View Full Version : Trailer lights are out...
Went to hook up last night and they just all together stopped working. Put lube on the connections but still nothing. Checked fuse in truck (I think I had the right one), but good.
Looking at my truck manual I have notes about where I changed out a relay that was for "trailer tow left turn" or something. There appears to be a relay for each function of the trailer lights so how do I know if I have a bad relay if they are all together not working?
Thanks for the help.
P.S. this is a 9 year old truck.
flipper
10-27-2010, 01:53 PM
What kind of truck? Most trucks have a seprate fuse for the tailer lights. Could be a ground wire too
fstaslp
10-27-2010, 01:59 PM
I would check ground first if all of them are out.
thatsmrmastercraft
10-27-2010, 02:01 PM
Have you checked the connector on the truck to see if everything is working there? Oftentimes when nothing is working, the culprit is a bad trailer ground.
Truck is a Ford Explorer.
Does the trailer ground to the ball/hitch? I just quickly inspected the wires on the trailer with the flashlight last night but didn't see anything that looked out of place.
Also, I keep it at my dad's and I just had him go hook his truck up and it seems to be working on his truck...although he didn't put it through all the motions.
are you guys saying to check the ground wire on the truck?
fstaslp
10-27-2010, 03:00 PM
Sounds like you have a loose ground on the truck side. You need to find where it is grounded. I used to have a harness that used a clip on ground and I would have this same experienced. Now everything is soldered and i haven't had any more issues.
I just went and looked under the truck and the wire looks in one piece. It's the old flat plug style and I only have four wires (have to flip it to de-activate trailer brake and back up - 5th wire).
I can't even see where it would be grounded on the truck side. The wires go from the relay box under the quarter panel to the plug mount on the rear.
thatsmrmastercraft
10-27-2010, 04:39 PM
I just went and looked under the truck and the wire looks in one piece. It's the old flat plug style and I only have four wires (have to flip it to de-activate trailer brake and back up - 5th wire).
I can't even see where it would be grounded on the truck side. The wires go from the relay box under the quarter panel to the plug mount on the rear.
Use an ohm-meter to check the ground on the truck. One end to a good clean ground and the other end to the ground pin on the truck connector.
1redTA
10-27-2010, 06:02 PM
on the couple of things I've trailered the trailer grounds thru the ball to the truck If it is rusty take it for a spin around the neighborhood or a couple of culdesacs
fstaslp
10-27-2010, 07:21 PM
^^
When you only have a few lights, you may be able to get away with this. Typically Mastercraft trailers look like christmas trees going down the road so it is important to have a good, clean ground. IE no paint, rust, tube socks, whatever. Using the ball as a ground may work, but it is probably not going to be reliable.
thatsmrmastercraft
10-27-2010, 07:33 PM
On all 4 and 5 way trailer connectors, the white wire is the ground. On the trailer side it is to be attached to the trailer tongue to an unpainted surface. On the tow vehicle, the white wire is to be attached to a solid ground - again free of paint & corrosion. While there are plenty of trailers that ground through the trailer ball, there is no need to have the trailer connected for the lights to work. Furthermore, I have had plenty of trailers and never had on without the white ground wire.
ahhudgins
10-27-2010, 07:38 PM
The hitch should never be used as the only ground for the lights, that's why some trailer lights flicker going down the road. On a 4 pin flat connector, the WHITE wire should be grounded to the truck ground. The BROWN wire is for the running lights.
You can look and guess all day long, the best thing to do is use a volt meter.
With the truck lights on, connect the negative lead of the DC volt meter to a good metal ground of the truck. Put the positive lead on the brown wire of the plug (coming from the truck). It should be 12V. If not, you have a problem with wiring in the truck. If it is 12V, move your negative lead to the white wire in the plug and you should still have 12V. If not, the white wire isn't making a connection to the truck ground. As one other poster stated, the white wire should be 0 ohms (shorted) to the truck ground.
ahhudgins
10-27-2010, 07:42 PM
On all 4 and 5 way trailer connectors, the white wire is the ground. On the trailer side it is to be attached to the trailer tongue to an unpainted surface. On the tow vehicle, the white wire is to be attached to a solid ground - again free of paint & corrosion. While there are plenty of trailers that ground through the trailer ball, there is no need to have the trailer connected for the lights to work. Furthermore, I have had plenty of trailers and never had on without the white ground wire.
Agreed.
A lot (and I mean a LOT) of people who don't understand basic electricity tell me "You ain't got to have no ground wire hooked up fur the lites to wurk". Then they wonder why their lights work half of the time. :rolleyes:
On all 4 and 5 way trailer connectors, the white wire is the ground. On the trailer side it is to be attached to the trailer tongue to an unpainted surface. On the tow vehicle, the white wire is to be attached to a solid ground - again free of paint & corrosion. While there are plenty of trailers that ground through the trailer ball, there is no need to have the trailer connected for the lights to work. Furthermore, I have had plenty of trailers and never had on without the white ground wire.
Gents - thank you for all the advice and I apologize for not getting back sooner. You nailed it, mrmc.
When I went back to look the next day, I found that the white trailer ground (mounted right to the metal on the tongue) connection was rusted some. It took some grinding with a wire brush but I got the connection good again and the lights to work.
It didn't want to work initially, even with a good bit of grinding, so I think I need to solder it like someone mentioned or work it on a little better somehow or this will happen again in the near future. Even though I keep the trailer in a barn, it's humid as heck down here most days.
Thanks again, all.
thatsmrmastercraft
11-11-2010, 02:31 PM
Glad you got it figured out.