Tow vehicle to trailer connection help needed.

[Mercy]

I have a 2003 Excursion I use to tow about everything. It has a 7 and 4 pin, and I used it 2 weeks ago (7pin) with no issues. My dad used it to haul the rhino somewhere last week with a 4pin and parked it. I asked them to bring it down (from our farm) with the 4pin trailer and my dad tells me the 4pin isn't working. Now I am guessing my dad knew it wasn't working and drove it anyway because he sure started working on it the instant my mom said they were driving it down.

I told them just to bring the truck, leave the trailer. I suspect it's the trailer that has an issue. How can I test the 4 pin to see if it's working? I am pretty much on my own diagnosing and fixing it and the trailer is going to be 250 miles away so I can't look at it or try to hook it up for a couple weeks.

[redcorvetteman3]

http://www.amazon.com/Seachoice-1391.../dp/B000N9MFJC

[Mercy]

Thank you!

[dirttracker18]

If you have a multi meter, or can borrow one just ground to the hitch and check for power. A online search will give you what wire should be what. One is a ground, check that too.

A simple test light will work too. You could make a crude one with a bulb and some wire.

No need to order a tester you can only use on a 4 point connection.

A multi meter can be had inexpensively and is a must have tool anyway.

[dirttracker18]

FWIW I have an 04 F150 that the 4 pin quit working on too. I have a 7 to 4 pin adapter so just use that.

[Lotek]

Originally Posted by dirttracker18

If you have a multi meter, or can borrow one just ground to the hitch and check for power. A online search will give you what wire should be what. One is a ground, check that too.

A simple test light will work too. You could make a crude one with a bulb and some wire.

No need to order a tester you can only use on a 4 point connection.

A multi meter can be had inexpensively and is a must have tool anyway.

Use a testlight, a multimeter won't tell you if the circuit will flow enough current to light the bulbs, in fact an 1157 with a couple of leads attached is my preferred tool for this app.

[Mercy]

I grabbed a 4pin tester at HF for $4, and a 7 to 4pin just in case. I have a multi-meter, but I don't think I have a test light. I'll probably grab one just to learn how to use it. Thanks again! Hopefully it will work and it's the trailer.

[theoldwizard1]

All Ford's I have seen with separate trailer wiring have separate fuses for those circuits.

[Mercy]

Originally Posted by theoldwizard1

All Ford's I have seen with separate trailer wiring have separate fuses for those circuits.

It should be here in an hour or so. I'll check that too, thanks.

[xtremek]

Originally Posted by Mercy

I grabbed a 4pin tester at HF for $4, and a 7 to 4pin just in case. I have a multi-meter, but I don't think I have a test light. I'll probably grab one just to learn how to use it. Thanks again! Hopefully it will work and it's the trailer.

I'd use a multimeter. Use the hitch as a ground. With the right turn sig on you should see close to the same voltage you see on the battery on the green wire. With the left on, you should see the same on the yellow wire and with the tail lights on you see the same on the brown. Then turn everything off and switch it to the ohm setting. You should see less than 1 ohm from the white wire to the hitch(it may take some wiggling to get a good ground on the hitch). If you use a test light, the light should be on during the same situations as above, but you won't be able to check the quality of the ground. If you want to check the 7 pin, Etrailer.com has a nice breakdown.

[Lotek]

Originally Posted by xtremek

I'd use a multimeter. Use the hitch as a ground. With the right turn sig on you should see close to the same voltage you see on the battery on the green wire. With the left on, you should see the same on the yellow wire and with the tail lights on you see the same on the brown. Then turn everything off and switch it to the ohm setting. You should see less than 1 ohm from the white wire to the hitch(it may take some wiggling to get a good ground on the hitch). If you use a test light, the light should be on during the same situations as above, but you won't be able to check the quality of the ground. If you want to check the 7 pin, Etrailer.com has a nice breakdown.

Think this one through, you want to check a circuit that has to drive a light bulb, usually an 1157, a multimeter would tell you that you have 12 volts even if there was a mostly broken wire with just one strand making the circuit. That one strand will not power a tail light. If you hook your test light to it, you will get a dim glow at best, problem found. To test ground, hook the test light to the positive battery cable instead of ground. Using an ohmmeter can bite you in the butt as well, some times you need to check the ground under load to get a fault to occur, you can use the voltmeter to check voltage drop on the ground circuit, but a homemade testlight with an 1157 bulb will test the entire circuit at once.

DON'T use the 1157 testlight on any other ckt without verifying first that the ckt can handle the load.

[signcrafter]

Originally Posted by Lotek

Think this one through, you want to check a circuit that has to drive a light bulb, usually an 1157, a multimeter would tell you that you have 12 volts even if there was a mostly broken wire with just one strand making the circuit. That one strand will not power a tail light. If you hook your test light to it, you will get a dim glow at best, problem found. To test ground, hook the test light to the positive battery cable instead of ground. Using an ohmmeter can bite you in the butt as well, some times you need to check the ground under load to get a fault to occur, you can use the voltmeter to check voltage drop on the ground circuit, but a homemade testlight with an 1157 bulb will test the entire circuit at once.

DON'T use the 1157 testlight on any other ckt without verifying first that the ckt can handle the load.

I bought this a while ago to solve this problem, http://www.amazon.com/Electronic-Spe.../dp/B004IKPUL2.

[Lotek]

Originally Posted by signcrafter

I bought this a while ago to solve this problem, http://www.amazon.com/Electronic-Spe.../dp/B004IKPUL2.

I have that too, but it's overkill for this application.

[signcrafter]

Originally Posted by Lotek

I have that too, but it's overkill for this application.

True it's not worth it for one time use. But it's nice to have around to eliminate what you were talking about. I was stumped many times when the fluke told me I had battery voltage but the light still wouldn't work. Now I just keep these leads on the fluke almost all the time and can eliminate any resistance issues with a push of a button. Just an option for the OP if he thinks it will come in handy in the future.

[jhelrey]

Fix it yet?

[TimeWarpF100]

Originally Posted by Mercy

I have a 2003 Excursion I use to tow about everything. It has a 7 and 4 pin, and I used it 2 weeks ago (7pin) with no issues. My dad used it to haul the rhino somewhere last week with a 4pin and parked it. I asked them to bring it down (from our farm) with the 4pin trailer and my dad tells me the 4pin isn't working. Now I am guessing my dad knew it wasn't working and drove it anyway because he sure started working on it the instant my mom said they were driving it down.

I told them just to bring the truck, leave the trailer. I suspect it's the trailer that has an issue. How can I test the 4 pin to see if it's working? I am pretty much on my own diagnosing and fixing it and the trailer is going to be 250 miles away so I can't look at it or try to hook it up for a couple weeks.

Your local parts house should have a circuit tester like this one: 5~10.00
Hook the clip end to ground and the 4pin connector if vertical the top one will be for rh turn/stop/hazard (end female)
2nd one down is for LH Stop, Hazard (2nd Female)
3rd one down is for Parking / Taillight (3rd Female)

There are 3 female connectors and 1 male

The end female is RH Stop/Turn
2nd LH
3rd Parking/Tail

If no power at any of those three key on foot on brake, or hazards on the fuse is most likely blown.



Power distribution box under hood. #4 is for Trailer tow backup and trailer tow park lamps it is a 20A fuse. Underhood Fuse #20 is a 7.5A Trailer Tow Stop and LH Turn. #22 is for trailer tow stop and RH Turn also a 7.5A. If you have power to those 3 terminals at 4 pin connector your trailer wiring is faulty.



The high-current fuses are coded as follows.
Fuse/Relay
Location
Fuse Amp
Rating
Power Distribution Box Description
1 20A* Rear Wiper
2 — Not Used
3 15A* Quarter Flip Window Motor
4 20A* Trailer Tow Backup Lamps, Trailer Tow
Park Lamps
5 20A* Instrument Panel Auxiliary Power Point
6 10A* Gasoline only-A/C (CASS)
Diesel only-Alternator A Field
7 20A* Floor Console Auxiliary Power Point
8 15A* Park Lamps
9 20A* Left Rear Quarter Auxiliary Power Point
10 30A* Head Lamps
11 20A* Cargo Auxiliary Power Point
12 15A* DRL, Fog Lamp Relay
13 10A* Washer
14 15A* Horn
15 5A* Fog Lamps
16 — Not Used
Roadside emergencies
155

Fuse/Relay
Location
Fuse Amp
Rating
Power Distribution Box Description
17 — Not Used
18 — Not Used
19 20A*
(Gasoline
only)
— (Diesel
only)
Gasoline only-E40D/HEGO
Diesel only-Not Used
20 7.5A* Trailer Tow Stop /Turn LH
21 10A* Left Headlamp
22 7.5A* Trailer Tow Stop /Turn RH
23 10A* Right Headlamp
24 20A*
(Gasoline
only)
— (Diesel
only)
Gasoline only-Engine Control
Diesel only-Not Used
101 50A** Ignition Switch (B1 & B3)
102 30A** Power Door Locks
103 40A** Auxiliary Blower
104 30A** Electronic Shift On The Fly (Transfer Case
Motor)
105 50A** Junction Box Battery Feed
106 — (Gasoline
only)
30A**
(Diesel
only)
Gasoline only-Not Used
Diesel only-Injector Driver Module
107 30A** Heated Seats
108 30A** Power Seats, Adjustable Pedals
109 40A** Front Blower Motor
110 30A** Trailer Tow Electronic Brake
111 — Not Used
112 20A** Fuel Pump

[TimeWarpF100]

These are for fuse panel above your feet (under column inside)

The fuses are coded as follows.
Fuse/Relay
Location
Fuse Amp
Rating
Passenger Compartment
Fuse Panel Description
1 20A Radio, Secondary Fusing for Audio Options
2 5A Instrument Cluster, Powertrain Control
Module (PCM) Keep Alive Memory, PATS
LED
3 20A Cigar Lighter, Data Link Connector
4 — Not Used
5 — Not Used
6 — Not Used
7 5A Power Window/Lock Switch Illumination
8 5A Headlamp Switch, LED/Radio
9 — Not Used
10 — Not Used
11 30A Wiper Run/Park Relay Coil, Wiper Hi/LO
Relay Coil, Washer Pump Relay Coils, Front
Wiper Motor, Rear Wiper Motor Relay Coils
12 — Not Used
13 20A Stop Lamps, Center High-mount Stop
Lamp/Hazard, Trailer Tow Stop Lamp,
Speed Control
14 15A Dome Lamp, Cargo Lamp, Courtesy Lamps,
Running Boards, Power Mirrors, Vanity
Mirrors, Map Lamps, Underhood Lamps,
Glove Box Lamp, Power Windows (Delayed
Accessory)
15 5A Stop Lamp Switch (Logic), PATS, GEM
16 15A Hi-beam Headlamps, Instrument Cluster
(Hi-beam Indicator)
17 — Not Used
18 10A Rear Integrated Control Panel (RICP), CD
Changer
19 10A Instrument Cluster, GEM Module, Overdrive
Cancel Switch, PATS/PATS Transiever, Idle
Validation Switch (Diesel only)
Roadside emergencies
152
Fuse/Relay
Location
Fuse Amp
Rating
Passenger Compartment
Fuse Panel Description
20 15A Starter Motor Relay, GEM
21 5A Radio Start Feed
22 10A Blower Motor Relay Coil
23 10A Air Bag Module
24 10A A/C Clutch, Blend Door Actuator, Trailer
Tow Battery Charge Relay Coil, Rear
Defroster
25 5A 4-Wheel Anti-Lock Brake System (4WABS)
26 — Not Used
27 10A Ignition Run Power Feed (Customer
Access)
28 15A DRL, Brake Shift Interlock (BSI), ECM,
Overhead Trip Computer (OTC), AUX A/C
Components, Hazard Flasher, Speed
Control, Vacuum Pump, Backup Lamps,
Electronic Shift On The Fly Hublock
Solenoid, Heated Seat
29 5A Instrument Cluster (Charge and Airbag
Warning Lamps)
30 30A PCM Relay Coil, Ignition Coil (Gasoline
only), Fuel Heater (Diesel only), Wastegate
Solenoid (Diesel only), Injector Driver
Module Relay Coil (Diesel only)
31 15A Heated Mirrors, Rear Defroster ON
indicator
Relay 1 — Interior Lamp Relay
Relay 2 — Battery Saver Relay
Relay 3 — Horn Relay
Relay 4 — Power Window One Touch Down Relay
Relay 5 — Accessory Delay Relay
Roadside emergencies

[Mercy]

I am only getting power to the right and left not tail. I do have a brake controller hooked-up under the steering wheel so I will check that and the fuses and see if I can find the problem.

[Mercy]

OK, my fuses don't line-up with your numbers. I am going with the manual and checking everything that says trailer after the number.

[Mercy]

It's not the fuses. I checked what I could see of the wiring but then it goes under a skid plate and disappears.