This is a carry over from a previous post about my LED light install on my flatbed.
I have my tail lights working now so that is ok.
Problem is I've lost my drivers side signal as well the indicator on dash.
Bulb is good, fuses are good.4 ways work.

I have a power leak to the rear LED lights and trailer plug. I'm only getting 3.4 volts out of my trailer plug, not enough to run lights on trailer.
i swapped headlight switch from parts truck, no change.
Had steering wheel appart and looks good in there. I noticed w a 12 v tester that when r signal is on 4 wires are hot and left 3 wires hot.

I have pulled every plug under the hood appart, al grounds have been redone, switched headlight switch, deleted led lights and wired in old bulb style,

Is there any other relays I can check?
Even though multifunction switch in steering is working can it be bad?

 

Did you re-run or repair any wiring for the tail lights when you replaced them? Did it involve any of the splices for the trailer plug?

If not, start by inspecting the wire harness along the frame rail from the left front of the cab to the bumper, but start at the bumper - the area near the bumper is the most common area for problems, particularly on work trucks. Unplug every connector in the harness related to the lights and inspect for corrosion - clean if needed and apply a light coat of dielectric grease to the female side of the connector.

When you checked voltage, were you using a ground independent of the trailer plug? If not, recheck with a frame or body ground - a problem with the ground for the trailer plug could affect the reading.

 

Thankyou for reply,

The factory male plug was still intact on back if truck.
I had the remains of wiring for tail lights including female connector so it was plug and play.
For the trailer wiring I bought a Hopkins T style connector that plugs right in between male/female plug for tail lights.
Other than add wiring to new grounds to attach to studs I put on frame no splicing was done.
I can't see that 3 1/2' feet of wiring that is along frame by fuel cell.
I did follow it from back up to front past F pumps and then up to connectors under hood.
I unplugged all connectors but 1 ( largest bl. Connector ) a real bugger with those clips.
i had hazards going as I unplugged to find correct plug.
There was 1 plug which was fairly corroded and I wire brushed but no grease.
Any voltage checks were done w ground on truck not too plug.

ive been reading up on how to test headlight switch but haven't done it yet.
Also not certain where signals get there power from, through headlight on to multifunction in steering column.

 

Okay I think I misread your first post - thought you meant you weren’t getting a rear driver side signal but after reading it again I’m sure I misunderstood (my fault - stupid brain tries to think for itself sometimes).

So for the sake of clarity, you don’t have a driver side turn signal at the front or rear, and you don’t have the driver side signal indicator; but the passenger side signals/indicator works, correct?

Also, when you select the driver signal, does the light/indicator come on and stay on without flashing or does it not come on at all?

You said the 4 way flashers work, so I’m thinking it may be the turn signal switch that’s bad. The turn signal switch and hazard switch are one assembly, but the hazards draw power from a different circuit than the signals.

I can’t post a complete diagram because the details are split between 3 separate diagrams, but power flow for the signals is:

Battery - Ignition switch (run position) - fuse - signal flasher - turn signal switch - respective bulbs (indicator bulbs tee off signal circuits).

Power flow for the hazards is:

Battery - fuse - hazard flasher - hazard switch - respective bulbs

Considering the flashers work and the signal does not, I think the switch is at fault. If you look at the diagram of the switch assembly (below) you can see that both functions use the same output circuits to make the bulbs flash but utilize different contacts within the switch to operate the signals.

The bulbs working normally during 4 way use eliminates everything downstream (wiring, bulbs, grounds) of the switch. If the passenger signal is working normally, that eliminates everything upstream (power supply, fuse, flasher) of the switch.

 

The 2 main things happening :

1- no front drivers turn signal or indicator on dash.

2- power leak to rear lights ( key on always on dim ) 5.4 volts to trailer plug.




i will look at wiring diagram after work today.

I did manage to fish out wiring at back of truck and exposed wiring ,looked okay.

More testing tonight.

My ignition is stiff to turn and does not rotate back after starting, I see that ignition is first in line for wiring that gives power to

Fuse, flasher then signals ?

Thanks for help.

 

Spent too much time on this yesterday but progress made !
pulled steering wheel appart and cleaned all components and lubricated.
Pulled multifunction switch out and checked cleaned contacts.
Once reassembled the front signal is now working and key tumbler now operates much better.

The only thing left is now to find power leak to rear signals ( LEDs ) and to trailer plug.
You were right griff it was the turn switch needed attention.

 

Glad to hear cleaning the switch worked - I don’t think I’ve ever tried cleaning them - my reasoning is if I’m pulling the column apart to get to the switch anyway, I’m gonna replace it. But that’s me.

Anyway, regarding the voltage to the rear lights - have you checked to see if the dimmer is turned down? It shouldn’t be affecting the exterior lights but if there’s a short in the headlight switch or the wiring harness, it’s possible the dimmer is affecting them. Try checking the voltage or brightness on the tail lights while working the dimmer back and forth.

 

I messed around with light switch yesterday with no results. Even with light switch unplugged the lights are still on dim in back.
I plugged work trailer into truck to see what is happening, as soon as plugged in the truck tai lights go out.
Put signals on and both are flashing but trailer lights are very dim.
Headlights on and lights on truck good , trailer barely lights up.

I checked connections under hood again and found one corroded plug.
Pulled appart , cleaned corrosion and found 1 wire hanging on by a thread. No change after repair.
I seem to have a problem interpretating wiring diagrams, I thought power to tai lights was through headlight switch.
The fact that I still have power ( lights on dim ) to tail lights tells me otherwise.

 

If you've got the towing package power to trailer lights is through a couple of relays next to the under hood fuse box.

 

I'm not sure if I had TT package, I installed the hitch.
To get a 7 pole pug to rear I bought a Hopkins connector which plugs in between male/female factory taillight plug.
Assumed I would simply plug in and get power from there ?

 

You should have lights, but +12v, brakes, and reverse come from a different plug hanging out next to the spare tire on the driver's side of the frame. Those with the factory towing package have two connectors, black and gray, that a separate trailer outlet is plugged into. Check under the hood for the relay box I mentioned, and if you have that crawl under the back and see if you still have the two connectors. They're both round, one has four pins in it the other has three. They might also have covers on them. I went to the junkyard and found an OE trailer harness that was broken, then spliced in a Hopkins plug to the harness pigtails, and plugged it into the factory connectors.

You can cut the connectors off and splice directly to the vehicle wiring if you can't find a trailer harness.

 

I have the grey (4?) wire connector that I have the taillight plugged into.
between these plugs I put the T style connector for trailer.
The other plug on mine has been cut off (2) wire and 1 is live when headlights on.
i checked on my parts truck in which somone added trailer lights as I have done and those 2 wires appear to be for marker lights.
So right now I have the tail lights on dim and very low voltage to trailer plug.
I cannot locate where the trailer relay is ( if I have one )

 

Try removing the trailer plug adapter from the factory harness. If the tail lights on the truck return to normal, there’s a problem with the plug.

The trailer light relay should be under the hood on the driver side near the firewall. The power for the trailer light relay control circuit comes from the headlight switch (or at least it’s supposed to), so if you unplugged the headlight switch and the tail lights/trailer lights were still on, either something is wrong with the relay or there’s a short to voltage on the tail/trailer light circuits.

 

I tried unplugging trailer adaptor and no change.

mrolling, I connected all my lights , brake, running , signal , reverse and licence from that 1 plug only, the main one (grey) thinking I had it sorted out properly before final install.
I ran nothing from where that other plug was ( mine is gone just 2 wires left) I put connectors on thinking I would use for marker lights etc. 1 wire hot 1 ground ?

One other thing to mention, when I pull headlight switch on, radio (stereo) lights go dim.

 

You have all seven pins on your trailer plug wired into the four pin T connector? T connectors by design only give you lights on the trailer; turn signal, brakes lights, and running lights, plus ground. Control for trailer brakes, reverse lights, and +12v come from a different connector on the frame, or must be wired directly to those circuits by hand.

The towing relay box is attached to the under hood fuse box. If you are standing in front of the driver side fender looking down at the fuse box the relay box is on the right side of the fuse box.

A lot of your symptoms sound like they could be caused by improperly wiring the trailer plug. Snap some pictures of your wiring for us.