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F100 351
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74 Posts
Discussion Starter #1
my 86 f100 ute has no reverse lights, no lights setup on the back tray.
can some one just quickly give me a quick 101 leason with how
the light comes on when reverse is selected.

correct me if i'm wrong. i have 4 wires coming from the selector switch
on the side of the c4 trans, one would be for reverse. that would go
to a fuse then out to the back to light up?? thats my understanding

i checked for voltage on the 4 wires coming from the trans and aslo
every wire out back. one wire from the trans showed voltage when
motor is running. ive sorted out tail light, brake light and indicators
out the back. but then there are still 4 wires that have been cut and
taped up with no voltage wen in reverse. i'm stumped...........any one
have any tips to diagnose what or where my problem lies
 

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F100kls said:
correct me if i'm wrong. i have 4 wires coming from the selector switch
on the side of the c4 trans, one would be for reverse. that would go
to a fuse then out to the back to light up?? thats my understanding
i checked for voltage on the 4 wires coming from the trans and aslo
every wire out back. one wire from the trans showed voltage when
motor is running. ive sorted out tail light, brake light and indicators
out the back. but then there are still 4 wires that have been cut and
taped up with no voltage wen in reverse.
2 of those wires are for reverse lights and 2 for neutral start switch.
For safety reasons they all need to be hooked up. so the car can't start in gear.
The reverse lights may not go directly to the fuse box but they do go through the indicator switch.
You need a test lamp and maybe a multimeter.
It'll take some sorting.
 

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74 XB Fairmont
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5,113 Posts
2 of the wires are your inhibitor switch (stops you starting in gear). The other 2 are the reverse lights.

Those wires are supposed to run into a 4 pin plug in the loom on the firewall.

What colors are the wires. I have a vague idea from when I used to have a factory shifter.
 

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F100 351
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74 Posts
Discussion Starter #4
brenx, 2 red 1 purple 1 black. i got voltage from the only one of the red wires, when motor is running either in neutral or drive.


northey, you said reverse do go through the indicator switch. where is that?
 

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blinker switch is behind steering wheel directly attached to blinker stalk.
reverse lights are attached to it because rev lts are blinker lts too.
sounds to me too that inhibitor switch is the red wires.
It should only have power to one wire when in park and neutral obviously.

You need to find which wire is reverse lt power wire and check its continuity. Make sure it has power where it leaves the blinker switch. A mate's blinker switch had a faulty terminal which we could not repair. It is a common fault and it took ages to find the problem because we never thought to look there.
 

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F100 351
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74 Posts
Discussion Starter #7
ok removed indicator switch assembly, have'nt checked for continuity yet.

but had another look out the back after finding wiring diagrams on a good
f100/bronco site. i now know which is the wire for back up lights and all the
others, but with motor going and in reverse i check for continuity, i get
1 bar out of 4 on my cheapo tester.
so then i thinking every thing is still wired together for reverse to work...............
but there isn't enough power to get a 5watt globe going.

brenx, i told lies last nite the wire that shows voltage is the 1 purple wire. theres
volts when in P, D and R???? is this right. the other three were 2 red wire2 at
heavier gauge and 1 black wire none of these show anything no volts no continuity
in any gear.

what do ya reckon goin on?
 

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74 XB Fairmont
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5,113 Posts
That doesn't sound right. Your linkages might be worn? You should show voltage on one of the wires when in "R".

Do any of those red wires have a colored stripe (trace) on them?

Basically all those wires are "+" (positive) wires. There is no earth wire there. So you can't do any damage. To make your life easier. Touch each wire together and check for the reverse lights. When you've found that there will be only two left to connect ;) They'll be your inhibitor switch.
 

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F100 351
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74 Posts
Discussion Starter #9
from the trans the 2 red ones don't have any stripes.

i'll do the arc welding with the other wires soon and i'll let you know what happens
 

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F100 351
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74 Posts
Discussion Starter #10
i have light.......... :whiskey:

i had a bit of a play and with the shifter and found i had to hold the lever up cos it a column shift the lever has some slack in it wasn't engaging the back up lights on. it takes 3-4 attemps to get it workin has to be in the right spot or any slight movement will turn the light off and then it takes another 3-4 tries to get it back on

when i have the motor going and reversing its right on the point of slipping into P so i hope i dont accidently pop into P wen reversing in a hurry

i've hooked up a small spottie with 100w globe directed to the ground jus so i dont blind any one

its bloody good to see where your going now instead of backin into the carport in pitch black dodging the car next to you and watchin you dont hit the wall on the other side. had a couple nights where i jump on mr brake and say F##K that was lucky just stopping 2 inches short of the missus new car :doh:
 

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F100 351
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74 Posts
Discussion Starter #13
made some ajustments with lining up the needle to the selected gears so now its on D instead of looking like its in 2nd, but the inhibitor switch for reverse is dead. it still does P and D tho

i'll get a new one and then all hassles are fixed
 

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F100kls said:
made some ajustments with lining up the needle to the selected gears so now its on D instead of looking like its in 2nd, but the inhibitor switch for reverse is dead. it still does P and D tho

i'll get a new one and then all hassles are fixed
are you sure it's dead? they usually have a thread adjustment on the inhibitor and it may just need slightly altering.
The plunger as it moves in and out changes the circuit continuity same as when it's being moved by the gear linkage.
for instance; plunger in "out" position will have circuit (for Park); in slightly "in" position will have zero continuity (for reverse); then fully depressed will have zero continuity or "open circuit" again (for 1st, 2nd, Drive).
 

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F100 351
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74 Posts
Discussion Starter #15
i did remove the switch off the box and was manually turning the switch myself. i could hear it clicking into position, like your saying

plunger in "out" position will have circuit (for Park); in slightly "in" position will have zero continuity (for reverse); then fully depressed will have zero continuity or "open circuit" again (for 1st, 2nd, Drive).

i'd get into the position that would be reverse but no result ( no lights)
it did pass my mind to pull it apart but i thought i'd do more damage than good
i put it back on and there was still no result.

i'm feeling eager to pull the swich to bits if it will let me
 
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