I have a 1990 Ford 15 passenger van with the 5.7 L engine. I am pretty sure it is a E350 but I am not 100% on that. So, here is the problem. The van is used to tow a trailer. However, the trailer has been ruled out for this problem as we disconnected it, and the problem still happened.

When you turn on the ignition, the fuse for the Turn Signals blows. It does not matter if the turn signal switch is on left turn right turn or off. It blows the fuse. It is not the turn signal switch, because I disconnected the switch and the fuse still blows. The emergency flashers work. The brake lights work. The running lights work. The headlights work. I replaced the turn signal relay, to no avail.

I called my mechanic and read him off what was on the circuit supposedly.

Turn Signals, back up lamps, dual battery relay coil, DRL module, HEGO.

The mechanic said to try unplugging the O2 sensor because it has a coil in it, I did, to no avail.

The van only has a single battery, so there is no dual battery relay coil.

I am 90% sure the van does not have (DRL) Daytime Running Lights.

So, I am at a loss. I have an appointment with the mechanic in a week, but I was really hoping that someone would have an idea. I am sure it will be expensive to fix with the mechanic as he did not have any idea what else might be wrong with it.

PLEASE HELP!

Thanks!

Joe

 

Your back-up lamps switch is usually on the side of the tranny. The wiring going down to this area is particularly prone to getting against exhaust pipes and getting hung up in the linkage. If you see a harness going that direction, from the firewall to behind the engine, see if it's damaged or laying against the exhaust.

 

With the fuse blowing as soon as the switch is turned on it is a short circuit. As Franklin2 says you need to check your wiring for a burned or pinched wire.

 

So, I followed Franklin's idea and checked out the wire between the tranny and the wiring harness, it is fine. I even went so far as to pull of the engine shroud (for lack of a better term) and unplug those wires from the wiring harness, to no avail.

Any other ideas? I know it is a short somewhere, but there is no way to go look through the entire wiring harness to check. It also seems strange that if there was something that would cause a short in the wiring harness no one else has had this problem. That is what makes me think it is something that went bad and shorted.

Ideas?

 

By chance does the van have tilt steering? When you disconnected the switch, exactly where did you unplug the wires? See where I'm going with this?
AL.

 

No, it does not have tilt steering. At the base of the steering column there is a plug that is shaped like a 1/4 of a circle. This is where I unplugged the turn signal switch. I found that switch, of course, after I had dismantled the entire steering column.

Joe

 

I have the exact same problem. Did you find the solution? Please email me at mcjksmith@comcast.net

 

I had the exact symtoms. It turned out to be the Oxygen sensor wire. I have a 1990 E350 w/460 Jamboree Motorhome. The wires had melted together over time. Be sure to make sure the wire shielding is covering the wire near the sensor and tied off away from the exhaust.