pac ms frd1 and 4 channel amp

Pac-Audio.com has been in business since before 1985.  That is when I first learned of this company.  They made line out converters.  This was so long ago that the model number was SNI-8.  That is a line out converter for an 8 watt per channel radio.   Shortly after that time, high power radios became more and more frequent.  They had to add the SNI-15 to their lineup.  That is for a 15 watt per channel radio.  Point being, they know people install amplifiers into their vehicles. 

In January this year we installed a Double Din DVD player into a 2011 F-150 with the Sync system.  This piece worked flawlessly.   Customer came in yesterday wanting to install a 4 channel amp and upgrade his door speakers.  The installer is giving me trouble telling me that the module is not going to work with an amplifier.  My argument was, dude, they have been making LOCs for over 25 years, they know people are putting amps in their cars. The module will handle the power of an amp.  Guess who the idiot was.  Yup it was me.  We did get it in and working.  Took some work, but we made it happen.  Pac tech support was freaking out when I told them we ran an amp on the unit, 

All was fine at low to medium volume.  Problem was at high volume with all 4 channels driven, the module would power the radio down.  That is how it kills rear speakers to answer a bluetooth call.  2 channels at a time would work much better, amp had to reach clipping before unit would shut down.  Thought this was going to be an easy fix, bypass the box with the rear speakers.  Front has to run through it in order for the bluetooth to work.  That did not help much.  My customers Love them some clipping.  It was still shutting down.

Pac tech support did tell me about the brown loop.  If you cut that loop, and connect the radio's mute wire to the brown loop wire that is closest to the end of the plug, this will mute the radio instead of killing power.  It would mute the radio when the volume was turned up, this was much better than having the deck power down and have to wait for it to come back up. 

What was done to fix the problem:  I had to use a transistor and 2 DPDT relays from Radio Shack to completely bypass the module with all amp wiring.  I will post diagram for the transistor.  Transistor is triggered by the brown wire of the pac module.  Same wire that mutes the deck.

Relays wired as follows:  Common terminals to speaker wires.  Only front channels need to go through relays.  Rear channels can not go through the module, just wire the rear speakers directly to the amplifier.

Normally closed contacts to the output of the amplifier.

Normally open contacts to the output of the module.  This is only needed for bluetooth phone operation.

So don't go thinking that Pac knows you are going to amplify your systen, and make their interface modules accordingly.  If you think that you may look like you have no clue.  Like me.

If using Bosch/Now Tyco relays.  30 is the common terminal.  this connection goes to the speakers.  87A is the normally closed connection, this is to be connected to the aftermarket amplifier.  87 is the normally open connection, this connects to the output wires of the above mentioned Pac integration harness.

If using these relays, it will take a total of 4 relays.  2 for the left speaker and 2 for the right speaker.  One relay for the positive wire, and one for the negative wire. 

If you do use a DPDT relay, post a picture of the connetions of that relay and I can give more guidance.

I did not get a layout of the relay from Radio Shack.  They did have a picture, from what I could see through the smoked plexiglass cover, this should be accurate.  Check against this info before wiring it up.  Top set of contacts should be the NC (Normally Closed) contacts.  Just below that is the NO contacts.  Then the Common contacts.  Coil connections are at the bottom of the relay.

I forgot to draw the diode on the diagram.  It needs to go across the coil of one of the relays.  The end of the diode that has the band on it MUST be connected to the terminal that has positive voltage.  The transistor does not need a heat sink.  The tab of the transistor is connected to the middle leg.  There is ground on the tab.  If you want to mount it to a bracket or directly to the chassis, that will be fine. 

I looked at the pictures you sent.  The above diagrams are exactly what you need. 

Did you buy the exact part number relay I suggested?  They sell a 3 amp and a 10 amp device.   The pic looks like it may be smaller in size than the ones I have used.  if it is the 3 amp unit, I have no idea how long it will last.

You have the correct relays. 

How big of an amplifier are you using?    If it is under 200 watts per channel, you will never hear the benefits of upgrading your speaker wire.   

Place a couple ty-wraps an inch or so below the end of the heat shrink of the transistor.  Tighten them enough to keep the wires from twisting.  The legs of the transistor do not like being flexed.

I finally got around to correcting the picture.  I am glad you caught the mistake before you built it.  The picture was labeled wrong.  Verbal instructions were accurate.  I would love for a moderator to delete this post and replace the earlier pic with this one.  Thanks in advance.

https://www.the12volt.com/relays/page5.asp

On the above page there are several diagrams with a quenching diode paralleled across the coil of a relay.  A diode is a polarity sensitive device.  You need to put it across only one of the relays.

Use the last diagram I posted for the relays.  The other guy pointed out that I had the 2 inputs reversed in the first diagram. 

I will read your long post later today and then answer any questions you have.

The relays are the only way to do what you need done.  A diode will not isolate the amp signal from the sync module.  A diode in line with an audio signal will not sound good at all. 

I too was shocked when PAC tech support told me that I could not run an amp through their module.  The very first piece of PAC equipment I ever saw was an SNi-8.  A line out converter for an 8 watt radio.  They got their start interfacing OEM radios to aftermarket amplifiers.  Why would they make a piece as this that would not allow you to use an amplifier?