Ive been dealing with this for awhile but havent been able to solve it. The head unit in my car get super hot in the back where the heat sink is. This happens even when the key is out of the ignition. I have unhooked both front speakers, even cut the speaker wires just after the head unit plug to rule them out. The only wires still connected to the unit are ground, ACC main power, constant power, light on, and antenna power. I also tried two different head units , same problem. The ground wire on the passenger side of the dash frame is tight. How can I go about testing these wires to see what is going on? I have installed several systems, made boxes, etc but I am still a noob with a multimeter. I think there must be a short somewhere in one of these wires. Took it to a stereo shop, werent much help just wanted to sell me a whole new system.

 

That does sound odd, have you had a look behind the head unit to see what cables are running behind there? Any of the wiring loom behind there getting hot too when the head unit is out? I DJ'ed a few years ago and found when my amplifier got too hot (full volume) the sound would cut out and I would need to turn it down. Head units actually have a small built in amplifier.... usually putting about 4 x 50W outputs and maybe a subwoofer output too. However, you could almost rule out the headunit amplifier, what you might want to do is start tracing the wires for the speakers. If speaker wires are touching the metal on the body anywhere it will put strain on the headunit. My best suggestion is plug the headunit back in, then unplug the speakers and plug them in 1 by 1 slowly and see if it heats up again or not! I'm terrible with a multimeter too haha. Best of luck, let me know how you get on!

 

thats what I originally thought. but now i have the head unit plugged in with no speaker wires hooked up at all. i cut them from where the go into the head unit. so it has to be one of the power wires with the problem

 

Hmm well next thing I can say is make sure it has a good ground!! With current running through the ground cable, the grounding points on the chassis inevitably corrode. Unscrew the grounding point, get a wire brush, rub the grounding point down and apply grease. Silicon grease, or similar. If you have a spare 12V battery laying about (or access to another car) then try bypassing the Honda wiring and run a power cable directly to the other 12V battery. Make sure to obviously keep the ground connected. You will need to refer to your head units manual for wire color diagrams. Doing this will bypass all the Honda wiring and you will be able to narrow it down easier. If it is the Honda wiring, I hate to say it could be any number of things, ignition wire, air-con wiring, alarm etc. I wouldn't be any use there!