Electric tester.

[oldherbaceous]

I don't know if anyone has a easy way of describing the following for me...
I want to do a resistance test on some wiring on my Kubota tractor 12volt DC, to see if i have a short or a broken wire. I have bought a tester but i can't get to grips with the very limited instructions. From what i can gather, i connect the red and black leads onto the ends of the wire i am testing, using the ohms setting, but what it doesn't say is, at which level. It ranges from 200, 2000, 20k, 200k and 2000k.

Also should it read 0 ohms for both a broken wire and a short?

I'm fine if i'm shown something like this in a practical way, but i do stuggle to to understand things off instrutions, so, any help would be very much appreciated.

[Geoff]

On mine there is a dial where I select what I want to test like V DC, V AC, Ohms. There is also a continuity option with a symbol of two arrows pointing to each other and something that suggests a noise - if you select this and touch the two probes together you get a beep. You can use this to test for your broken wire - no beep for where it is supposed to be going, or perhaps a beep on the chassis if it is shorting out to somewhere. This also displays as a kohm scale, showing 1 when the probes aren't touching, something close to zero when they are, something in between probably indicates a leakage or partial short. The ohm scale behaves the same but without the beep. Does that help?

[oldherbaceous]

Morning Geoff, thank you for the reply, it does indeed help... mine doesn't have the beep mode what is quite annoying, so i'm having to go on the kohm digital read out. But it is now, which one of the figures i mentioned in my previous post, that i should be using?

[Cider Boys]

Hello Oldherbaceous

To measure a resistance you select the ohms range depending on what amount of resistance you are expecting to read. Therefore you would select a high range say 20k to read a resistance of for example 15k, if you had selected the range up to 2000 (2k) then the meter would not be able to read a 15k (15000) resistance since it would be above its 2k limit. So the different ranges display the maximum resistance it will measure up to. Therefore the 200 range will measure resistances between 0 and 200 ohms and 20k range will measure between 0 and 20,000 ohms. However if the resistance you were measuring was 100 ohms it would read it more accurately on the 0-200 range than the 0-20k range.

If you are looking for continuity between one end of a wire and the other end it should have a low resistance (close to zero), so any range will measure that but the lower range (200) would measure it more accurately.
Therefore select 200 and touch both meter leads together and it should display a steady reading of the resistance of the meter leads (close to nought). Then apply each lead to the two ends of the wire you are testing and the meter should again display a little above nought and if it does then the wire will be proved to have continuity between each end and not be open circuited (broken). If it were open circuited you would not get a steady low reading.

If you need to measure if there is a short circuit to earth (chassis earth) in the length of wire you will need to connect one lead to the chassis or engine block and the other lead to the ends of the wire in question. If the wire is shorted to the chassis earth the meter will display the resistance to earth measurement. You may need to try it through all the ranges to check that there is not a high resistance short to earth.

What you want in a length of wire is a metallic link from one end to the other and that it is insulated from any contact with anything else.

Therefore you want to see a low resistance (close to nought) path from one end to the other end to prove its continuity and NO resistance reading at all when measuring between the wire and anything else it should not be in contact with.

I may not have explained this very well, Oldberbaceous, and if you want any clarification please don't hesitate to ask.

Best wishes

Barney

[oldherbaceous]

Afternoon Barney, what a wonderful reply, it's exactly what i needed and i know what i'm doing, now, so a big thank you for taking the time to explain things in the easyiest way possible.

I might be back with more questions, as i have also got to find out why the indicators aren't working...so a few more things to try and check out, combination switch, flasher unit and a few juntion clips.

[Ricard with an H]

Isn't it just terrific the things we can ask help for on this forum, what is more 'terrific' is the lack of b-xhit.

Well done for the simple explanation Barney. OH, can I suggest during these often nasty wether days and nights you go for a basic self-tuition on the this subject and on OHM's law which is very relevant to many maintenance problems we/some of us come across. It seems difficult but it's actually very simple.

For many years as a young man who couldn't afford a meter I used a battery/bulb combination soldered together to whatever insulated wire you can find. If it's floppy wire you just need to solder a makeshift probe on the ends. When the bulb lights up you have a circuit, if it doesn't this is known as 'Open circuit'.

Our motorhome has presented one or two problems over the years due to poor electrical weather-proofing, at 12V it doesn't take much to go high resistance which behaves like an open-circuit at low voltage so I have a 30 foot set of test leads attached to a battery and a bulb for finding faults.

[oldherbaceous]

Afternoon Richard, we are lucky to have such wonderful members on this small forum. And it never cease to amaze me, the time and effort some people will put in to answering quite difficult questions.

I think i have now got to grips with what i need to know, and actually have got all the electrical problems sorted...well i hope so.
One problem that did get me very frustrated was, trying to get the indicators sorted. they weren't working at all and most of the wiring was very hard to get at, without taking the whole loom out from behind the dash.
But after cleaning all the joiners and testing the switch and flasher unit, i managed to get them to burst into life. The indicators are a funny set-up, with them being back to back, one facing forwards the other facing backwards. These have seperate bulbs in for the indicators, as well as a side light bulb in....anyway, i kept getting the side light flashing in one of the lights, but after spending ages and ages, testing and swopping wires, i finally found although one light was earthing ok, the other one just relied on two fine connecting screws to supply the earth for the other one. Although the screws looked like new, they still weren't making a good contact...I might run a seperate earth wire to them sometime...

So all in all, i feel rather contented...

[Ricard with an H]

So all in all, i feel rather contented...

Well-done and I do know how difficult 12 problems are to solve. The reason I mentioned understanding OHM's law is that you can test a circuit at 12 volts that isn't OPEN, it's showing 12 VOLTS but it isn't passing enough CURRENT because of the RESISTANCE so rather than prove a circuit sometimes it is essential to read the RESISTANCE in the circuit.

I now spray anything electrical I come across with contact spray, sometimes I coat around contacts with vaseline or silicone grease and sometimes I use wax spray. What you're doing here is cutting down on electrolytic action between dissimilar metals and/or the effects of water and salt.

The reversing switch on some vehicles is always a problem and usually difficult to get at, this will show up by the reversing lamps and parking sensors not working. I used to have a habit of leaving any vehicle I drive in reverse gear when parked, I think this added to the problems I had with reversing switches.

Happy new year.

[robo]

I realise you are working on a tractor but, when we bought our fishing boat me and my mate the joint owner decided to rewire all the gauges ,batteries, starter motor the lot, i did it a bit at a time or should i say one gauge at a time including all the ignition wires, i did it over about 3 weeks but i always had problems with different things working ok one minute and not the next, in the end i started soldering every contact no problems since i also covered the soldering with shrink tube that has an adhesive inside

[Ricard with an H]

always had problems with different things working ok one minute and not the next, in the end i started soldering every contact no problems since i also covered the soldering with shrink tube that has an adhesive inside

Oh-yes, do you know those ScotchLocks they use for making connections for the the trailer wiring to a car ? They cause a lot of problems because of corrosion, the plates that cut into your wiring when you press the ScotchLoock closed must be steel. Add water to steel touching copper and you get electrolytic effects, the steel becomes sacrificial and the circuit breaks.

Robo, I also solder everything I can get my hands on but my Lidle soldering iron has packed up today. Bummer.

Ask me if I know where the receipt is ?

[Pa Snip]

Ask me if I know where the receipt is

I can tell you....................

Its in a place where you will find it just after you have purchased a new one

[Cider Boys]

Whilst I would agree that to solder wires together can be good practice. A few points need to be considered, solder has resistance and should only be used to make a good mechanical joint. Therefore if joining wires you need to clean them (do not let sweat from your hands get onto bare wires) and then twist them together so they are in good contact before tinning them with solder. I would not advice anyone to tin wires that are going under a screw such as in a domestic 13 amp plug, the will work loose over time and become high resistant and hot. It is permissible to tin the very end of a muti-wire to keep the strands together but do not let solder run up under where a screw terminal will press down on the wires.

As for using 3m Scotchloc, insulation displacement connectors you must use the grease filled moisture resistant ones if using externally or if in any damp conditions.

Barney

[Ricard with an H]

Thanks for that Barney, I didn't know about any other ScotchLocks than the common ones used to connect mostly inside the car under the boot lining though they are also used in just about any situation by fitters and mechanics who have little knowledge about the frailties of 12 volts and atmospheric effects on dissimilar metals.

the tip about twisting wires that are to be soldered is often either unknown or ignored for convenience and you'll often see 12 volt wiring just touch-soldered.

Pa-Snip.

To be honest, I probably didn't even keep the receipt though I can't explain why I don't just slide it inside the instruction book which then goes into a plastic wallet.

You can only lead the horse to the water, Eh ?

[robo]

Im that good at soldering that i have to twist the wires together other wise i usually solder my thumb