Head unit shuts down...

[Gene 5301]

I have an Alpine CDA9856 head unit installed in my 2000 Jeep Cherokee. Factory speakers in the doors. Polk MMC525's in the soundbar. All was well until yesterday...the head unit shuts down after approx 10 seconds. By shutting down, I mean no sound out of the front and rear speakers. The display works..the sub works...could a single blown speaker cause the head unit not to output sound? Thanks in advance.

[1996blackmax]

More information regarding your system would help us help you.

Do you have the regular speakers powered by the head unit's internal amplifier? If you do, try to see if any of the wiring that goes to your speakers is making contact to ground. Take a look at the area near your speakers first.

If you do not there might be some internal problem with the unit. Try resetting the unit to see if that fixes the problem.

How many speakers in total are being run by the HU, assuming the HU is powering your speakers?

[MacLeod]

Yeah, you need to do some more troubleshooting. If your sub works but speakers dont and youre using the pre-outs of your HU, turn the volmume down and switch the RCA's from the sub amp to the speaker amp and see if anything changes.

[Gene 5301]

The front and rear speakers are powered directly by the HU. There is a separate amp for the sub. Did more troubleshooting...
I replaced the HU with the factory radio..front speakers work..no rears..
I put back the Alpine HU and disconnected the rears..fronts do not work..
Tested Polk rears with home receiver...they work fine..
So, apparently there is a short in the harness going to the rears....

[MacLeod]

Try running a speaker wire directly from the hu to the speaker. If it works, then buy you some aftermarket speaker wires and run them instead of the crappy stock 40 guage wire.

[Kirk]

I recently installed an Alpine CDA-9847 head unit in my Mazda. Nothing worked, no sound, but I had power. So I called Crutchfield and the tech told me that the Alpine head units will go into protect mode if it detects a bad speaker in the system and shut down. I went out and disconnected the bad rear speaker and viola, all is working. I then replaced both rear speakers and the Alpine works flawlessly. So, disconnect the speakers till you find the bad short.

KIRK

[Gene 5301]

I found the short !!! I had a custom subwoofer encloser built that would fit into the cubby hole area in the rear of the jeep. When the enclosure was installed, the factory harness slipped from its location and became pinched between the enclosure and a sharp edge of the chassis. Over time, the vibration caused the insulation to wear away...

Next phase...install the MMc650's in the front doors.

Thanks for all the help.

[MacLeod]

Ive never heard of a HU going into protect mode! Thats good to know so I wont be tossing out a perfectly good HU someday! ;)

[1996blackmax]

Glad things worked out for you.