Head Unit or wiring?

[landtank]

I looked at the EWD and it would appear that the Head unit does turn on the amps, but why would you want those things hanging off the side of your speeker line. They can't do any good only harm.

And I'm smart enough to know that I'm not smart enough to know what the implications of leaving them in are, so I pulled them out.

 

[trucruiser]

Another possibility is you may have blown the front speaker and when it gets to higher volumes it causes the voice coil to ground out slightly, which could be causing your priblems also. just a thought.

 

[ParadiseCruiser]

Eric -

Thanks for your post. My first reaction was, "hey.. good catch." I have made my share of mistakes... but logical or not, my remarks on this one are fundamentally correct... and so are Rick's. Let me clairify the error I did make, and add the history.

This all came up here over a year ago, and several of the others went over this same ground. I had my doubts about the external amp being an issue, but like Rick would rather err on the side of safety. Anyway, here are the facts:

1. When the ignition is at "Acc" or "On," there is 12v+ on pin 1 of S11 which is plugged into the external amp. This is true whether you are using the large, white R2 connector (ext amp); or the two smaller, gray R1 & R3 connectors (int amp).... because this 12v+ feed is independent of these connectors. This is some type of idling voltage, but apparently not driving the outputs*

2. When the OEM head unit is powered up through R2, the B+ voltage that powers the output transistors of the external amp* appears on pin 1 of S12 which is also plugged into the OEM ext amp. When you power up an aftermarket head unit plugged into R1 & R3, you are not bypassing the OEM amp, but just feeding it from another source (R2, and R1 & R3 have a common junction at I14). So, the B+ voltage still appears on pin 1 of S12.

* I'm making some educated guesses here because the OEM ext amp is a "black box" and without schematics, there is no way to be absolutely certain.

And because I originally believed Eric's take on this, and not the confusing schematics, I got in there with my meter and measured the d**m thing using both configurations. Folks, that OEM ext amp is powered up and running either way you slice it.

And like Rick, I believe that having even an idling audio output - or even speakers - tied to the system creates a potential for the kinds of problems that these threads are often all about.

Solution: Pull the glove box (two screws), and pull the two connectors out of the amp and tape them off. NOW the amp has been bypassed.

Cheers, R -

 

[ginericLC]

Ron,

This is good info. Basically it is functioning like a normal car amp then. There is a positive running to the amp all the time. When the radio is turned on it turns on a switch inside the amp and lets the current flow through the amp. If the radio is never turned on the circuit is never completed and it sits idle. When you were testing it you were completing the circuit. With this said I still think there is no harm in it being left hooked up, but just the same I'm going to go about removing it. I'll probably take all of the excess harnesses out at the same time. Thanks for researching for us.

Eric V.

I wonder if mine is being fed (turned on) at all really though as I never hooked up the blue wire to the back of my new radio.

 

[ParadiseCruiser]

E -

>> With this said I still think there is no harm in it being left hooked up...

Yep, I agree. There is no proof positive that it would create a problem... but I believe the circuitry in the aftermarket head unit would dictate how sensitive it might be to an idling amp, or even the imbalance of the speaker wires sitting on the outputs of the ext amp, idling or not.

When Phil [PPC] brought this up long ago - first alerting me to this issue - he, like Rick, chose to err on the side of safety and I still think that is good advice.

>> I'll probably take all of the excess harnesses out at the same time...

Ha! Now that might prove to be more difficult than all that has come before

Good luck !

R -

 

[landtank]

I can't see taking out the extra harnesses of or even taping up the empty connectors. The wiring loom is setup for other factory systems even though we didn't see them here in the US. In tose trucks the wires are just unused and hanging out.