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Trailer wiring issues pt 1


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Hi guys,I have just fixed an issue with one of my stop lights working  intermittently  on my trailer and have a few tips to share for those of you that may be experiencing electrical issues with your trailer.

Most electrical issues on  boat trailers stem from either blown fuses,bad grounds,blown bulbs,corroded/broken terminals,shorts in wiring where they've rubbed through,Loose terminals,fasteners etc.

Always check your fuses and bulbs thoroughly before advancing to checking the circuits with a test light. 

All the simple tests I'll conduct using a simple inexpensive 12v test light although you can use a multimeter also.

To determine if there's an issue with the cars trailer plug or wiring  you want to test the female plug on the car first.

In this example I have the ignition on in the car and have switched the right indicator on.image.jpgWhat I have done is clipped the test light to a ground/earth, in this case the tow bar and touched each and every pin with the test light until I found power indicated by the flashing test light telling me there's power to the right turn signal.

Repeat the process for the remainder of the terminals to find if the left indicator,stop lamps,parkers have power.

(When testing the indicators the test light will flash in sequence with the tail lights on the car,where as the stop,parkers etc will keep the test light illuminated).

Lets say the cars trailer plug  passed all the tests on each of the terminals ,now you'd remove the cover on the male end of the trailer plug and plug it into the female plug on the car and repeat the tests again.

This time on the male end of the terminals like this.image.jpgAs you can see the test light is lit up indicating there's power and all other terminals tested positive also.

Now I'll move on to the contacts at the lights themselves and test for power across both contacts.image.jpgAs you can see I've got power across the bulb holder terminals.

A tip for you guys with incandescent trailer lights is to solder the bulbs onto the bulb holders using a butane cigarette lighter and solder as it stops them from vibrating loose and losing contact like I do if you don't want to go the led route.

Cont pt 2.




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