Does anyone know what the two plugs on the back of my factory stereo go to. One is a large rectangular plug and the other is a smaller square plug. A tech at a local road shop told me the small plug goes to nothing? Please Help!

99 F150 reg cab sh bed

 

Small plug is for the radio, the big plug is for the amplifier. My new radio didn't use the amplifier plug. good luck.

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01 supercrew,4x2,all black,5.4,captains chairs,355 ltd slip,trailer tow grp,remote keyless entry.
(MODS)gibson supertruck,K&N generation II air intake,expy console,lund intercepter,A.R.E LSII hard tonneau,tinted windows,E&G classics mesh speed grill,mud gaurds,ford seat covers, bed liner,ventvisor's,westin chrome nerf bars,smittybuilt outland sport bumper guard,KC highlights, Hella fogs, Jensen flip down 6.8 TV, santeca 4" TV in passenger sunvisor,DVD player,panosonic cdqf800 fm-cd,pioneer 6865 speakers.

 

I have been told the same thing by two installation websites, Crutchfield, and a friend at a stereo shop. I don't buy it. I know the bigger plug is the power and speaker outputs because I have that harness from Crutchfield as I am installing a new head unit as we speak.

I think the small plug has something to do with the speedometer or the computer or else how would it know when I slow down? I do not buy into the theory that Ford put it there for nothing. They are too cheap, it would not be there unless it did something.

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SumterGator
http://sumtergator.f150online.com
Let the Big Gator Growl

 

After some digging I have found the same answer, the big plug is power and speaker. Does anyone have a clue to what the small plug is? Speed control is possibe but it has to run more?

Thanks

 

its for the cd changer isn't it?

 

Someone has suggested that it goes to a cd changer, but since I dont have one, would it still be there?

Thanks

 

I dont have a changer nor does my CD player have changer controllers. I cannot see Ford installing a wire for that. I would think it would have to be to the speedometer or computer.

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SumterGator
http://sumtergator.f150online.com
Let the Big Gator Growl

 

Hey guys, I work in a truck factory building what use to be Ford's class 8 trucks. We install the same radios in our rigs as are in my 2000 F-150 and you guys are right about the large plug being power and speakers, and the little plug is part of the amp and cd controls. As for it being in some trucks and not being used, well for all of you guys who think Ford is cheap they are but all the electrical harnesses are generic and it saves money only having one harness with every option on it then to have 10 or more seperate harnesses. Plus it saves up valueble shop space for stocking it at the factories. So for those of you who have a base stereo and want to upgrade and the dealership says it'll cost you an arm and leg. Just go to the wreckers and see if they have any late model F-150's with the stereo's still in tack then you can do it yourself.

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Kiki

 

It's for the CD. It's cheaper to install it in all of them than to have specific harnesses for each radio. Example, my Mustang coupe has a convertible top wiring harness under the console. And all of the new radios have the amp in the head unit.

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2000 F150 XLT 4x4 Short Bed. Amazon Green, 5.4L, SuperCab, ORP, Tow Package, Sliding Rear Window, Electronic Shift, Keyless Entry, LT265-70-17 Tires, Clarion Pro Audio, Herculiner Bedliner, Air Silencer Removed.

1994 SVT Mustang Cobra. #1032 of 6009. Black coupe with black leather int., 3.73 rear, Bassani Exhaust, Aluminum D/S, Bridgestone RE-71 255-45-ZR17

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Ok then what are the two covered openings on the back of the stereo for? That are plastic and resemble the other two as if there is an identical stereo with two other plugs such as for the amp and the cd changer.

I looked at the wiring diagram in my Haynes manual and they do not go to the changer...incorrect colors and number of wires.

Where do you think the radio gets your speed data so it can turn down the radio when you slow down? Three of those wires that are together in a seperate area in the plug in question match the three in my wiring guide for the speed control. I will plug in my meter while driving to test this theory.

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SumterGator
http://sumtergator.f150online.com
Let the Big Gator Growl

 

Why not jsut get an wiring harness and forget about the other plug? Do you want to put in a factory changer or something?

 

Hey Gator...

Could you let me know what you find out with that wire voltage vs. driving speed??... That would be a terrific place for me to tap off of the truck electrical to get the speed so I can build a trip computer for my XLT. Thanks

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2001 F150 SuperCab XLT
4x4 Off Road Package
5.4L V.8 3.55LS
Pioneer Premier DEH-P410
A/D/S/ 236is
Alpine SWR1040 Subwoofer
Rockford Fosgate 500.2 & 400.4 Amps

 

Speed sensor is definately a part of that plug. I haven't been able to figure out the rest. I am guessing it's either for the changer option, or amp. I don't use it with my replacement Clarion deck, so can confirm it's not really necessary for anything.

 

In some Ford vehicles the plugs you are talking about are for the Premium Sound System that Ford uses. I have done several installs on cars with these and they are a pain to bypass. More than likely if you have one of these systems you have a factory amp in the truck somewhere. You can buy a harness for these systems that will allow you to put an aftermarket head unit in the truck. You local Best Buy or car audio dealer should have them, get Metra if possible. Hope this sheds some light on the matter.

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98 F150 XLT
4.2 V6/5 Speed Trans.

Mods and Upgrades

Pioneer FHP8800 HU
Pioneer TSA6895 Compression horn 6x8's
Pioneer TSA6865
GMX542
MTX Stealth Box w/ 2 8in. subs... mild bass
Compustar SHF-2W-AS
alarm/remote start
Clear corners
Xtang soft cover
Airaid Intake System
Switched the 16 in. XLT
wheels for the 17 in' ORP's
35% Window Tint
Weather Tek Window Visors

 

Your harness will only connect to one of the plugs on the factory HU. The other one is a square plug which your harness will not fit because it is not used.

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99 F150 Reg Cab Short Bed 4.6L
Dual Cat Back W/0 Mufflers
K&N Filter