Well between my whacky work schedule and the rain and hot temps I just decided this morning to swap radios just to see if all the speakers work with the old Factory and they did so now I've got to test the radio without any speakers hooked to it to see if it still does the same thing. I hope its the radio.

Update: It was the radio that was bad. Returned the bad head unit. Just got the replacement yesterday so will be a few days before I can do the swap again.

Hate to hear that it was the HU for sure, but at least now you can get back to jammin'!

You may have to change how the speakers are wired. If you replaced the front speakers or the factory ones are 4 ohms, and the new 4x6's are 4 ohms, and the wiring is wired in parallel you're presenting a 2 ohm final load to the HU amplifier and they're not rated for that. It could be the cause for the failure on your stereo. They can get by with that from the factory because the tweeters use a capacitor as a -6dB crossover that limits their playing range to only high frequencies to protect the tweeter. It also helps to protect the amp in the factory HU since it doesn't see the tweeter as a load on anything but those frequencies the capacitor allows to play. Those are typically in a range not played well by the woofer and naturally slightly filtered, like the capacitor does for the low frequencies (it's measurable but not extremely audible in the case of the woofer) also -6dB, by the inductance of the woofers voice coil. So with the capacitor blocking lows from the tweeter, and the inductance of the woofer voice coil limiting the highs the amplifier is, in a sense, only seeing one speaker as far as it's load is concerned. That and it takes VERY little power to play high frequencies by comparison to that of low frequencies at the same output level.

I hope that all makes at least a little bit of sense. If the factory wiring is indeed connected in parallel (and I'm fairly sure it is) then you could very well be overloading the internal amp in the HU with the 2 ohm final load. If you put good aftermarket speakers in the front doors a good solution to your problem would be to pick up a small two channel amp to drive just the front door speakers.

Thanks Alton!!!!! That maybe what I end up doing anyway. I have a small 600 watt amp that I pulled out of my other truck because of a fuse failure. Thinking about wiring it for the door speakers and a 10" sub and that should solve that problem. maybe a little over kill but we shall see. I'm saving up for the sub now so I'm just gonna run the factory unit for a few more weeks. Then we shall see just how bad a butcher job I can do on this system.

Update: I still havent installed the Head unit I ordered new twitters that have a reducer so as to not over power the head unit. if everything shows up when its suppose to we will be jammin this weekend.

Alton your theory made sense.

After a Year and a half I still have not installed a amp or sub. Figure I'll let the new Owner put one in if he wants ( Promised my Cousins oldest son if he wants Blazer I'd sell it to him to drive back and forth to college). Alton's assessment was spot on about the tweeters. I installed RF tweeters with the factory Resistors and have not had any issues. The sound quality is superb. If I decided to put in an amp and sub it will be sometime this fall after archery season.