Hi,

We have a '97 E-350 Club Wagon with a 7-pole wiring connector that was added by a shop before we bought it, but as far as I can tell, the wiring under the van is all factory.

The turn signals on the van only light up about half as bright as the brake lights, even though brake and turn use the same bulb/filament. This works fine on the van - the turn signal is still bright enough - but the problem lies in that the trailer lights act the same way. There is not enough difference in brightness between the running lamp and turn signal, so I effectively have no turn signals with the running lights on.

I confirmed that the turn signals were not as bright by putting a voltmeter on the stop lamp/turn signal pins on the trailer light connector. The brake light puts about 10 volts through the circuit, while the turn signal only puts about 6.5 through. I thought it could be a wiring problem, so I checked at the trailer turn signal fuses in the power distribution box under the hood and got the same results.

My question: is this how the lights on the van are supposed to work, or do I have a wiring issue somewhere? If the van is acting normally, are the trailer lights supposed to act the same way, or is there a trailer wiring problem?

Thanks,
Isaac

 

My trailer will blow a 20amp fuse about once a year.Ive had to replace and rewire the male and female trailer plug under the bumper many of times.If you dont use it alot they get all messed up from the elements outside.Sounds like a bad connection in the plug.Inside the plug it tells you witch wire to place in the holes.

 

I did some more checking today with my voltmeter. I pulled a taillight out of the socket and jumpered the flasher to eliminate that as a possible problem, then checked the voltage - 12V for both brake and turn signal at the brake/turn taillight socket. At the brake/turn socket on the trailer connector, I get 12V for brake lights, but only about 9V for turn signal. I did a resistance test between the brake/turn socket on the taillight and the brake/turn socket on the trailer connector and it showed about 5 ohms resistance, which it seems to me would be enough to cause the voltage drop my meter shows. Any bright ideas as to the cause of this problem? I've checked all the connectors I can find and everything seems to be clean and tight.

My other question: does anyone know of a source for a factory service manual for this van, or specifically a schematic of the trailer wiring?

Thanks,
Isaac

 

The cause of a low voltage at the socket is almost always because of a grounding issue. The bulbs are low resistance to begin with so when a low imepedence is introduced through the wiring, the voltage gets lowered. A simple thing to try to confirm this is to add a grounding pigtail to one of the suspect sockets (use one of the solderless splice type connectors and make sure you connect to the ground side). Connect the pigtail to the vehicle frame and then check the voltage. This is especially true for trailer wiring. While energizing one bulb, the current starts to find a path through the other bulb in order to complete the circuit. Sometimes this looks like the blinkers are alternating between the right and left even through only one is energized.