# The curious case of the 4WD



## Mort (Nov 26, 2008)

Sounds like a bad ground, would explain a weird speedo.


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## de-nagorg (Feb 23, 2014)

I just have to say it.

Loose nut behind the wheel! :devil3:

As stated by Mort: possibly a ground issue, You probably bumped something in / under the dash when you were changing the radio, as well as your big hands hit the shift controls . 

Don't get insulted, I have the same problem with my Gorilla Paws. 

If it does it again look for a loosened ground on the controls somewhere.


ED


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## Bigplanz (Apr 10, 2009)

A short vid pulling the radio at the salvage yard. Took all of 5 seconds. Little U shaped tools cost about $5 at any autoparts store. If you look close, you can see the AWD/4H/4L selector knob at the lower left, below the radio.


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## ukrkoz (Dec 31, 2010)

I had brake lights fried by new stereo - TWICE - in my Taurus. I had stereo replaced with a new unit, same brand - it did it again. I replaced it with a different brand - and it went all fine.
I have only one word for this - Ford. 
WDF has stereo to do with brake lights and why particular brand was frying them and the other not - only Ford knows.


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## Bigplanz (Apr 10, 2009)

ukrkoz said:


> I had brake lights fried by new stereo - TWICE - in my Taurus. I had stereo replaced with a new unit, same brand - it did it again. I replaced it with a different brand - and it went all fine.
> I have only one word for this - Ford.
> WDF has stereo to do with brake lights and why particular brand was frying them and the other not - only Ford knows.


How strange. Brake lights shouldn't be affected by a radio, of course. In my instance, I suspect that when I pushed the new unit in, I somehow jiggled, kinked or squeezed the wiring harness, which contains wiring for the AWD switch. I have no memory of changing the switch from AWD to 4H, but I must have done that two. When 4H or 4L are selected on the switch, there is a little light that comes on, on the dash. This light was not on, even though 4H was selected. I drove around, right after the radio install, speedo was showing me going 80, car was shifting bad, lagging, surging, etc.

I stopped, played with the switch for a minute. Went inside, cooled off (I was mad, of course), went back outside, started it, switched to 4L, drove maybe 50 feet, switched it to 4H and the light came on. Drove a half a block, switched it to AWD and it has been normal since then. Has to be some sort of jiggly connection, ground wire, intermittent short somewhere in the harness. If it happens again, I am going to need a better wiring diagram than this Haynes manual. 

BTW, junkyard radio, $20. Works perfectly, radio, CD, etc. A direct swap with the one originally in the car.


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## Brainbucket (Mar 30, 2015)

As long as it is doing ok now and just screwed up that 1 time, you probably hit the switch(s) but not all the way down so maybe it was getting crossed signals or both signals. I wouldn't worry about it unless it happens again.:vs_cool:


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## ukrkoz (Dec 31, 2010)

I hd 99 Silverado and about 1000 miles after I bought, used, switch started acting up. I actually drove for about a year with toothpick jammed between a button and switch case to make it work, then got tired of it falling out all the time, and replaced the switch.
Yes, it should not affect the brake lights - the stereo - but it did. And for some reason one brand did it twice - they replaced stereo under warranty, then they wanted to replace it 3rd time and I said - no, different one - and it was all good thereafter.
Ford is very weird electrically.


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