Popping fuses!

Well the fuses taht get blown are the brake/turn/hazards (two, 15 amps).

Here's the problem.. truck works fine when it's by itself. Tried hooking up the trailer to it, and the problem starts when the trailer wire harness is in place. The turn signals would bling quickly 3-5 times then blow out. Same with the brake when pressed.

We tried a new wire harness as mine is a few years old and seen better days.. well it was plugged in upside down (new one), but the blinkers worked. However, if the left blinker was on, the right blinker on the trailer would flash.

I turned the harness upright, and again, fuses blew (either the turnsignal fuse or the brake/hazzard depending on what test method was used).

Anyone have any ideas??

Here's the weird part.. I've towed 3-4 times before and worked fine..until I disconnect the trailers wire harness, then it will pop a fuse. Replace the fuse, then it all works fine..

You may need to re-write this, because it is not immediately clear to me, but my first thought is that the conenctor has some bare wires that short when you have it turned so that it is right side up, but does not short when it is upside down.

Re-wrote it..

The wires look fine however, I can't see much through some 2" holes in that area. What's got me is before when I towed trailers, it would all work fine until I unplug the wire harness..it would instantly pop a fuse, usually the turn signal fuse as that's the first thing I'd use. Replace that fuse, then it would never short out again.

Now it's doing it, but only if plugged in correctly. If harness upside down, it seems to work, but you get the left blinker turns on the right blinker on the trailer..

Is there any way to test with a volt meeter to see what's going on? Where would I test at?

It sounds like some of the wires are backward or it could be a short somewhere...

If it only shorts when the trailer is plugged in, I'd suspect the wiring to and on the tailor. If you have a multimeter use the continuity function. (remove the bulbs so you don't get a back circuit through them) Then use the continuity function to look for a short from the ground lead to one or more of the wires that go to the lamps. You should get no indication, if you do, that is the line that is shorted.

Good luck,

>-

Isn't your trailer connector keyed?

How can you connect it properly, and upside down?

Something is wrong there.

EDIT: Mine looks like this

yo,

Give some more info next time;

how many pins in your connector?

Is it Ford original equipt that came w/a trailer tow option?

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Wiring Diagrams, Haynes for 87-89 Bronco & F series

Source: by equivalent (Beetlejuice) at http://www.supermotors.net/vehicles/registry/7497/31098'>http://www.supermotors.net/vehicles/registry/7497/31098

look at the last one, this one:

http://www.supermotors.net/vehicles/registry/7497/3109

& for the heckuva it;

TSB 89-14-17 Trailer Wiring Colors

Publication Date: JULY 14, 1989

LIGHT TRUCK: 1990 BRONCO, F-150, F-250, F-350

ISSUE: Trailer tow wire harness color codes have been revised to be compatible with SAE color code standards. When hooking up a vehicle to a trailer that has been wired according to the SAE standard, the wire color/circuits will match.

ACTION: Refer to the following Circuit Color Code Chart for the correct color/circuit usage.

CIRCUIT COLOR CODE CHART

CIRCUIT FUNCTION - OLD COLOR* - SAE COLOR*

Trailer LH Turn/Stop - LG/O - Y

Trailer RH Turn/Stop - O/LB - DG

Trailer Brake Lamp From Controller - R/LG - R/LG

Trailer Electric Brakes Solenoid - BL/BR - DB

Trailer Back Up - BK/PK - R/Y

Trailer Ground - W - W

Trailer Running/Tail - W/R - BR/W

Trailer Power (Battery Charge) - Y - O

Trailer Brake Control Feed - R - R

Color Key - Color Abbreviations

BL-Blue

BK-Black

BR-Brown

DB-Dark Blue

DG-Dark Green

LB-Light Blue

LG-Light Green

O-Orange

P-Pink

R-Red

W-White

Y-Yellow

It is a factory plug altho I have a uhaul hitch? Anywho the factory plug is built into the rear bumper.

It's a round plug that plugs into the bumper..you can squeeze it in upside down..weird lol

ok,

like this 7 PIN?????????

http://info.rockauto.com/getimage/getimage.php?imageurl=http%3A%2F%2Finfo.rockauto.com%2FMotorcraft%2Fwpt421.jpg&imagekey=507985-0&width=450

Here is another pic by AARON;

Mine is built into the bumper (left of license plate). Altho my hitch is a uhaul hitch..dunno if it was upgraded or what. I know we had a hitch (or maybe bumper towed?) on it back when I was a young buck..we had a boat in Vancouver and used the Bronco to tow it with..this was back in 90 (truck is an 89). Uhaul hitch sticker doesn't look 20yrs old.. so it has to be an upgraded newer one..

I removed some of the surface rust, and painted it silver..lots of craters tho. It is stamped "FORD" though. It's a four pin.

used to short out the fuse (only once) AFTER you removed the wire harnes/trailer. This time around no wiring has been touched, and it shorts out while trailer is connected. Tried a new wire harness, and it would work when plugged in upside down (left blinker would turn on right blink on trailer), but when pluged in correctly, short out again.

If it shorts AFTER you remove the trailer connector, then the problem is not in the trailer but in the bronco.

I would ground one end of a test light, and turn a directional on, then probe the harness until I get a blinking test light. Then start wiggeling wires until it stops blinking. The short should be near the area that was wiggled.

I'd suspect the socket itself.

What can I say AdamDude04 . Save yourself a lot of trouble and headache. Get a new trailer harness for the truck. Then match that up with a new plug and harness to the trailer. If you have to do any splicing use a weather proof box.

Good luck,

>-

Yeah I'm thinking of just getting an all new four pin connector for the bronco and re-do the wiring harness. Then get a new wire harness.

This one has my head boggled.. the new wire harness would work, but onmly upside down. I would think it would short out regarless if put in correctly or upside down.

Oh joy, what a fun project for I.