A loadpro (sold on Amazon) is a very useful tool to help you here. It connects to a regular multimeter and acts as normal set of leads as well as it can apply a load (believe 250ma) to check integrity of entire circuit when loaded. Basically, it can really help with finding where the extra resistance in the circuit is. Just measuring resistance unloaded in a circuit will very likely mislead you. There’s ways to do voltage drop testing with a multimeter alone but it is more complicated. When dealing with these kind of issues here are my steps:
1. Check battery voltage loaded to ensure 12v. Making sure battery has some juice in it.
2. Disconnect connector of component with issue. Unloaded, check there is battery voltage. If there isn’t, you’re dealing with an open somewhere. Load the circuit and ensure there is still ~12v. Less than 500mv drop is probably ok; anything more means you have high resistance somewhere. Trace down the high resistance disconnecting and loading with loadpro to narrow down where the high resistance is. Don’t forget the ground. If all of these components share a ground I’d probably start there first. Good luck.
Optional would be to use back probes to not have to disturb connector but they’re not mandatory. There’s a chance the high resistance is within the connector and back probes can catch this without disturbing things.
Higher level optional is a Power Probe. Those things are golden but can be dangerous (i.e. fry an engine computer) if the user isn’t fully aware of what they’re doing. It’s basically a multimeter and a 5/12v power supply all in one. There’s other useful functions to it as well.
Last edited by Socalm3w; 18/01/26 02:00 AM.
