Need to know where a wire goes

(Hunter Bailey) #1

Hello, I have an unplugged wire in my 1965 Jaguar 3.8 S-Type. I do not know how to read wiring diagrams and was hoping someone could either upload a picture of their own fuse box or tell me where it goes. Thanks in advance. I have more pictures if anybody may need them.

(John Quilter) #2

Here are two pictures of the dash wiring in my 1965 3.8S. I see that the instrument voltage regulator does have some of the nylon right angle Lucar connectors with green wires. Can not tell from your picture what the tracer colors is on yours however on mine there is green and light green/black wires connected to it. Do your fuel gauge and temperature gauges work?

(Hunter Bailey) #3

Thanks for the pics! I cannot even start the car so I’m not sure about the fuel gauges. All of the fuses are good so I was thinking that this wire may be the one thing stopping me from starting it. The wire that is unplugged is on the right side and can’t even reach where your light green/black and dark green are plugged in. It is also wrapped with a red/white and red wire as well. Here’s another picture:

Thanks for your time, anything helps.

(Hunter Bailey) #4

Here’s a bigger picture for reference, I think our wire colors are pretty identical:

(Andrew Waugh) #5

Are the wires just Green, or Green with a White tracer?

Green/White would be flasher lamps, RHS.

Green would be ignition switch fed auxiliaries (Wipers, gauges, anti creep etc.).

If your car is an automatic and won’t start, then the loose wire may be the feed to the transmission interlock switch. Otherwise a Green, or a Green/White wire being disconnected should not stop the car from starting.

(Hunter Bailey) #6

Yes, it is a solid green wire and yes, it is an automatic.

(Andrew Waugh) #7

That being the case, and the fact that it’s a double wire connector, then it’s probably come off fuse 3.

If the heater fan also doesn’t work, then that would be another strong indication.

How many green wires come off fuse 3?

(iirc the schematic isn’t perfectly accurate - some of the daisy chained connections aren’t shown where they appear physically in the loom.)

(Hunter Bailey) #8

I don’t think it can even reach fuse 3, which has 2 green wires on it.

(Andrew Waugh) #9

Fuse 3 should have:

Horn Relay
Screen Wash
Stop Lamps
Reverse Lamps
Overdrive or Automatic features

Fuse 4 should have:

Fuel, Oil, Temp gauges
Heater blower

Which of the circuits listed above do NOT work with that wire disconnected?
(I was wrong about the heater in my post above)

(Andrew Waugh) #10

Looks like 3rd switch from RHS, Lower Right corner

(Hunter Bailey) #11

Okay great, that definetly looks like where it goes, thanks a ton, Ill get back to you on which of the fuses work.

(Hunter Bailey) #12

Okay the only thing that works is the headlights and a left arrow on the screen above wheel. That’s all, and those things can work without the key even being in so I’m wondering maybe its something wrong with the key tumbler itself. Also the starter push button does work from the engine bay.

(Richard Greene) #13

EXCELLENT thread with pics! It brought back memories of the “old” Jag-Lovers! I wish more were like this instead of someone saying “look in the manual”. I just bought a Bentley Arnage and so far, the Bentley forum is almost useless!


(John Quilter) #14

You may have two issues here. If the starter does not turn when you push the black rubber button at the end of the starter relay at the back of the engine compartment there must be an issue with the cable from the battery to the relay or the cables from the relay to the starter motor itself. Or a dead starter motor. The cables are both heavy black cables.

(Hunter Bailey) #15

The black rubber button does work so I’m definetpy thinking ignition.

(tony) #16

place a test light into the unattached wires and press start button…if they light or do not, this will indicate if this is causing the “no start” problem… or you have another issue entirely

This is also a good time to learn to read a circuit diagram. A tiny bit of application is worthwhile

I earth my test light on the ignition key

(Hunter Bailey) #17

Thanks for feedback, I will definetly try that out

(TOC) #18

I recall on another British Car Forum somewhere…I suggested using a test light and some person seemingly appointed by the most high Himself got all over my carcass about telling folks to work on live circuits with a test light. Good to see there is more reasonableness here.
ESPECIALLY Limey Limos respond well to test lights…unless said test lights are made by Lucas.

(tony) #19

not sure why?..surely cant have been safety?

There is a few issues.

  1. what Impedance/resistance is presented to the circuit by the test device…so I DONT recommend test lights on electronics…use a multimeter…they present M-Ohms resistance…IF set on the correct range…(I did once blow something up using a multimeter mistakenly set to amps which is a short circuit)

  2. on our Jags a test light is better imo, as it is easier, and also will only alight when ~60ma flows, so will often be helpful with old connectors and so forth, where a multimeter may in fact show 12V, but at micro amps. A test light will present sufficient resistance to a non-electronic circuit

If the chastisement was due to the possibility of shorting parts with a probe …be careful

It is possible to use the ohmeter function of a multimeter to trace non-live circuits, but this is more difficult. My mate who is a retired auto electrician would go insane if I ever mentioned Ohms in auto fault finding

my qualifications and experience were with electronics & mechanical.
I found different ideas & methods between auto-electrics, HV, and electronics