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Car Forum / Ford / Ford Trucks / March 2008

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'93 F-150, third brake light?

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Nate Nagel - 25 Feb 2008 00:51 GMT
Just picked up a fiberglass cap off craigslist for my '93, I'm happy
because they seem to be hard to find for shortbeds for some reason.
Only disappointments are it is "white" but appears to be Wimbledon White
or some variant thereof, and my truck is what I lovingly refer to as
"Refrigerator White..."  oh well, I can always respray it if it bothers
me too much.

Anyway, real question is this.  the new cap has a third brake light
molded in above the door, but my truck didn't have a third brake light
from the factory.  I'm ASSuming that what I need to do is to intercept
the brake light wiring between the switch and the steering column, and
run a new wire to the rear of the truck, but before I do, there isn't a
pure brake light signal available anywhere at the rear of the truck is
there?

thanks,

nate

Signature

replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

lugnut - 25 Feb 2008 04:16 GMT
>Just picked up a fiberglass cap off craigslist for my '93, I'm happy
>because they seem to be hard to find for shortbeds for some reason.
[quoted text clipped - 14 lines]
>
>nate

Dan't know how much you know about electrical stuff.  We'll
probably need some guidance on that side.  What I did on
mine is use a tap to the brake/turn circuit on each side in
the rear.  It is easy to run the wire down the stake hole to
the lamp or the harness on each side.  You can get to it
easily by removing the tail light assembly.  Went to radio
Shack and got a couple of diodes.  Sorry, I don't remember
the exact value.  I think the idea is to get something
higher than what is actually needed.  The feed from each
brake lamp circuit gets one turned the correct way to feed
power to the lamp.  They will join together at the lamp to
feed the third lamp.  Ground the lamp as you normally would.
What happens is you have power to the third brake lamp from
either brake lamp.  The diode prevents a crossfeed to the
other side so that the brake lamps do not know what the
other is doing when the turn signal is working.  I don't
recall the specs on the diodes.  I think the big thing is
handling the wattage rating of the lamp.  You will need to
check that to get the right diode.  Seems to me that the
ones I got were rated for 50 watts or so each which is well
above what I needed.  You can find the brake light feed at
the lamp pigtail by just turning on the turn signal while
you probe them with a test light to find power.

Lugnut
N8N - 25 Feb 2008 14:59 GMT
> On Sun, 24 Feb 2008 19:51:58 -0500, Nate Nagel
>
[quoted text clipped - 43 lines]
>
> Lugnut

I'm pretty handy, but I'm having a hard time envisioning what the
diodes would accomplish here - wouldn't that allow the light to flash
when either turn signal was activated but you *weren't* braking?  I've
also found some "logic modules" intended for this application but I'm
having a hard time envisioning how one could be 100% foolproof; I've
been drawing a couple logic diagrams in my head and the best one I
could come up with still could be fooled if you had the turn signal on
and stepped on the brake during an "OFF" period for the active turn
signal and therefore the third brake light activation would be delayed
by a second or so.  Since the whole purpose of the light is to give
fast and unambiguous indication of brake activation it seems like I
should just run the wire and be done with it.

Some sites I've found have indicated that a '93 *should* have a third
brake light in the back of the cab from the factory, but mine does not
- it's only a cargo light.  Do you think the wiring would still be
there from the factory?  I can't check as the moment as the cap is on
the truck (how else was I going to get it home?) and I don't have a
handy helper to remove it again (but I will have to as it is just
sitting on the rails with no tape; I bought it yesterday so didn't
have the opportunity to stop at my FLAPS and pick up some tape on the
way.)

thanks,

nate
lugnut - 25 Feb 2008 15:51 GMT
>> On Sun, 24 Feb 2008 19:51:58 -0500, Nate Nagel
>>
[quoted text clipped - 70 lines]
>
>nate

I can't find the diagram that was originally used.  I did a
quick Google and found this which may be the ticket for you

Tiny URL:  http://tinyurl.com/2ejg5f
bill gammon - 26 Feb 2008 15:06 GMT
> Just picked up a fiberglass cap off craigslist for my '93, I'm happy
> because they seem to be hard to find for shortbeds for some reason.
[quoted text clipped - 17 lines]
> --
> replace "roosters" with "cox" to reply.http://members.cox.net/njnagel

Just cut into the exsisting brake light wire at the rear of the truck
put a weatherproof connection on and wire in the 3rd brake light. A
word of warning, if the Cap brakelight is on the door of the cap be
prerared to repace the wiring every once in a while. Reason as you
open the cap door you are bending the wires and they will break.
N8N - 26 Feb 2008 15:28 GMT
> > Just picked up a fiberglass cap off craigslist for my '93, I'm happy
> > because they seem to be hard to find for shortbeds for some reason.
[quoted text clipped - 23 lines]
> prerared to repace the wiring every once in a while. Reason as you
> open the cap door you are bending the wires and they will break.

That's the thing, *is* there a brake light wire?  Where should I be
looking for it?

thanks,

nate
Whitelightning - 27 Feb 2008 03:26 GMT
On Feb 26, 10:06 am, bill gammon <bill.gam...@sympatico.ca> wrote:
> On Feb 24, 7:51 pm, Nate Nagel <njna...@roosters.net> wrote:
>
[quoted text clipped - 3 lines]
> prerared to repace the wiring every once in a while. Reason as you
> open the cap door you are bending the wires and they will break.

That's the thing, *is* there a brake light wire?  Where should I be
looking for it?

No there is not "just" a brake light feed wire at the rear. And unless the
feed is aquired
before it goes through the turn signal switch, its going to blink when you
use the trun signals for the side you pulled it from because the brake light
and turn signal use the same feed wire on each side.  The turn signal switch
breaks the conection to what ever side is activated to blink, otherwise both
would blink.
I happen to think third "eyes" are a good idea, anything that might catch
the attention of some idiot doing everything under the sun behind the wheel
but drive and keeps him/her from rear ending me is a good idea.  I always
like to put some lights in the cap so I can see what I might be searching
for at night, so running an extra wire from the brake light switch wouldnt
be a big deal for me.  I  use a 4 wire trailer connector to run barke light
power and ground as well as power feed from a switch in the cab to the cap.
and since I am an old trucker as well, I usually like few clearance lights
on the cap, which the four wire conector allows me to do.  This also gives a
quick disconnect when I need to remove the cap.

Whitelightning
Pete C. - 27 Feb 2008 00:13 GMT
> Just picked up a fiberglass cap off craigslist for my '93, I'm happy
> because they seem to be hard to find for shortbeds for some reason.
[quoted text clipped - 18 lines]
> replace "roosters" with "cox" to reply.
> http://members.cox.net/njnagel

If the truck doesn't have a CHMSL, the cap isn't required to have one so
you could simply ignore it. On my truck the CHMSL is fed directly off
the brake switch. The regular stop/turn lamps are fed from a stop lamp
relay that feeds the turn switch. If you have a relay I'd try to tap the
output from there.
wstiefer - 28 Feb 2008 05:19 GMT
I found the wiring diagram.
The third stop light is fed straight from the stop light switch.
LT GRN color.
You could buy a kit that has the logic curcuit as well as the lamp housing,
been there, done that.

wws

> Just picked up a fiberglass cap off craigslist for my '93, I'm happy
> because they seem to be hard to find for shortbeds for some reason.
[quoted text clipped - 18 lines]
> replace "roosters" with "cox" to reply.
> http://members.cox.net/njnagel
N8N - 28 Feb 2008 20:23 GMT
You have a wiring diagram?  which manual is it in?  I looked all
through the body service manual last night and couldn't find it.
(yes, I did buy some used manuals off fleaBay)

nate

> I found the wiring diagram.
> The third stop light is fed straight from the stop light switch.
[quoted text clipped - 28 lines]
>
> - Show quoted text -
lmcclaf - 29 Feb 2008 00:39 GMT
http://www.fordf150.net/howto/wire3rdlight.php

This article says for 97 and newer but there might be something
similar in your wiring harness. Probably not but it doesn't cost
anything to read the article.

Cheers,
Lawrence
wstiefer - 29 Feb 2008 03:25 GMT
ME?, no.
Online reference: http://search.ebscohost.com/
user id:  lib
password:  access

Pretty neat, huh?

wws

You have a wiring diagram?  which manual is it in?  I looked all
through the body service manual last night and couldn't find it.
(yes, I did buy some used manuals off fleaBay)

nate

On Feb 28, 12:19 am, "wstiefer" <wstie...@sbcglobal.net> wrote:
> I found the wiring diagram.
> The third stop light is fed straight from the stop light switch.
[quoted text clipped - 32 lines]
>
> - Show quoted text -
Nate Nagel - 01 Mar 2008 00:05 GMT
Sweet.  yeah, that's more like what I need, just something simple that
tells me about where to look and what color wire to use.  thanks a bunch!

nate

(bookmarking site for future reference)

> ME?, no.
> Online reference: http://search.ebscohost.com/
[quoted text clipped - 52 lines]
>>
>>- Show quoted text -

Signature

replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

N8N - 03 Mar 2008 13:34 GMT
Follow up - got it done yesterday, I just ran the wire because a) I
was adding mechanical oil pressure and vacuum gauges anyway so I had
to drill a hole in the firewall anyhow and b) I just didn't see how a
logic module would work perfectly all the time.  So it's done.  I
found a connector under the center of the dash with a brake light
signal on it, just tapped off of that with a scotch-lock.  Also found
that there is a pressure tap for the trans with 1/4" NPT thread right
above the pan on the driver's side, that's where I put the temp.
sender for the trans temp. gauge.  all back together now, hands are a
little busted up but truck is ready for inspection as soon as my new
cap door latches show up (might be here today or tomorrow)  Probably
the most frustrating part of the job besides running the wire in the
split loom all the way back (hint: I used about a 18" piece of solid
THHN with an uninsulated crimp connector on the end of my new wire to
push it through tees, etc.) was finding gauge power - there's not a
whole lot of slack in the wires behind the gauge panel, but I got it
done.

For the first time in about six months I have the facia back on the
dash so the truck doesn't look so "ghetto" (I never did get the oil
pressure gauge in the dash working properly; I had a mechanical gauge
zip tied to one of the vent openings, I finally mounted a proper three
gauge panel as part of this whole exercise) but my vents are still all
busted, I haven't bothered to look for replacements, new ones from LMC
are expensive!

thanks to all

nate

> Sweet.  yeah, that's more like what I need, just something simple that
> tells me about where to look and what color wire to use.  thanks a bunch!
[quoted text clipped - 64 lines]
>
> - Show quoted text -

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