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View Full Version : Trailer lights not working...help on adapters


MJDore
05-01-2006, 10:06 AM
The trailer lights on my MC trailer for my 94 205 have never given me problems. I always pulled it with a Yukon using a 7-to-4 adapter that worked fine. Last year, due to a new baby, we only moved the sucker once and now this year I've noticed my trailer lights aren't working. Complicating the investigation into why is the fact that I have a new Nissan Titan doing the towing now so I can't tell if it's the truck or the trailer at fault. I bought a new adapter to rule that out and I decided to buy one of the 'Hoppy' 7-to-4's with the LED indicators on it. These are supposed to tell you whether or not it's a problem with the truck or on the trailer.

When I plug this sucker into the truck the top LED blinks indicating that all is well. When I then plug the trailer into it ALL of the lights blink. I can't understand what this means but all I know is the trailer lights still don't work. I researched Hoppy's website but couldn't find anything. The dealer told me this past Friday that the truck plug is hot. Any ideas or experiences with this sort of thing? Could sitting for a year with little or no use have an affect on the lights? It's been in dry storage so I don't see how it could. Any experience with these types of adapters?

Thanks....

erkoehler
05-01-2006, 10:40 AM
Do you have any corrsion on the trailer plug?

Kevin 89MC
05-01-2006, 10:54 AM
Do you have a voltmeter? If not you can get a multi-tester & they come in handy for troubleshooting home & vehicle wiring issues. I'd just test for voltage at the end of the adapter for the various light conditions. If those are OK, then check for voltage at the lights. If you have the tail lights that plug in to a harness, just unplug them & check there. Otherwise open up the crimp connectors & check there.
Good luck.

Tom023
05-01-2006, 11:23 AM
I would also double check the ground wire coming out of the trailer side connector, making sure it has a good trailer ground. Technically grounding can occur through the hitch, but having a good ground wire through the connector is required. I've seen several problems due to bad grounds.

87 TriStar 190
05-09-2006, 10:41 PM
I agree with Tom03. It's probably a ground issue. If you just hooked it up and tried the lights, it's not a surprise it won't work. Take it for a drive making several good turns to take any corrosion off the hitch ball andf socket. Also make sure your trailer ground wire is connected to a nice metal surface with no corrosion. Try another trailer with known good lights to simply verify the new tow vehicle. It'll probably be something simple. I'd try the drive first and then check your lights. Good luck.

Leroy
05-10-2006, 12:19 AM
Agree with Kevin, the VOM is your friend. Start checking voltages from truck plug back.

Bert
05-10-2006, 12:51 AM
Agree with Kevin, the VOM is your friend. Start checking voltages from truck plug back.

Make sure the ground is good as mentioned. High impedence ground connections are often the culprit. Grounding through the hitch is a poor practice. Checking with a voltmeter will find the problem.

Leroy
05-10-2006, 07:25 AM
You are correct Bert and you can find the poor ground problems by measuring with the VOM also across the grounds. Good ground then you willl be zero to few tenth's of a volt, bad ground will be few tenths of a volt to 13.8 volts. In other words the voltage is across the ground instead of the bulbs.

Make sure the ground is good as mentioned. High impedence ground connections are often the culprit. Grounding through the hitch is a poor practice. Checking with a voltmeter will find the problem.

Workin' 4 Toys
05-10-2006, 08:37 AM
When I then plug the trailer into it ALL of the lights blink.
Please clarify, is "it" the tester, or the truck?

atlfootr
05-10-2006, 09:07 AM
Do you have a voltmeter? If not you can get a multi-tester & they come in handy for troubleshooting home & vehicle wiring issues. I'd just test for voltage at the end of the adapter for the various light conditions. If those are OK, then check for voltage at the lights. If you have the tail lights that plug in to a harness, just unplug them & check there. Otherwise open up the crimp connectors & check there.
Good luck.After performing all the above and problem still exist, swing into a trailer / utility shop (U-Haul) there great ppl to use for trouble shoot'n problems like this. Charge is usually 25- 30 bucks to fix it. :twocents:

Workin' 4 Toys
05-10-2006, 09:12 AM
Correct me if I am wrong, but shouldn't there already be a ground wire in the 4 wire plug. Maybe it isn't connected at the truck side. I am confused by the blinking light comment in his testing, not sure if it was the trailer blinking or the tester.
Either way, take a baking soda/water mix and clean the plugs on both the truck and trailer, then rinse with water. Repeat as needed, this should clear out most of the corrosion if any. But I blame the connectors.
Has the new truck ever been hooked up to a trailer before?

MJDore
06-04-2006, 09:56 PM
The flat-4 wire from the trailer to the truck adapter was the culprit. After inspecting it a couple of weeks back I noticed it was in pretty rough shape. It was grounded to a screw on the trailer albeit not very well.

I ended up buying a new flat-4 wire (one that was a foot longer) that has the ground wire included in the plug and all is well now! :steering:

Thanks, guys.

NatesGr8
06-05-2006, 09:04 AM
just saw this post, glad you got it fixed. i have the same setup with the titan. I use the coiled wire 7 to 4 adapter. Its like a 2 foot extension. Just redid all the lights the beginning of this season and i love having all the lights working. Even more so now that they're all LED's :D

MJDore
06-05-2006, 10:59 AM
just saw this post, glad you got it fixed. i have the same setup with the titan. I use the coiled wire 7 to 4 adapter. Its like a 2 foot extension. Just redid all the lights the beginning of this season and i love having all the lights working. Even more so now that they're all LED's :D

The Titan is a beast, huh? Makes for a smooth pull through the hills in TN. LOVE IT.

NatesGr8
06-05-2006, 01:23 PM
yeah, i love it. i'm so glad we have the titan. couldn't imagine towing with anything else :headbang: