Headunit turns ON/OFF while driving??? - PeachParts Mercedes-Benz Forum

Peyton300TD · #1 10-14-2003, 03:14 PM

Hey there. I have a JVC KD-SH55 headunit that i recently installed. With the engine off the headunit stays on just fine. However, when i start driving it goes ON/OFF very frequently. After a while it stays on more consistently.

I am CLUELESS as to why this is happening. Any ideas?

-when i wired it into the car i soldered all the connections and wrapped with electrical tape- the connections should be fine.

Eric

Benz300 · #2 10-14-2003, 05:22 PM

Seems like when the car is on, the power to the unit is being interrrupted. I suggest putting a voltmeter to the positive and negative inputs of the unit and start the car while at stand still. and leave the engine running, when the unit turns off/on see if the voltage drops or cuts off. if that's the case then you need to find out what's causing the voltage fluctuation.
good luck.
P.S. make sure you monitor all three, the negative terminal, the constant 12 volts, and then the acc 12 volts (the line that has power only after you turn your key on).

Peyton300TD · #3 10-14-2003, 09:50 PM

you're right!!! i realized today when driving, that i could have the volume at a higher level when i was on the highway, and it had to be low at a stop light. otherwise it would turn off again.

it's almost like it isn't getting enough power to run. thanks for your advice

eric

speedy300Dturbo · #4 10-15-2003, 01:38 AM

Hey Eric,

I recommend crimping the wires vs. soldering - it's easier, less smelly, and works just as well. Hopefully you don't have a problem with the radio's internals. To check, pull the stereo and wire up a dome light bulb with end of the bulb going to ground and one going to the power wire that the stereo is hooked up to. Tape it somewhere so you don't have to look down at it while you're driving

Go on a bumpy road. If the bulb flickers on and off in the same manner that the stereo does, check the wiring again, and maybe splice into the positive lead for the cigarette lighter. That's a pretty solid source of power.

#5 10-15-2003, 08:29 AM

Mine did the same thing until the alternator finally died, I replaced it with a new one that was from a s500 which has a 143amp alternator. the stock is only 60amp. It was a easy swap, only took about 1-1.5 hours

Peyton300TD · #6 10-15-2003, 01:41 PM

wow, i think you're right. my mechanic is having me test my voltage fluctuations and see what's going on. he said that my alternator is 70amp and should be enough. also said the new cars only have 120amp with all the computers they have in them and that's plenty. he's skeptical its the power of the alternator.

thanks for your tips

eric

Benz300 · #7 10-16-2003, 12:29 AM

Eric,
I would suggest that you check your wiring again. Looks like you should use an alternate input for your 12v power input for your unit.
Best thing obviously is get a new line straight from the battery with an inline fuse for constant connection, and then the other from any of the other lines that turns on when you turn the key.
as an intermediate test, try this :
connect both your lines, constant 12v and acc 12v to the constant 12volt connection of your car. just make sure to power off your headunit when you turn off the car since it wont power itself off in this scenerio. see if that works fine for you. if that's the case then it's the acc 12v connection of the car that has the problem. if the problem persists, then switch both headunit 12v inputs to the acc12v connection of the car.
this way you can eliminate which ones of the 12v wires in the car is having problems.
good luck.