new head unit getting really hot

[roundeye69]

I just installed a pioneer head unit in my 84 mazda, I used a wiring harness and when I turned it on it worked fine for 2 -3 minutes then I lost sound and the head unit got really hot, I unplugged the harness from the stereo and noticed the fuse on the back had blown, im not sure what the problem is, I've installed numerous car stereos with no problems.

 

[firechief]

We need more information on the head unit and the amp. Model #'s. It could be that the amp was dumping power into too low of an impeadance, working really hard, but it has protection circutry that activated the way it was supposed too. If there was a direct short, say on the speakers you would not have heard anything, and the fuse would have blown right away.

 

[roundeye69]

Its a pioneer deh-3200ub, I don't have an amp.

 

[Perry Babin]

With the harness unplugged from the head unit and the black meter probe on a known good ground, confirm that you read infinite resistance (OL for most meters) on every speaker wire that's connected to a speaker wire in the vehicle.

 

[roundeye69]

The negative wire on the speaker the numbers on the meter continuously count up but the postive side on the speaker stays at one on the meter.

 

[Perry Babin]

What's the resistance measured directly across the speaker terminals (in the wiring harness) for the channels with speakers connected?

 

[roundeye69]

At the harness they read infinite resistance, except the rear speakers but they weren't working when I had the head unit on, so I disconnected them. (There's a factory amp for the rear speakers I didn't unhook, and was told wouldn't work with the aftermarket headunit anyway.)

 

[Perry Babin]

Did you have the head unit AND the factory amp connected to the rear speakers?

 

[roundeye69]

I didn't unplug anything from the amp, but am not sure if its hooked up, there was a weird white cable hooked to the factory radio but isn't hooked up now. Not sure if that was for the amp or not.

 

[Perry Babin]

Did you run new wires directly from the head unit to the speakers?

 

[roundeye69]

No, do you think the speakers are the problem? I can run new wires to the speakers and see if that makes a difference.

 

[Perry Babin]

I think you may have permanently damaged the head unit's internal amp. Disconnect the speakers wires for the head unit's harness from the vehicle and cut the bare wire from the speaker wires.

Install a 5 amp fuse in the head unit and apply power. Does it blow the fuse?

If not, do you read approximately 1/2 of the battery voltage on all 8 speaker wires coming from the head unit? They should all be essentially the same voltage.