Discussion
Hi all,
Wondering if anyone has any tips/gotchas for replacing a wire with high resistance, my plan is to tap into either end and just lay an overlay but leave the original connected. Also gauge is small.
Background is we have a Discovery Sport that threw a charging error, quick multimeter test confirmed alternator wasn't producing any charge. It's a a pig to change, so sent it to the local garage who replaced with a reconditioned unit. Car now produced 13.6V constantly but still had a charging error. I got the workshop manual and read the codes and got a Land Rover specific one that pointed towards a LIN bus error, the alternator is a "smart" one and gets told how much current to produce by a gateway module.
Did various testing and at first thought the LIN wire was OK as a continuity test showed all good. I have tried various other things but everything pointed back to this particular issue so I decided to test again today, the wire is now showing high conductivity so looks like my original testing wasn't very good! (I have to use long wires as the alternator is at the front of the engine bay and the other end of the loom is in the passenger footwell so reading the meter is hard)
My plan is to lay an overlay wire to eliminate the original wire but struggling to think how best to do it, I can access the wire OK on each end but its only a .5mm wire so pretty small. I'm assuming I am best of cutting the ends and just soldering a new wire on?
Any ideas/tips and tricks gratefully appreciated.
Wondering if anyone has any tips/gotchas for replacing a wire with high resistance, my plan is to tap into either end and just lay an overlay but leave the original connected. Also gauge is small.
Background is we have a Discovery Sport that threw a charging error, quick multimeter test confirmed alternator wasn't producing any charge. It's a a pig to change, so sent it to the local garage who replaced with a reconditioned unit. Car now produced 13.6V constantly but still had a charging error. I got the workshop manual and read the codes and got a Land Rover specific one that pointed towards a LIN bus error, the alternator is a "smart" one and gets told how much current to produce by a gateway module.
Did various testing and at first thought the LIN wire was OK as a continuity test showed all good. I have tried various other things but everything pointed back to this particular issue so I decided to test again today, the wire is now showing high conductivity so looks like my original testing wasn't very good! (I have to use long wires as the alternator is at the front of the engine bay and the other end of the loom is in the passenger footwell so reading the meter is hard)
My plan is to lay an overlay wire to eliminate the original wire but struggling to think how best to do it, I can access the wire OK on each end but its only a .5mm wire so pretty small. I'm assuming I am best of cutting the ends and just soldering a new wire on?
Any ideas/tips and tricks gratefully appreciated.
You need to understand what's wrong with the existing connection and where it is.
It may be a bad connection, or a corroded wire, or some combination. It might be some other fault causing the wire to carry more load than it was designed for.
If you can trace it to a specific wire (as opposed to the terminals and/or connections at either end) then the preferred approach to replace it would be to remove the wire from the connector at each end and replace the whole wire. If you can prove there's a failure within the wire itself, for example due to external damage, then it's reasonable to cut out the damaged section and splice a replacement in. Make sure you route the replacement the same as the wire it's replacing, get the length right so it can't pull tight, add strain relief around the joint and re-loom/re-wrap as appropriate. Heat shrink self sealing colder/crimp connectors make it very easy to get a good joint protected from the elements.
It may be a bad connection, or a corroded wire, or some combination. It might be some other fault causing the wire to carry more load than it was designed for.
If you can trace it to a specific wire (as opposed to the terminals and/or connections at either end) then the preferred approach to replace it would be to remove the wire from the connector at each end and replace the whole wire. If you can prove there's a failure within the wire itself, for example due to external damage, then it's reasonable to cut out the damaged section and splice a replacement in. Make sure you route the replacement the same as the wire it's replacing, get the length right so it can't pull tight, add strain relief around the joint and re-loom/re-wrap as appropriate. Heat shrink self sealing colder/crimp connectors make it very easy to get a good joint protected from the elements.
you can't reliably measure wire resistance in the heavy gauge cable used for the alternator circuit with a typical multimeter. if there's a fault with the wires connecting the alt to battery then it's likely that you would see that visibly at a junction of the wire.
what you could do in this case with a typical multimeter is set it to measure volts and extend one of the probes from the meter so that one end can be prodded onto the alt output and the other end onto the battery + terminal, thus you are measuring the voltage between the alt output and the battery +. under these conditions you should see close to zero volts at all times if everything is ok. if the wring is good without any faults there will be a low volt drop when the alt is charging the battery (less than 0.5 volts) and anything above that indicates a voltage drop in the wiring
what you could do in this case with a typical multimeter is set it to measure volts and extend one of the probes from the meter so that one end can be prodded onto the alt output and the other end onto the battery + terminal, thus you are measuring the voltage between the alt output and the battery +. under these conditions you should see close to zero volts at all times if everything is ok. if the wring is good without any faults there will be a low volt drop when the alt is charging the battery (less than 0.5 volts) and anything above that indicates a voltage drop in the wiring
Tye Green said:
you can't reliably measure wire resistance in the heavy gauge cable used for the alternator circuit with a typical multimeter. if there's a fault with the wires connecting the alt to battery then it's likely that you would see that visibly at a junction of the wire.
what you could do in this case with a typical multimeter is set it to measure volts and extend one of the probes from the meter so that one end can be prodded onto the alt output and the other end onto the battery + terminal, thus you are measuring the voltage between the alt output and the battery +. under these conditions you should see close to zero volts at all times if everything is ok. if the wring is good without any faults there will be a low volt drop when the alt is charging the battery (less than 0.5 volts) and anything above that indicates a voltage drop in the wiring
edit: just read the OP's post again and see it's not the main output cable you're having a problem with as it's charging at13.6v ... duh..what you could do in this case with a typical multimeter is set it to measure volts and extend one of the probes from the meter so that one end can be prodded onto the alt output and the other end onto the battery + terminal, thus you are measuring the voltage between the alt output and the battery +. under these conditions you should see close to zero volts at all times if everything is ok. if the wring is good without any faults there will be a low volt drop when the alt is charging the battery (less than 0.5 volts) and anything above that indicates a voltage drop in the wiring
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