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Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10620
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I am having difficulty with my boat trailer lights. It is

Customer Question

I am having difficulty with my boat trailer lights. It is a 4-prong flat.
Dave
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.
Hello. My name is***** seems to be the problem?
Customer: replied 1 year ago.
i am hooking up to a new vehicle, i have cleaned the contacts. nothing works on the trailer - indicators, brakes or running lights.
Expert:  Tan replied 1 year ago.
Ok the common to all the lights that is a problem is ground. Do you have the white wire of the flat plug connected to a good clean ground on the trailer frame?
Customer: replied 1 year ago.
i can check that connection
Expert:  Tan replied 1 year ago.
Ok it isn't likely that all the light don't work unless you have a bad ground.
Customer: replied 1 year ago.
i cleaned up the ground, and nothing is any better
Expert:  Tan replied 1 year ago.
How are you testing for voltage? Do you have a ground in the plug of the vehicle?
Customer: replied 1 year ago.
boy, if you saw it, you might be able to trouble-shoot it no problem
Customer: replied 1 year ago.
i have some testers... one that will see if the 12v current is running through
Expert:  Tan replied 1 year ago.
The voltage goes directly to each light. The ground at each light is picked up in the trailer frame. So if you have voltage to each light and no ground they won't work. Now typically the trailer gets a ground through the ball from the vehicle. Not a very good ground source. So you have to get ground through the plugs then to the trailer frame.
Customer: replied 1 year ago.
i used the 12v meter (little light) on the wires and nothing happened. I put it on the battery, and it lit up!ok... yeah, i think it still might be the ground. that is needed for everything to complete the circuit. I think i all drill a hole in the metal on the hitch metal of the car and put in a little screw.
Expert:  Tan replied 1 year ago.
I have found grounds are the biggest issue with trailer lights. What I used to do was fix lights using a 12 volt battery connected to the trailer harness this way you eliminate the vehicle as a possible issue. Once you get the trailer lights fixed then you can deal with the vehicle. I would verify the grounds at each light also. They are usually corroded as well. Post back with questions.
Customer: replied 1 year ago.
ok... i drilled into a good spot on the steel on the vehicle to make for a good ground... the best i can make.. and it still doesn't work. dang!
Expert:  Tan replied 1 year ago.
If you turn the lights on and with your meter touch the brown pin in the plug on the car and the frame do you have voltage?
Customer: replied 1 year ago.
i tried sanding the contacts on the lights in the back - the ground wire that connects to each side.nothingi will try the brown wire
Expert:  Tan replied 1 year ago.
Ok lets be sure we are getting voltage from the vehicle first.
Customer: replied 1 year ago.
i tried the brown wire and the ground / frame and nothing...
Customer: replied 1 year ago.
no light - no voltage
Expert:  Tan replied 1 year ago.
Ok that tells me the vehicle is the problem. Did you have the parking light switch turned on?
Customer: replied 1 year ago.
i turned not he running lights - headlights
Customer: replied 1 year ago.
could it be the fuses in the car? i don't think that is the case, because all the lights, indicators, etc work on the vehicle
Expert:  Tan replied 1 year ago.
Ok that's fine. Then the vehicle is the problem. Are the tail lights on?
Customer: replied 1 year ago.
yes, tail-lights...
Expert:  Tan replied 1 year ago.
If you don't have voltage to the plug the car is the problem. This is the plug on the vehicle you are testing correct?
Customer: replied 1 year ago.
i think i am just going to have to leave this for another day. i can't rally spend much more time on it... not much makes sense, either!
Customer: replied 1 year ago.
thanks, now!
Expert:  Tan replied 1 year ago.
Where does the trailer get it's voltage from the car. If you have no voltage at the plug on the car how can the trailer lights work. The car doesn't come from the factory wired for trailer lights. So something is wrong with the wiring on the car as you have no voltage to the plug.Does this make sense?
Customer: replied 1 year ago.
yes... i ill check that again... i will put a meter on it, and see if i can get it to light up.
Customer: replied 1 year ago.
how much do i own now...i should end our conversation
Expert:  Tan replied 1 year ago.
You only oew what you have already put up as a deposit. There are no extra charges.
Customer: replied 1 year ago.
hey! that is nice.. i was thinking it might be hours at so much per hour. Thanks for the help. Let me look at it more, and think about it.Thanks again!Dave
Expert:  Tan replied 1 year ago.
Ok Dave. Your welcome. Just post back with findings and we can continue. There is one flat price as long as we stay on the same subject. The question even stays open after you have positively rated me. Thank you............Tan

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