This LRO reader emailed LRO.email@example.com to ask David Long about wiring up an ammeter to his 1999 Land Rover Discovery 2 Td5.
I’d like to wire up an ammeter to my 1999 Discovery 2 Td5. I’ve been told by a few people not to do it: they say it upsets all sorts of electrical things; there may be a voltage drop between the battery and the alternator; and it could upset the voltage regulator in the alternator. There’s also a perceived fire hazard of having large 100-plus-amp cables running through the dash. Could a shunt not take care of this? Should I just stick with a voltmeter?
Clint Marquardt, Guildford, Surrey
What you’ve been told is in essence correct, though the idea of having a shunt near to the battery is a good idea if you propose to use an electronic ammeter. The cables to the dash with a remote shunt will be live but can be fused with no ill effects. The ammeter doesn’t go in the alternator output but carries all the loads in and out of the battery except the starter motor. Some of these cables may be at the battery and some at the starter solenoid, so extending and re-routing cables is on the cards. You could also void your insurance with such a modification.
One of the reasons they stopped fitting ammeters was the endless queue of worried owners (‘My ammeter shows 5A when I go at 40mph but my mate’s identical vehicle shows almost zero…’). Stick with the voltmeter. If it’s at 14.4v, all is well. Never rising to that value indicates a problem.
This workshop advice appeared in the March 2016 issue of LRO. Back issues are available to download on digital devices here.