes wires used for very late SIII trucks. Late SIII coils may be a ballast type coil and the white yellow wire was a way to bypass the ballast while the starter motor was turning as a way to provide extra power to the spark plugs (easier starting).

Just a guess.

[siiirhd88]

On a late SIIA the white with yellow trace wire is for the oil pressure warning light switch.

Bob

[Broadstone]

It is located about equal distance from the oil pres wire and the ends for the alternator. It just seems an odd location. I guess I will trace it back and see what I come up with or just blank it off. I did refer to your site TerriAnn just before posting this question in hopes of figuring it out.

[jac04]

Could it be for the fuel cut-off solenoid on the carburetor?

[scatterling]

it could be for the cold start control switch

[Broadstone]

It will not reach the carb. or the cold start which is already wired up properly. Here is a picture if that helps.

[jac04]

^^Wait a second. In that picture the cold start warning light temperature switch isn't even installed in the head. You just have a blanking plate with 3 screws holding it in place. It looks like the wire would plug right into it if it was there.

[TeriAnn]

^^Wait a second. In that picture the cold start warning light temperature switch isn't even installed in the head. You just have a blanking plate with 3 screws holding it in place. It looks like the wire would plug right into it if it was there.

Except if the truck were fitted with a fuel mixture warning light the wire going to the fuel mixture thermostat switch should be light green/red.

Silly question, where does the other end of the wire go?

Also, why not ask the harness manufacturer where that wire goes?

The problem with a national standard for wire use colour codes is that it gets amended over time and we do not know which version of the code the harness maker is using.

[Broadstone]

Now we are getting somewhere. The choke switch is also white yellow as stated by Scatterling and has continuity between choke switch and the wire in question. Jac, this is my first NADA series truck and my previous home market vehicles did not even have this space to blank off, it was closed as factory I am pretty sure. So what temp. switch do I need? same as the other temp sender? and was it factory only on NADA spec. trucks. Really appreciate the help everyone!!

[TeriAnn]

Now we are getting somewhere. The choke switch is also white yellow as stated by Scatterling and has continuity between choke switch and the wire in question. Jac, this is my first NADA series truck and my previous home market vehicles did not even have this space to blank off, it was closed as factory I am pretty sure. So what temp. switch do I need? same as the other temp sender? and was it factory only on NADA spec. trucks. Really appreciate the help everyone!!

I'm puzzled. You have a 1973 SIII truck. I didn't think they came with choke warning lights. I've always thought it was a SII & IIA thing and didn't appear on a SIII.

I did do a little more research with my SII & SIIA diagrams and it looks like the wires colour code changed for the cold running circuit between the positive and negative earth models. Still didn't see a white yellow though. But it appears the lead you are dealing with is the one that goes between the on/off mechanical switch that activates when you pull out the choke cable and the thermal switch you do not have.

The circuit is switched 12V through the cold running indicator light to the on/off switch which turns on when the choke cable is pulled out, to the thermal switch by the thermostat housing. When you pull out the choke cable, the mechanical switch turns on which allows power to go through the cold running light to the thermal switch which is open when the engine is cold and closes when the engine heats up. When the engine gets warn the cold running light comes on to remind you to push in the choke. When you push in the choke cable you cause the switch on the cable to open turning the indicator light off.

Looks like I will need to add a couple wires to my chart and specify positive and negative earth wiring.

[scatterling]

http://www.land-rover-lightweight.co.uk/Images/Electrical/ImageMineNew.jpg

Here's a picture for reference. Top right-ish side. I know it's a lightweight but the colour codes still apply. I looked a few years back and if I remember correctly the thermal switch was nearly impossible to find.