Trailer/towing electrical issue

This is my first post so thanks in advance for info and time

No previous issues with boat trailer/utlity trailer lights before. Headed home from lake this evening and noticed my running lights were out....i do have brake lights and reverse lights on trailer did work.
The plug has only 1 or 3 red lights illuminated. The plug has a T an L and R...the T is only one illuminated.
I checked fuses under hood and under dash and all looked okay.
I guess next is to see if power to plug?
Anyone have any hints

 

Make sure it’s not a truck problem. Check your power and ground at the pigtail harness on the truck. Could be a trailer problem

 

I’d get a test light.
Or a good volt meter.
Then run checks below.

If the truck HAS tail lights and the trailer does NOT check the 30amp towing fuse.
If the 30 amp fuse is GOOD, check the towing Tail Light Relay.
It the Relay is good, check power at the connection on the Trailer light Connector.
If power is to the pin on the trailer light connection then check trailer wiring.

I’d personally start at the trailer light pin connection.
If it has power, then you have a trailer wiring issue.
If it does not have power, then it is a truck side issue.

Visit link below for Tow Connector Diagram.
https://www.tacomaworld.com/threads/7-pin-trailer-connector-wiring-diagram.455153/

 

Are you using a 4 to 7 pin adapter by chance? If so, mine does this from time to time too. If I twist the plug just slightly in the receptacle, they start working normally again.

 

Same on 4 to 7 if that twist does not work I have to clean the pins on the truck receptacle and have also on both the adapter and 4 pin on the trailer (ground is exposed and corrodes).

 

Welcome to the forum. My experience has been that a very large portion of trailer lighting issues are ground related. I've seen some really strange looking things caused by a poor ground. I'd eliminate that potential FIRST.

 

So I'll have truck tail lights truck hazard lights truck turn signals are all working on my truck so it's between the truck and the plug I'm assuming. Brake lights on a trailer work running lights don't......

 

Are you using a 4 to 7 pin adapter???

 

Yes i have adapter from 7 round to 5 flat (i have reverse lights on trailer)
So i think i found it....i had power to plg thru adapter to front of trailer...i had inlight marker lights that when blown interrupted circuit....i changed those and completed circuit.

Lotta fuss when i should've started there anyway

 

Glad you got it figured out. Electrical problems are the worst!