Thread: Accessory power feeds in new cars

Hi all


Today I had a good customer rock up with a 2010 Toyota Prado today complying that the Phone kit would no turn on some times and the radio/cd would not make any sound at times, So think phone module is at fault and causing the radio to mute. I located the phone module and test the mute wire with a test light, no mute, then probe B+ and ACC for the car kit to find a good B+ and a weak ACC, now a 15/20 min job just got a lot longer now with the customer is getting worried as the radio is out, console apart, under dash/kick trim drivers side out to trace the power for car kit.

I found the power for the phone kit attached to the speaker positive along with acc for a two way radio and acc for a in car pc that provides emergency job data and navigation info to the speaker negative wires in the kick trim.

Rewired to the ACC socket that Toyota fitted and all is good.

I have seen this problem before when installers relied on led test lights and don’t check with a multimeter or a low wattage test light and would seen the low voltage to the acc feeds (a speaker lead in a oem head unit or after market unit would read approx 6 volt) a led test light won’t show the difference as I showed the customer, and a lot of new automotive equipment will turn on some times with 6 to 7 volt as a acc feed.

Installers need to take more care with where they tap into for their power feeds.

Sorry for my ranting, just thinking in this day and age we should check where we get power for accessories in today’s cars, tap into the wrong wire and blowup a airbag or worse cause a SRS system not to deploy then some one would be in deep poo poo.


SS Dave