Running lights not working - how to troubleshoot?

[orggardn]

I had an odd problem when I connected the 7 pin connector to my F150. Usually, I turn my headlights in full "on" mode, so when I'm behind the truck and the connector seats - I see the running lights come on.

On Friday, I tried and no running lights. Must have fiddled with it for 20 minutes, with a sickening feeling that the trip may have to be cancelled. I finally thought, I'll try the turn signals....sure enough turn signals and brake lights worked. No running lights, no tail lights. I checked the dash and the trailer sensor for brakes connected was functioning properly. Since we would travel both directions in the daylight, we went on, without incident.

Now that I'm back, I need to get that resolved, but don't know where to start. In the truck? In the trailer? At the connector? My trailer wiring IQ is pretty low..... so suggestions in newbie terms please.

Thanks.

**NOTE: item of note. I had an electric jack installed since the last time we went out. Is there perhaps a connection there?

[orggardn]

As always.... great feedback. I really like the looks of the tester. I figure if I can isolate one side of the equation, surely I can solve for the other.....

[Gene_Ginny]

westend wrote:
...There is only one deoxidizing spray solution to use and that is Caig brand Deoxit. Dielectric grease eliminates oxidation. WD40 is for lawn mower spark plugs that get wet and not much else. ...

I have worked in the electronics world since '62. In the last 20 years I have used WD40 to resolve MANY intermittent electrical connector issues including those old computer boards with the printed circuit edge connectors that went into the mother boards. (remember them?) I have seen many people fix light bulb socket problems with WD40. Sorry you don't agree but I have been there, done that for a lot of years.

[westend]

Gene&Ginny wrote:

RoyB wrote:
... I also squirt wd40 into the connector at times and wiggle the 7-way plug around some to clear away some of the debris...

Roy Ken

I can vouch for the WD40, it does wonders on marginal connectors. It is easy, quick, and inexpensive and far better than that grease stuff.

There is only one deoxidizing spray solution to use and that is Caig brand Deoxit. Dielectric grease eliminates oxidation. WD40 is for lawn mower spark plugs that get wet and not much else. WD40 is primarily coconut/palm oil and solvent. It will dissolve certain rubber products. The reason so many use it is because it was one of the first lubricant products in a spray can. I can't say enough bad things about it.

About the fusing question. In my Superduty there is a separate fuse for parking/marker lights. It is in the main fuse panel below dash. I have blown it a number of times while using my utility trailer. That has probably more to do with the lighting system on that trailer than anything. Still, a first diagnostics step is to see if there is power at the truck's trailer harness when the truck's lights are on. I linked to the different connection schematics, pin locations, and color schedules in my first post.

You do have a test light or meter available?

[Gene_Ginny]

RoyB wrote:
... I also squirt wd40 into the connector at times and wiggle the 7-way plug around some to clear away some of the debris...

Roy Ken

I can vouch for the WD40, it does wonders on marginal connectors. It is easy, quick, and inexpensive and far better than that grease stuff.

[Bobbo]

RoyB wrote:
I got one of these 7-way testers from AMAZON... You plug this in place of the trailer plug and if all of the lights work good here then the problem is on the trailer side...


I also squirt wd40 into the connector at times and wiggle the 7-way plug around some to clear away some of the debris...

Roy Ken

I agree with this post. It tells you in an instant which side of the electrical connection the problem is on, eliminating half of the possibilities in an instant.

Only, I prefer This 7pin/4pin Tester since it also tests a 4 pin connection.

[myredracer]

You might try inspecting the connections in the junction box in the A-frame where the umbilical cord wires splice to the trailer's wiring. The connections are exposed to water, dirt and maybe salt from when it was originally delivered plus sometimes the factory does a really poor job of the connections. On our TT, the running lights have a ground and positive connection with a 2-wire cable in the junction box and there is a common ground for all circuits to a ground lug on the frame. Check that all the ground wires bundled and spliced together under a wire nut inside the box is good. If you don't have one, I'd get a voltmeter/multimeter to help in diagnosing.

You could always open up the splice to the marker lights and see if you can get them to come on by jumpering to a 12 volt power source.

A typical TT wiring diagram is below. They can vary between TT manufacturers so don't use this as a standard diagram. Ours does not use the center pin #7 for ex. Disconnect the TT battery before playing around with splices in the box.

If you do end up going into the junction box and find poor connections, you may want to think about redoing all of them. Some (like me) have moved the connections inside a watertight box and used better wire connectors. I had the main positive wire fall right out of a ring terminal when I touched it which could have had serious consequences.

[MEXICOWANDERER]

THIS IS A RELIABLE TOW / TRAILER CONNECTOR




https://www.waytekwire.com/images/items/7way-SplitPin-Trailer-Connector-Socket-37668_f.gif

See the SPLIT PINS in the socket? That's because a tiny screwdriver can be inserted into the slit and the pin spread to maintain superb TWENTY FIVE AMPERE rated connection and transmission.

If I had anything to do with US DOT I would have outlawed junky trailer garbage connectors forty years ago. They are that bad in comparison.

The mounting holes were the same for many years. Without looking...

WHITE: Chassis negative
BROWN: Tail lamps
BLACK: Clearance
GREEN: Left turn
YELLOW: Right turn
RED: Brake (lights or electric brakes)
BLUE: Aux (could power charge lead line)

Starting in 1970 you could not pay me ten thousand dollars to run "R.V. Junk Connectors". I must have saved 500-hours in troubleshooting after I switched over. Show that RV connector to a trucker and he'll be rolling on the ground with fits of laughter.

[RoyB]

I got one of these 7-way testers from AMAZON... You plug this in place of the trailer plug and if all of the lights work good here then the problem is on the trailer side...


I also squirt wd40 into the connector at times and wiggle the 7-way plug around some to clear away some of the debris...

Roy Ken

[chris3403]

Since like me you have a Ford I would also check the High Current Fuse located under the hood. If you forgot to disconnect and the harness pulled then you probably blew the fuse. Happened to me twice. You'd think I would have learned the first time.

[Kit_Carson]

Fuse is bad or ground is not cleaned.

[enblethen]

Check for a trailer connector fuse. It could be located in fuse block under the hood or under the dash. Check the owner's manual.

[orggardn]

I did take a small file and hit the trailer side connectors with it to get a clean(er) base. I did not do the truck side.

You know..... seems like I was having to wriggle it a bit a while back to get it work. Sounds like a good cleaning is in order.

Westend - are you saying your truck has a separate fuse for just the lights? and brakes and signals is on another? If it's a single fuse, then I don't think it's that as I had turn signals and brakes, just no running and tail lights.

Thanks guys.....

[Dick_B]

Awhile back I had to `drill' out the sockets on my connector due to corrosion. Obviously using a small dia drill soas not to make the opening larger. But it's the only thing I could think of that would clean out the hole.
I now spray Corrosion X on the contacts when I think of it. Guess I better do that today!

[fla-gypsy]

Sometimes I have to wiggle my 7pin connector to get everything to work. When was the last time you cleaned the contacts in the plug and the receptacle?