Post by vikx on Apr 23, 2014 22:46:39 GMT -8
When the lights don't work on your trailer:
If you suspect the vehicle wiring, test the tow vehicle for proper 7 way Universal connections. It is the RV industry standard. Any RV shop can test the vehicle and most will do it for free. If a PO wired the truck/car, and it is not standard, that can cause all sorts of interesting problems. Clean the vehicle ground and be sure it is attached securely to the frame.
Note: Sometimes the vehicle can be wired per the 4 way code but use a 7 way connector. This is not correct.
4 way code: White is Ground, Brown is Running Lights, Green is Right Turn, Yellow is Left Turn
7 way code: White is Ground, Brown is Right Turn, Green is Running Lights, Red is Left turn
7 way note: Black is 12 volt hot, Blue is Brake hot, Yellow is Aux or Spare, seldom used.
You can see why the lights would be screwy if the codes are mixed up!
On to the trailer:
Check to see that the wiring to and from the front J-box is good. Look for compromised wiring, frays and teeth marks.
All trailer GROUNDS must be clean and secure to the frame. Sometimes, it is necessary to run a small ground wire from the skin to the frame. WHEN IN DOUBT, GROUND IT AGAIN.
Never use a vehicle to test the trailer wiring. Use a portable jump battery and a 7 way receptacle with Ground, LT, RT and TM (tail/clearance lights) wires.
Connected to the trailer 7 way plug, it is easy to test what's what.
1. Ground the battery and WHITE receptacle wire to the frame.
2. Isolate the Hot Clamp so that it will not ground out against the trailer metal.
3. Touch the Green wire to the Hot clamp. All TMs should glow.
4. Touch the Brown wire to the Hot clamp. RT should glow brightly.
5. Touch the Red wire to the Hot clamp. LT should glow brightly.
If your trailer has all purple wiring, you can still test it. It takes a little more time, but each wire can be labeled according to which light(s) is activated. Be sure the Ground is good and the lights are clean before testing. If nothing works, check the grounds again.
If you suspect the vehicle wiring, test the tow vehicle for proper 7 way Universal connections. It is the RV industry standard. Any RV shop can test the vehicle and most will do it for free. If a PO wired the truck/car, and it is not standard, that can cause all sorts of interesting problems. Clean the vehicle ground and be sure it is attached securely to the frame.
Note: Sometimes the vehicle can be wired per the 4 way code but use a 7 way connector. This is not correct.
4 way code: White is Ground, Brown is Running Lights, Green is Right Turn, Yellow is Left Turn
7 way code: White is Ground, Brown is Right Turn, Green is Running Lights, Red is Left turn
7 way note: Black is 12 volt hot, Blue is Brake hot, Yellow is Aux or Spare, seldom used.
You can see why the lights would be screwy if the codes are mixed up!
On to the trailer:
Check to see that the wiring to and from the front J-box is good. Look for compromised wiring, frays and teeth marks.
All trailer GROUNDS must be clean and secure to the frame. Sometimes, it is necessary to run a small ground wire from the skin to the frame. WHEN IN DOUBT, GROUND IT AGAIN.
Never use a vehicle to test the trailer wiring. Use a portable jump battery and a 7 way receptacle with Ground, LT, RT and TM (tail/clearance lights) wires.
Connected to the trailer 7 way plug, it is easy to test what's what.
1. Ground the battery and WHITE receptacle wire to the frame.
2. Isolate the Hot Clamp so that it will not ground out against the trailer metal.
3. Touch the Green wire to the Hot clamp. All TMs should glow.
4. Touch the Brown wire to the Hot clamp. RT should glow brightly.
5. Touch the Red wire to the Hot clamp. LT should glow brightly.
If your trailer has all purple wiring, you can still test it. It takes a little more time, but each wire can be labeled according to which light(s) is activated. Be sure the Ground is good and the lights are clean before testing. If nothing works, check the grounds again.