Cable Tracer & Tone Generator

[AndyW]

Anyone used a cable tracer & tone generator for tracking wiring and continuity around a car loom? I wonder whether it's worth getting one to help me understand where all the wires go on my SuperSpec. Any recommendations for a cheap test unit?

 

[knights_templar]

Yes, and it works in a fashion. The proper professional ones are in the hundreds, but I picked up a telephone one for under 20.

 

If the wire you are following is bundled with a few cables its fine, but the signal faded if there are a lot of wires together.

 

There is also cross feeding, in circuits, for example a live wire to a unit will have a return or ground wire that will often run in the same loom to a common grounding point on the chassis, there are three in the Vicky Green, the sensor will pick up both sides of the circuit, and often the chassis, so you have to remove the load from each circuit and possible earth points.

[AndyW]

I see there are some cheapish ones on eBay intended for phone and network cable checking. eg. http://www.ebay.co.uk/itm/262547785522

 

Just wondered how well they worked on 12v car looms and particularly if they would help me identify where ground wires go round the loom and where they come out to fix to the chassis.

[knights_templar]

You need one with clips to connect to the wire, mine works as a signal generator, as above, but I found the continuity check feature of the signal unit to be as, if not more, helpful.

 

In terms of ground wires, probably no good unless you know where they are and can disconnect them from the chassis.

 

On the VG the connection points are front, front of chassis, mid, dash area, and rear around diff area. You can never be more accurate than that on the robin hoods, earth connections had to be made by the builder, Tay were not provided as points on the chassis and builders could run the loom in different ways.

 

To be fair it is not really necessary to find the earth points, just to know they are OK. That can be done with a ohms meter by checking the black wire on any load point, it has continuity with the chassis it's OK. The circuit feeds are relatively simple to track if a single circuit. The oil pressure sensor wire wold go to the clump of wires intended for the dash, as would the alternator sence wire, switched circuits would end at the witch gear, although headlight relays, and colour changes are thrown in to mislead.

 

BC is a simple loom, there are a few versions, to meet the needs of the donor car but they all follow basic rules.

 

Brown constant live (battery)

Black. Ground

White. Ignition live from fuse board, but feed by white on ignition switch.

Green. Ignition live, brake and reverse rpm fuse board

Red. Side lights

Can't remember mutch else off the top of my head, would have to find my diagram.

 

But don't forget the case loom is often moded.

Edited November 21, 2016 by knights_templar

[fry61]

BC is a simple loom -- did Fred & Barney have lights on their wheels!!

[knights_templar]

no b&*$$y spelling correction on my pad.

[Guest Gargoil]

The tone and generators are good bits of kit, its the wiring loom that makes things difficult, with common/multiple earth points.. As said above, use the tone and amp to trace a wire but confirm it with multi-meter.

[AndyW]

Helpful info, thanks K_T and everyone.

 

Presumably much of my loom is VG as came with the kit from RHE, but I'm told the car was wired by an "auto-electrician". Let's just say I'm not impressed by the workmanship - there are many additions and alterations that have all been done in the same red, green or brown colour wires, and some wires change colour when they come out of a batch of insulation tape. Also there are masses of wires just bundled and taped up, so I'm not sure if they are used or not. And there are many odd black wires screwed to the chassis at various places around the car, more than the 3 grounds marked on the wiring plan - I want to know what piece of equipment they come from.

 

What's confusing me is there multiple similar green and red coloured wires around the loom, but I only seem to have 2 fuses for each, so I don't know how all the wires join up. All that makes it near impossible to determine what wires are going where and what they are connected to.

 

I've been offered loan of a tracer and tone generator, so looking forward to trying it to see if it will help me explain my wiring system.

[AndyW]

I't would help if I could understand how professionally made wiring looms are put together (a Vicky Green loom in my case). Where there are multiple common wires how are they joined together? I'm trying to visualise the physical layout.

 

For example, I have a green/red wire coming from the indicator stalk switch which goes into the central loom. Then there are 3 other green/red wires that come out of the loom in different places on the car - front left indicator, rear left indicator, and at the warning lamp in the dash. How would those 4 wires be joined in the loom?

 

Is there some sort of master connector somewhere, or are they all soldered together in one place, or in several different places in the loom?

[IanS]

normally soldered or crimped.

In your example I would expect 2 joins, one behind the dash to the warning light and one at the side of the car to go to the front and back.

Actually I woukd expect a third to the side repeater.

[Dave R]

you say about same colored wires... mine are all black

[Dave R]

if you need a hand at all, dont think i am that far away from you

[fry61]

Why complicate things Andy? All testing can be done with a simple 12volt lamp -- connect a high wattage lamp (head-lamp bulb ) one side direct on positive of battery & other lead to the battery lead/leads normally connected to the battery post. Testing can now be done without fear of a short or blown fuse. If a lamp or motor is part of the circuit being tested it/they will glow or run slowly -- relays may just click in & out as voltage drops with load. To find which parts of the chassis or component are effectively earthed --take a flying lead from the load side of the test lamp & touch down on any metal or contact. The cars lamps need to be removed to prevent false readings for this.

[AndyW]

Thanks again Ians and FMW for all the suggestions. Useful.

 

DaveR - thanks muchly for the offer, though I don't think it's necessary at the moment.

 

I don't have any problem with the actual electrics in the car, this is more an intellectual excise of trying to understand my wiring. I'm drawing up a proper wiring diagram/schematic as a winter project. So far I've got all the electrical parts plotted and tracked the wiring routes and colours in the looms from ECU, engine sensors, and front and back of the car. I now have loads of wires on my diagram that all head into the central firewall & dash area that I need to make sense of. I need to work how the battery joins to the ignition - then to the fuses - the switches - and on to the components.

Edited November 25, 2016 by AndyW