I found the reason after looking around. Some speakers say 4ohm but are really 2~3 ohm which makes the HU amp go crazy. Which would make them sound louder cause they are less restrictive.

Most highier priced HU's can take the differance and not shut down, But some can't. The only fix is is to add a 4 ohm resistor to the speakers or add a Amp. I find it still strange that some HU's use a 8ohm coil to run a pair a speakers. As some will have four 4 ohm coils for each speaker. If the coil is not stable under 8ohms then it will over heat.

 

I would think that a HU should be able to run the speakers, but last night I played my stereo a while last night and after it cut out, I felt the front of the faceplate and almost burnt my hand. It was HOT!! I think the HU is getting over loaded.

 

Most speakers are pretty accurate in terms of their impedance rating these days. They should be pretty close to 4 ohms impedance, with slightly less DC resistance (closer to 3 or 3.5 ohms). HUs amplifiers are a little tricky in that they can't dissipate heat as well as an external amp. HU amps live in an environment with a bunch of other electronics that are already generating heat and the whole unit being mounted in the dash can significantly limit air flow. Thus, when pushed to higher output levels, thermal protection can kick in and shut the unit down.

If you're only running your unit for 5 or 10 seconds and then it shuts down, it is suggestive that you're taxing the power supply in the HU to drive the speakers. Without sufficient power, the unit shuts down. That can be a function of too low impedance on the load, or just a design limitation of the unit (driving the unit to clipping). HUs are sensitive to power availability as their is a lot of microprocessor functionality in units now that require stable power.

Adding a 4 ohm resistor wouldn't be any better than just turning the volume down. The 4 ohm resistor would drop approx. half the wattage across itself, dropping the volume in half (probably a little more than half, since it's a purely resistive load and the DC resistance of the speaker is less than 4 ohms). Plus, the resistor would have to be of sufficient wattage rating to handle the current being dropped across it. You'd still be drawing the same power from the HU and getting less volume. So, if you're already taxing it's power supply, the problem wouldn't go away unless it truly a load problem.

I would just drop the volume level down until you can get an external amp installed. There are other alternatives, such as a fan in the dash to move air over the HU, wiring additional speakers in parallel, etc., but nothing will be as satisfying as an external amp.

PS - it does seem odd that the word "ohm" doesn't appear anywhere in the owners manual for this unit.

 

The factories are real thight about that. I think there playing games with us.

 

did you try this with your truck off? maybe if you turn it on the alternator will give you the extra voltage you need.

 

Sorry, I don't understand what you're saying... This all happens when I'm driving down the road. Or in a parking lot with my truck on.

 

An HU definitely isn't going to tax a battery that's capable of starting the vehicle. The power supply that's being taxed and depleted is the one inside the head unit that performs the DC to DC conversion of the power supplied by the battery, due to the excessive current flow to the speakers that it cannot sustain (possibly due to an impedance issue) or the heat generated by the amp as this volume is sufficient to overheat the unit. If it only happens with a few seconds of operating at the higher volume, then it's not a heat issue.

 

Thanks for all your help, this may sound stupid but my whole problem was because i messed up two connections and did not think of checking them.

And Romer b2 could it be a short in the speaker or near the speaker that somthing is grounding out.

 

I've checked and rechecked connections making sure nothing was grounded, but it never hurts to do it again.

 

LOL I did the same thing and it still ended up being a connection. IDK how you did your connections but i used the heat shrink connectors and must have let the wire slip while it was still hot. They are unnoticable but can wiggle enough to cause trouble.

Also check the case of the face, there could be somthing causing a ground loop inside the dash.

 

What do you mean something might be causing a ground loop inside the dash? What would be touching the casing?

BTW I twisted all of my connections then used electrical tape, then put a cap ontop of them.

 

If your suspect a ground loop, Run all connections to one point and make sure its grounded to frame.

 

When i installed mine there was the braket in the back but that does not provide a ground at all, cuz i checked it.

 

Well today my head unit started cutting out a lot, and when I turned it up at all, it was really weird sounding, so I checked all connections and everything, everything was still good. I think my speakers just crapped out on me, because it sounds like they've blown.. so basically I took out all my speakers and tore them up. I feel better now. But now.. I have to put in new speakers, so I'm going to buy my entire system before I even install it this time. I'm starting from scratch.