Car Stereos: car stereo problems in my 01 grand cherokee, rca cables, digital multimeter

Question
hello good day,

here is the scenario, months ago i wanted to upgrade the HU in my GC but couldnt becuase of the PCI Bus cable on the back of the stock HU. forward to now. i have added an amp and subs to my stock HU (havent heard them sound yet) my question, i bought a lineout converter and installed it in my jeep, now i assume everything is correctly wired up (to the rear speakers). but i dont have any sound coming to the subs. there is power to the amp becuase the amp power's on. is there any way i can check to see if everything is working correctly on the line out converter? could i have a defective amp even if it turns on? this is all frustrating all i want is some bass in my car thats it...your help will greatly be appreciated thank you in advance for your help

Answer
Hi,

I have to say, I've never had a problem with replacing the factory radio in a 2001 Grand Cherokee.  The PCI bus wire is present in quite a few different Chrysler vehicles; generally it can just be unplugged and left disconnected without any issues.

Unfortunately, it's hard to say what's causing the problem with your subwoofer system.  If I were troubleshooting this, I'd probably use a digital multimeter with an AC voltage function to find the break in the signal chain.  Start by disconnecting the subwoofer wires from the amplifier, and measure the AC voltage at the amplifier's speaker terminals while the system is playing.  If there's an audio signal present, you should see a varying AC voltage on the meter, that increases as the volume goes up.  

If you're finding voltage on the speaker terminals without the subs connected, but don't hear any sound when you connect the subs, then there may be a problem with the subwoofers or sub wiring.  If there's no voltage present, though, then you can go back and look for voltage on the center pins of the RCA cables coming from the line output converter.  An amplifier that has voltage on the inputs, but no voltage on the outputs, may be defective.

Where are you connecting the line output converter?  In these vehicles, I usually like to connect to the output at the factory amplifier (if equipped), rather than to the output wiring behind the radio.  (Most Grand Cherokees are equipped with a factory amplifier, located under the rear seat).

Hope this helps!

Brian