Need Help with trailer lights.

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Malia Kai

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C Dory Year
1994
C Dory Model
22 Cruiser
Vessel Name
Malia Kai
I just had some new lights installed on my trailer. The installer checked all of the lights with a 12 volt battery charger and all lights were working so he insists that the problem must be with my tow vehicle. The problem is this : Brake lights and turn signals are working well but there are no tail lights when I turn on my vehicle's headlights. Is there anyone with suggestions as to what the problem may be.

Frustrated in Hawaii.
 
Check to see if the tail light wire has a good connection on your vehicle plug, tight and free of corrosion. Make sure the pin for that circuit is clean on the vehicle side.
 
We had this problem over the summer. We never have the boat behind the truck during the night - just so happens that we did and the tail lights went out. The brake lights and directionals were fine, but no running lights/tail lights on the trailer (all the truck lights worked fine).

We have a 2001 F150 and it turned out to be a fuse (something like "towing parking lamps") under the hood. If you have a F150, let me know and I'll find out the fuse number.
 
Out of curiosity, are you driving a Toyota or Honda? The wiring in my Toyota does not match my US standard wiring in the trailer. "Creative wiring" and operation is required to use all trailer lights. My truck cannot pull Napoleon on the highway so I have not bothered to address it.

When my buddy with a GM truck tows my boat the wiring standard matches up and all works perfectly.
 
Matt

That sounds like a production problem. I tow with an 07 Toyota and tow many trailers with it. U-Haul, several different types of boats and al the wiring works fine. On our Honda Pilot we had to add the 5th wire for the brake solanoid, since for some reason Honda only does a 4 wire flat on the tow package. Don't get me started on the Toyota Tacoma truck. I will never buy another Toyota, as the dealers pat answer for all wierd noises or problems, is "thats normal, they all do that. If that was so there would not be any trucks people would want to buy with all the racket they make.
 
The tail lights are brown wire and the ground is the white wire. Take a volt meter or at least a 12 volt lamp tester (I soldered aligator clips to a 12 volt lamp bulb). Check for 12 volts (or the light coming on) between the bare metal pin on the truck 4 contact flat connector and the first connector which is inside of the rubber shield (this will be the brown or tail light).

if this does not light up or measure 12 volts, then you have to trace the circuit back to the tail lights. You can split off from one of the tail lights if it is not done properly. Some trucks have a separate fues for the tail lights on the trailer. It is possible that fuse is either blow, or not even in place.
 
I had a problem with my lights that had me pulling my hair out. Voltage and grounds all checked out good. I cleaned the contacts in the plugs and sprayed with contact cleaner and that didn't help. The problem was intermittent so I thought for sure a bad ground. Finally I looked at the male plug coming from the trailer and the contact prongs each had a small slit in them. I took and instrument screwdriver and carefully opened the gap in effect increasing the diameter of the prong so it made a more solid contact. Haven't had a problem since. In other words where the trailer plugged into the truck even though new wasn't making good contact.
 
Let's see, there's a plug in the rear of the truck which supplies power to the trailer lights. That plug is a 4 pin if you're only powering lights. It's a 7 pin if you're towing a RV. In either case there has to be voltage coming out of that plug for each circuit that needs power. No power at the connector, no work.

For the taillights, there should be 12 VDC on the "correct" pin to the taillight circuit. It's easy to check with a voltmeter, which costs $3 at Harbour Freight. If it's a 4 pin, check each pin to ground (the bumper will do), and I mean all 4, and find out which is ground, which powers the left & right turn and which is the taillight. Do this by turning the proper switch on/off. Bob is right, the taillight should be a brown wire, but who knows? If a particular pin doesn't have power when it should, fix it. If everything comes out right at the truck side, attach a 12V battery to a pair of wires and see what pin on the trailer side powers what light. If both sides arre OK, do what Marvin suggested and try spreading or cleaning the pins.

For a 7 pin, find out how its wired, as I've found out (to my amazement and sorrow,) that there's no standard way. Then check to see if it matches the trailer and there's power on the right pin.

I'm surprised that the person who supplied the lights didn't do this for you, but just dumped the problem in your lap. Hopefully that installation was free.

Boris
 
On my 2004 Dodge diesel the trailer tail light circuits are fused separately from the truck tail lights. That drove me nuts until I finally realized it. You can have truck lights working and no trailer lights and visa versa.
 
Don and Brenda":25zwm1bo said:
Matt

That sounds like a production problem. I tow with an 07 Toyota and tow many trailers with it. U-Haul, several different types of boats and al the wiring works fine. On our Honda Pilot we had to add the 5th wire for the brake solanoid, since for some reason Honda only does a 4 wire flat on the tow package. Don't get me started on the Toyota Tacoma truck. I will never buy another Toyota, as the dealers pat answer for all wierd noises or problems, is "thats normal, they all do that. If that was so there would not be any trucks people would want to buy with all the racket they make.
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Hi Don,
Without taking another look, either my truck or my trailer uses a single wire for two functions whereas the other uses two wires for the same thing. For some reason I want to say one has a brown wire with a white stripe and the other requires two wires for the same functions. The brown wire with white stripe does two functions.

When I explored this further, I heard from others that echoed the same, I was told there is a US standard and a Japanese wiring standard.

Again, I would need to be sitting down looking at the wires to describe it in more detail. My trailer connects directly with full functions on my buddies GMC.
 
As we have all found trailer wiring can be quite a challenge at times, and sometimes requires more alcohol than others to complete the task at hand.
 
There's no substitute for some electrical know-how, a few tools, including a circuit tester, an understanding of vehicle and trailer circuits, and some reasonable degree of problem solving ability when trailer light issues arise. Even then, sometimes the problems seem baffling!

Lose your taillights, or can't hook 'em up on the way home with that new/used boat? If worse comes to worse, and you can't get them to work, don't over look the obvious:

Tape a red piece of plastic or cloth over a flashlight or lantern and tape it in turn to the back of your trailer. You still won't have brake lights or turn signals, but the 18 wheelers and little old ladies doing 75 won't have an excuse to run you over, and the Highway Patrol may just let you off since your making a valiant effort to comply with the law as far as you can under the circumstances.

I've towed several "new" sailboats home that way with a red-covered flashlight taped to the end of the mast!

Joe. :teeth :thup
 
Sometimes, I get best results working on trailer lights after two in the morning when I'm planning to leave home at 6 AM.
 
Matt Gurnsey":2o9w9h7d said:
Rule number 1 when weird things are going on with trailer lights- check the ground.
Click to expand...

YES!

Better yet: Take out TRIPLE GROUND INSURANCE!

1. Ground the trailer pigtail to the frame solidly, while also-

2. Running a ground wire back to each bulb receptacle/light, and

3. also ground each receptacle/light to the frame nearby.

This way, there are no ground fault problems, which comprise about 1/4th to 1/3 rd (a guess) of all simple trailer light problems.

Welded trailers probably have fewer ground problems, and bolt-together trailers more, because of the better connections between bonded parts as compared to mechanically connected ones.

The redundancy may see unnecessary to some, but once done, that source of problems is eliminated, unless, of course, you launch in salt water routinely, don't disconnect your lights when doing so, and let the trailer set around with salt on and or in it for hours or days. If you do, all bets are off!

Joe. :teeth :thup
 
Thanks all,

My wife took off in my truck this morning to go surfing, but when she returns I will be following the advice posted here as it sounds promising. I can't even take my boat out here in Hawaii, as you have to have an annual safety check on all trailers and all lights must be operational to pass it. They give you a sticker to stick onto your trailer when it has passed safety. Also, you cannot renew your trailer registration unless you have passed the safety registration. I tried going fishing one time without the renewals and I received a $200 ticket at the launch where I had parked my trailer to go fishing. Apparently there are government employees that drive around to all of the boat launches and issue citations to the non-compliant. Will let everyone know what the problem was once I find it.

On the brighter side of things, I was able to catch a 90 lb. ono(wahoo) a few weeks ago before all of this came up. Biggest fish that I have caught so far although I am equipping up to start night fishing next summer to go for some of the 200 to 300 lb. yellow fin tuna they catch here off of Kona every summer and fall.
 
Malia Kai":1bcnzt75 said:
I am equipping up to start night fishing next summer to go for some of the 200 to 300 lb. yellow fin tuna they catch here off of Kona every summer and fall.
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If you don't catch any big tuna, you might try hooking into a jet ski or two. Probably be about the same experience, no?

Joe. :lol: :thup
 
Malia Kai":1793mlsi said:
Thanks all,

My wife took off in my truck this morning to go surfing, but when she returns I will be following the advice posted here as it sounds promising. I can't even take my boat out here in Hawaii, as you have to have an annual safety check on all trailers and all lights must be operational to pass it. They give you a sticker to stick onto your trailer when it has passed safety. Also, you cannot renew your trailer registration unless you have passed the safety registration. I tried going fishing one time without the renewals and I received a $200 ticket at the launch where I had parked my trailer to go fishing. Apparently there are government employees that drive around to all of the boat launches and issue citations to the non-compliant. Will let everyone know what the problem was once I find it.

On the brighter side of things, I was able to catch a 90 lb. ono(wahoo) a few weeks ago before all of this came up. Biggest fish that I have caught so far although I am equipping up to start night fishing next summer to go for some of the 200 to 300 lb. yellow fin tuna they catch here off of Kona every summer and fall.
Click to expand...

Ah, the summer Ahi run AND a 90 lb ono! 8) Damn....Aloha, bruddah.
 
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