Ford stereo wiring help

"Pixel" (Improbcat) 04/04/2019 at 13:10 • Filed to: Project Colony Ship

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In my continuing quest to find a working radio for Project Colony Ship, i picked up an 89 lincoln radio , but it turn out the speaker connector is different.

Turns out the lincoln had an amp (missing from the junkyard one i got the radio from). On wiring diagrams the outputs are labeled as speaker signals rather than just as speaker wires. If i wire it directly to the existing speaker wiring will it work, or does it not output enough because it only feeds into an amp?

LOREM IPSUM > Pixel 04/04/2019 at 13:31

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It’s largely  going to come down to how many volts the head unit puts out. If it’s just outputting a low voltage line level signal it may not be enough power to drive the speakers. You may hook it up and find it works, but is very quiet, or depending on the resistance of the speakers it may not work at all. If the speaker resistance is lower than what the head units amp is capable of handling it may kill the amp in the head unit or otherwise drive it into protection.

Do you have a multimeter handy?

Pixel > LOREM IPSUM 04/04/2019 at 13:36

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I do have a meter . I know basic car electrical, but know nothing about stereo wiring and speakers.

jimz > Pixel 04/04/2019 at 13:38

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what’s the radio part number?  should be on a label in the format XXXX-YYYYYY-ZZ.

jimz > Pixel 04/04/2019 at 13:41

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for the most part, OEM systems with amplifiers still have the normal 4-channel amp in the radio, the external amp either boost up to higher power or is used to drive lower impedance speakers. I know here and there we’ve had radios with no internal amplifier for certain systems.

one thing that concerns me is if those are the only electrical connectors the radio has.  if so then the internal amp might be single ended and only about 7 watts/ch.

Pixel > jimz 04/04/2019 at 13:47

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E8LF-19B165-AB

Old radio is:

E7AF-18B865-AA

Pixel > jimz 04/04/2019 at 13:49

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There is a separate connector for power, etc. That one is the same and with it plugged in the “ new” radio turns on and seems to function . So this is just for speakers.

LOREM IPSUM > Pixel 04/04/2019 at 13:50

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If you’re able, locate a pair of speaker outs on the HU. Set bass, treble, and all faders to flat. Set the volume to roughly 80% of max and play some music, or a cd with test tones burned onto it . Set your meter to AC voltage and see what kind of numbers start registering on the meter. It’ll fluctuate, but try to get an idea of where it’s peaking.

While you’re there, locate a pair of speaker wires on the cars harness and check resistance, just so we know where we stand. I imagine it’ll be somewhere near 4 ohms, give or take, but 2 wouldn’t necessarily surprise m e either

CalzoneGolem > Pixel 04/04/2019 at 14:04

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Ford sucks at rad io s.

Pixel > CalzoneGolem 04/04/2019 at 14:05

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I do not disagree.

jimz > Pixel 04/04/2019 at 14:06

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crud, the drawing for the old radio doesn’t call out the pin assignments. My guess is it’ll work OK. my only concern is that the drawing for the old radio says two of the outputs are 6 watts RMS, which makes me think those are a single-ended amplifier. If the speakers all have two wires (+ and -) each going to the radio then it should work. if there are fewer (-) wires than (+) ones, then one or more channels ties the (-) to ground and the radio will detect that as a short circuit. 

CalzoneGolem > Pixel 04/04/2019 at 14:09

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In order to swap my stereo in my Taurus to a single din. I needed to dismantle the hvac controls and swap them into a new face plate then run a wiring loom to the trunk!

The stereo in the Forester was already double din size and I could take it out with a screwdriver and a $ 10 kit to put it all back in.

Pixel > LOREM IPSUM 04/04/2019 at 15:14

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Did some testing, it got weird. Here is what i found.

The speaker wire connecter in the dash has 2 sets that test at ~4.5ohms and 2 at 8ohms.

The speakers out of the lincoln (which i also picked up) test at 4.8 oms front (test after capacitor on speaker) and 5.3 ohms rear.

The old radio outputs ~ 5.5 volts on the two outputs that tested at 4.5ohms and 0 on the two that tested at 8ohms (though fade/balance could be messed up).

The new radio tests at 0 volts across any combination of pins, but tests at 4.98 from the metal around the connector port to any of the 8 pins.

ranwhenparked > Pixel 04/04/2019 at 16:06

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Heh, I have a closet shelf full of those, because that's how many I had to go through to find one that worked well and fit my Town Car.

LOREM IPSUM > Pixel 04/05/2019 at 01:03

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Sorry for the late reply. Today took a hard turn on me.

Best I can tell, the old HU appears to be putting out around 7.5 watts at that volume with a 4ohm load and presumably around 3.8 watts at 8 ohms. I’d imagine the OE speakers are very sensitive if they were being powered directly by that head unit.

The Lincoln HU however, I find a bit baffling. If we were to assume that 4.98 volts was the output voltage for each channel there might be a shot you could just connect the speakers an d it would work, albeit possibly a bit quieter than before, but clearly the power isn’t coming from where we were expecting it to . I have no idea how Ford cobbled this together, but t hat 4.98 volts could actually be the remote turn on lead for the lincolns external amp and not an audio signal at all. If that’s the case, it may be possible the lincoln HU is outputting either very low voltage on those other leads and thus not suitable for a di rect speaker connection , or it may in fact be broken... or it may be working ju st fine but it’s just unfamiliar to me . Honestly , I’m not sure.

Jim seemed quite knowledgeable about the oe stuff so hopefully he can shed some more light on it. If not though, I suggest registering on www.diymobileaudio.com and asking over there. There is more collective car audio and speaker knowledge there than anywhere else I know of. Hopefully someone  has dealt with the fomoco stuff enough to help.