Discussion and questions related to the course Motorsport Wiring Fundamentals
I am calculating current draw so I can size wires for my harness. I came across a VVTI solenoid on my 2jz and measured a resistance of 6.5 ohms.
I = V/R
I = 14/6.5
I = ~2.15A
Therefore 22awg wire would be appropriate. Is this the correct procedure for measuring solenoid current? Not sure if there are any special considerations such as when measuring coil currents. Also, for sensors with 3+ pins (TPS, fuel/oil pressure, flex fuel) what is the procedure for finding these resistances? Do I just put multimeter leads on their power/ground pins and use the resistance given? Or should I be putting one of the leads on the signal wire? Thanks in advance
While measuring the resistance works for resistive load (like most TPS sensors), for inductive loads (like your VVT Solenoid), the current required is usually determined using a current probe (or the vendor data sheets).
Bottom line -- all of your engine sensors will draw in the 10's of mA range, so you can use 22 awg for each of them. I may use 20 awg for Solenoids, Injectors and perhaps Coil-on plug triggers (generally like 18 awg for COP power/grounds where the real current is transferred).
Great, thank you. That makes it easy.