tow hitch electric problem

jmgasior

jmgasior
bought a 08 2500 and had them put a hitch on,a 7 pin.u-haul did it for them,brouhght it home and hooked to tent trailer and nothing,measured at the plug and .2 of a volt although wired correctly as I can see brake lights,directional etc.at the right pins went back and they
put on a light tester and looked ok,but I said what are the voltages,they said lite comes on and I'm ok story,also said I had to be hooked up as I needed the vans ground,mentioned not the case on my tow vehicle.finally they hooked it up to one of their trailers and it worked but the trailer was a 4 pin so he used a adapter,now I'm thinking its me,went home hooked it up and nothing,check my wiring again and everthing is the same.
they did their connection in the left tailight.Read earlier that there may be more involved although nobody wants to hear it.need some HELP to prove my case,thanks in advance,guys
 

bikergar

Active member
If you have the meter to a good ground it should be reading near 12 volts. Also check the ground on your pop up.

gary
 

jmgasior

jmgasior
sorry the trailer works fine with my old tow vehicle,I beleive the fact that I'm not getting the proper voltage fron the sprinter is the problem,lets put our heads together and get me straightened out,thanks
 

bikergar

Active member
.2 volts won't light the tester. Have you checked the grounds. Hook your meter to a known good ground on the Sprinter.
 

folzag

Member
You can also do a continuity check between the ground on the vehicle connector and the vehicle chassis.

I presume the 0.2 volts you've measured is between the connector's ground pin and the signal pins? It sounds like the connector ground is floating. If the tester light was connected to the chassis, that would provide the ground path that allows it to work while the trailer would not. With your trailer connected, run a jumper wire from the harness' ground wire to the chassis. If your connector ground is floating, the jumper would allow the trailer lights work.
 

folzag

Member
One more thing... you said the trailer works fine with your old tow vehicle. When exactly was that?

Also, two wrongs sometimes make a right. If your old tow vehicle crossed some pins and your trailer harness uncrossed them, that would explain why the trailer works with one vehicle, but not another. Anyway, just throwing out ideas... be careful what you trust to be right.
 

jmgasior

jmgasior
the tow vehicle worked ok today,the wiring is straight to the right pins,I carefully checked that,I need to make sure of the ground situation.does anyone have a hitch with a 7 pin connecor and was it just a conventional wiring to the tail-light or does it get more complicated because its a sprinter?thanks for all the thoughts.
 

glntom

New member
I would still hold out for a bad ground, run a jumper wire to ground trailer to KNOWN good ground on sprinter. With all the undercoating, etc I could easily believe no grounding through the hitch.
 

bikergar

Active member
Does your tent trailer have separate tail, brake, and turn bulbs? If it doesn't you need a tail light converter to make it work.

gary
 
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bikergar

Active member
hi, have only 1 bulb for all applications,where does this adapter hook into the cht?thanks
That would be your problem then...:cheers:

Do you anticipate towing anything that has separate bulbs? If no you could install it just prior to the plug on your towing vehicle. If yes install it just after the plug on the camper. You could also make a pigtail with the converter in the middle.

gary
 

jmgasior

jmgasior
got a day off,and checked the ground,and the grd pin at the plug has continuity to the frame grd,a question for bikergar abt the bulbs,being it works ok with my van i crawled underneith and cant find anything outside of the normal wiring,have a call into the installer who installed the plug on my old van to see if he added anything,thanks for the help but still need somemore to get this working,thanks,againmy old van has a brake controller and the new van doesn,t could this be part of the problem?
 

jmgasior

jmgasior
not quite sure what you mean,on the old van brake and turns are on seperate fuses,on the new one cant even find turn signals but I see the brake fuses show nothing else with it.is this what you are looking for?really appreciate your help.
 

famof8

Famof8 + 1 = Famof9!
When U-Haul made the connections in the taillight, they should have installed a taillight converter. It will be a small black box about the size of a deck of cards. On the vehicle side there will be a ground wire, a left turn signal wire, a right turn signal wire, a brake light wire, and a tail (running) light wire. On the trailer side will be five wires which may lead directly to a 4-pin plug: Yellow - left turn and brake; green - right turn and brake; brown - taillights; and white - ground. It may be installed behind the lens assembly or it may be under the vehicle. In addition, your 7-pin plug will have a wire that runs to the front of the vehicle and connects to the battery. It will be connected to the Black wire on the 7-pin. The blue wire on the 7-pin will go to the brake controller and the purple wire will go to the reverse light wire on the taillight harness. Depending on the number of marker lamps on your trailer, the draw may be too much for an unpowered taillight converter. If U-Haul did it right, they should have installed a powered taillight converter (my opinion, but necessary for high draw circuits - my trailer draws 6 amps on the marker circuit which is too high for an unpowered unit). If it is a powered unit it will also have a battery wire from the taillight converter to the battery as well. Look under your hood and see if they installed a fuse holder to the battery. They should also have installed a 40 amp circuit breaker for the battery wire on the 7-pin connector.

To test, use a meter on the 4-pin plug. Turn on your headlights. Put the negative lead on the meter to the white ground pin on the 4-pin. Put the positive lead to the brown taillight pin on the 4-pin. If your van's lights are on, then there should be 12 volts there. You can test this same theory by repeating this test at any bulb on the trailer after you have tested the van. Place the negative lead on the trailer frame and the positive lead to the incoming bulb stud on the trailer light. You should have 12 volts there as well. If not, then one of two things is happening. Either your trailer ground is no good (probably not the case since your other vehicle makes it work) or the van's light circuit doesn't have enough umph to power the trailer lights. Also... check the ground connection on the 7-pin to make sure that it is connected tot he vehicle. Place your meter on ohms or continuity and place one lead on the truck frame to bare metal and the other lead on the bottom left (looking into the plug) tab of the 7-pin. The resistance should read less than 3 ohms. If not, then that would explain why the trailer lights do not work and would explain why the 4-pin connector does.

Let us know what you find.
 

jmgasior

jmgasior
next dry day will get back under there,i see a small black box in the lens and a black wire going into the lens from the front of the van,so i might assume i have a powered convertor,but there is no 12 v at the bumper plug.{the top right blade looking into it} i do have many marker lites so i will look for 12v there,have a good ground from the plug to the new vans frame.any idea how to get the tail light lens off so i can see what they did in there,thanks again,will report back.thanks for everyones patience.
 

famof8

Famof8 + 1 = Famof9!
next dry day will get back under there,i see a small black box in the lens and a black wire going into the lens from the front of the van,so i might assume i have a powered convertor,but there is no 12 v at the bumper plug.{the top right blade looking into it} i do have many marker lites so i will look for 12v there,have a good ground from the plug to the new vans frame.any idea how to get the tail light lens off so i can see what they did in there,thanks again,will report back.thanks for everyones patience.
Is the ground that you see for the 4-pin or the 7-pin or have you traced one for both?
 

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