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Premium 4 Lyfe - Way Back Staff
'95 XLT: 5.8, MAF, E4OD, 4.56's, 6" lift on 33's
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Discussion Starter #1
So after re-wiring a complete trailer I frustratingly realized that my oem installed 7-blade trailer plug wasn't working right anymore. I'm unsure if the '95 came with a trailer tow package or not, but I don't think so. There's no trailer brakes installed and never have been, near as I can tell but the trailer hitch is well installed (possibly factory?) and it had the 7-blade plug-in, complete with the Ford logo.

I searched our site and the web and found a simple diagram of the connector elsewhere. Everything around here ended up with no decent details, just simple conversations with a few suggestions but no tech. details. Pulled out my paperback EVTM and wondered through that until my eyes glazed over and my brain went numb. Try as I might, I still don't "speak" electrical.

Got out my test light and spent a lot of time manually testing it by myself. The Ford plug-in blades have a lot of corrosion but I could get a connection from my 7-4 test adapter, if I push it in snug and pull it out just a bit. After many back and forths, the ONLY thing I could get any light from was for the left turn/brake signal and a solid ground. No right side blink/brake and then I found that some p.o. had bypassed the malfunctioning running lights wire with a hotwire tied in somewhere to the left side harness heading to the left side tail-light. Probably a shop job, as it was fairly well done but the 2 connectors to the 7-blade plug-in were left dangling right behind the fuel tank. As such, over time a lot of dirt/mud had worked into those 2 connectors.

So I pulled those connectors apart and started testing them directly... all over again. The black connector holds the 4 wires for ground (white, thick gauge), the left blink/brake (green), the right blink/brake (yellow) and the running lights (brown/white). The gray connector holds the 3, aux. power, e-brake and back-up wires, all thick gauge. The gray, heavy duty plug gave me no reaction at all. I didn't expect the e-brake but thought maybe the aux. power might be live. It's not but I might not know what to turn on for it. Then I checked the black, light duty plug and got the exact same reaction as I did testing the 7-blade plug-in directly. ONLY the left side blinker/brake works at the connector.

The oem plug is hard to find and expensive when they have one in stock... but I couldn't find on in stock anyway. So I ran to the local O'Really's and picked up a Hopkins 7 & 4 plug-in. It's wired for plug-play with the newer rigs but I figured I'd have to bypass the bad connectors anyway and while I still want to keep the 7-blade plug option, I haul a few different trailers with 4 prong connectors all the time.

I also picked up a few shrink-wrap butt connectors, some e-tape and a few misc. while I was there. I got back home and clipped off the black connector tight against the backside. I tested the wires again, to make sure the issue wasn't just in the connectors that had been exposed to on and off-road grime/dirt/mud. Exactly the same results with no power coming from the running lights or the right side blink/brake wires.

So... my big problem now is, I think I'm going to have to either drop the fuel tank to get into the actual harness and find/fix the problem with the wires, or I'll have to do a craptastic patch job using the lights going to the wires themselves and bypass the proper harness. I'm not a fan of craptastic work and experience has shown me that patch-work jobs rarely last longer than a few years, especially if a rig gets well used.

I'm pretty sure it's not a fuse problem because a p.o. had bypassed the faulty running light wire before and the left blink/brake is still working. All the lights on the truck itself work just fine and operate as they should.

I'm also considering if I should blow off the whole 7-blade plug-in and just patch in a simple 4 prong and return the Hopkins combo plug or if I should drill a hole in the OEM bumper and install the Hopkins combo straight onto the OEM bumper. I hate the way the oem plug setup hangs down on it's mounting plate, below the hitch... just waiting to get snagged on something when I'm off-road but I'm hesitant to drill into the bumper and mess up the chrome finish.


Has anyone had a problem in the past with the wiring to the oem 7-blade plug-in? If so, do you remember where the wiring went bad? Everything is in the wire loom, as it should be but obviously I'm loosing connection somewhere in the line to 2 of the 4 wires for the black, light duty connector and I get nothing at all from the 3 wire, gray, heavy duty connector (still attached) that I know absolutely nothing about. I hate the idea of dropping the tank, with all the connections and potential to cause other problems involved. So much so, that I made the fuel tank access panel in my last FSB to avoid it.

I'm also curious if anyone has drilled into the face of the oem bumper and if they later regretted it from chrome peeling or other problems. If I go that route, it will be a real tight fit to get my hands in there and seal with weather shrink butt-connections, especially without dropping the tank.

As always, thanks in advance for any help.
 

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Ford Hoarder
78 & 92
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6,715 Posts
I have had this issue 1 time on a 96 250 (pre-wired from factory) On that truck my issue was right where the cab and bed meets. Kink in wire insulation led to corrosion of wire itself.
I ended up running all new wire from about the fuel filter back. I was able to get some of the 7 way wire, locally by the foot, though I do not remember where.
Seems these wires are bad about getting spots in them, especially if they have been tapped into for anything else.

I had a '92 f-150 that had similar issues. Being that truck was near end of life rusty for me. I used one of these https://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Ford/Bronco/1993/HM40435.html?VehicleID=19931171804 then just ran new wire for the electric brake. Granted this did not really fix the other wiring just got me a use-able plug.
 

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Super Moderator
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24,686 Posts
Yo Pepe`,

Section 18-01: Wiring and Circuit Protection1996 F-150, F-250, F-350, F-Super Duty Chassis Cab, Motorhome Chassis, and Bronco Workshop Manual
DIAGNOSIS AND TESTING
Electrical Schematics, Trailer Towing Package Wiring
Trailer Tow

159831





Multi-Function Switch
159832




Trailer Adapter Connector
159833


Pin NumberCircuitCircuit Function
1963 (BK/LB)Trailer Backup Lamps
249 (O)Trailer Battery Charge
364 (DG)Trailer RH Turn Signal
443 (DB)Trailer Brakes
5206 (W)Trailer Ground
652 (Y)Trailer LH Turn Signal
7962 (BR/W)Trailer Running Lamps



Relay Connectors
159834


[
Pin NumberCircuitCircuit Function
86298 (P/O)Fuse to Relay Coil
8737 (Y)Fuse to Relay Switch
87aNot Used
3049 (O)Relay Switch to Trailer Battery Charge
8557 (BK)Ground

Pin NumberCircuitCircuit Function
86140 (BK/PK)Backup Lamps to Relay Coil
8737 (Y)Fuse to Relay Switch
87aNot Used
30963 (R/Y)Relay Switch to Trailer Backup Lamps
8557 (BK)Ground
■○■¤⊙¤
In following, I added narrative in quotation marks to save you from clicking on subject to read each.
Section 18-01:
Wiring and Circuit Protection

DESCRIPTION AND OPERATION
Fuse Junction Panel
Power Distribution Box
Fuse Links
Fuses and Circuit Breakers
Wire Color Code
Trailer Towing Package Wiring
DIAGNOSIS AND TESTING
Electrical Schematics, Trailer Towing Package Wiring
Inspection and Verification, Trailer Towing Package Wiring;
"Check the trailer feed wiring (13A576) and the added trailer connector for obvious signs of damage.
Check fuses for damage.
If the concern remains after these checks proceed to the following symptom chart."

Symptom Chart, Trailer Towing Package Wiring;
"...
  • Trailer Lamps Inoperative
  • Fuse.
  • Rear lamp wiring.
  • Trailer feed wiring.
  • Trailer wiring or bulbs.
  • Trailer Stop, Turn or Hazard Lamps Inoperative
  • Fuse.
  • Rear lamp wiring.
  • Trailer feed wiring.
  • Trailer wiring or bulbs.
  • Trailer Tail Lamp and Running Lamps Inoperative
  • Fuse.
  • Rear lamp wiring.
  • Trailer feed wiring.
  • Trailer wiring or bulbs.
  • Trailer Battery Charging Inoperative
  • Fuse.
  • Rear lamp wiring.
  • Trailer feed wiring.
  • Trailer Electric Brakes Inoperative
  • Fuse.
  • Rear lamp wiring.
  • Trailer feed wiring.
  • Trailer wiring or bulbs.
  • Single Trailer Lamp Inoperative
  • Trailer wiring or bulbs.
  • Have trailer serviced by an authorized camper/trailer repair center.
..."

Pinpoint Tests, Trailer Towing Package Wiring;
"Detailed tests!"
Component Test, Trailer Towing Package Wiring;
"Backup Lamp Relay
Testing of an ISO relay can be accomplished through the use of three No. 10 (or larger gauge) jumper wires and a Rotunda 73 Digital Multimeter 105-R0051 or equivalent. Remove (unplug) the relay to be tested from the power distribution box, fuse junction panel or individual connector. Using the multimeter, check for continuity between terminal 85 and all other terminals. If resistance is 5 ohms or less between terminal 85 and any other terminal, replace the relay. If resistances are greater than 5 ohms, continue with test.
Using two jumper wires, connect relay terminals 86 and 30 directly to the positive battery terminal. Using the multimeter set in the volts position, check for voltage at terminal 87. If battery voltage is not indicated, replace the relay. If battery voltage is indicated, connect a third jumper wire to terminal 85 and ground the jumper wire to a known good ground. Check for voltage at terminal 87A. If battery voltage is not indicated, replace the relay."

REMOVAL AND INSTALLATION
Fuse Junction Panel Cover, Instrument Panel
Power Distribution Box Cover
Fuses, Relays or Circuit Breakers
Wiring Harnesses
SERVICE PROCEDURES
Wire Terminals
Connectors, In-Line, Blade Type
Fuse Link and Butt Connector Service
 

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Premium 4 Lyfe - Way Back Staff
'95 XLT: 5.8, MAF, E4OD, 4.56's, 6" lift on 33's
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35,881 Posts
Discussion Starter #4
Awesome info guys. I'll be digging in later today, so I'll pull this up again out in the shop and start digging through. Thank you both so very much!
 

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Premium 4 Lyfe - Way Back Staff
'95 XLT: 5.8, MAF, E4OD, 4.56's, 6" lift on 33's
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Discussion Starter #5
Well... I got it worked out today. After checking and chewing and checking some more, I decided to just suck it up and patch work the 4-way plug in alone. It's my only rig and I just didn't want to suffer the downtime of dropping the tank and digging in deep right now. I'd like the 7-blade but I honestly don't have any need for it (until I say that. haha). I cleaned things up and left the option available for the future but to get back in that harness and do it right, I really need to drop the fuel tank to access the harness. When I installed the relay upgrade to my tailgate window, I followed that harness from stem to stern routing my fresh power supply wire alongside it and the only place I couldn't run right alongside it and see that it was all good, was on the side of the fuel tank... so whatever problem I've got, it HAS to be in that area because everything else looks perfectly fine. Since I know that sooner or later, my fuel pump will give out and because I have so much semi-permanently setup in the back (speaker box, platform, etc.) of my rig, I'll need to drop the tank anyway. So... I kept the multi-plug around and when it happens, I'll deal with both the fuel pump and the 7-4 multi-plug setup then.

FWIW, I tested all 3 of my trailers and 2 out of 3 worked perfectly and my tiniest tilt trailer likely needs some fresh bulbs but it sits so low, the rigs light are visible anyway.

Thanks again guys! (y) 🍻
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
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I'm also curious if anyone has drilled into the face of the oem bumper and if they later regretted it from chrome peeling or other problems.
I did this on my 90. I don't seem to have any pics loaded, so I'll have to get a shot later. The height of the plug was about the same as the rubber moulding. I cut a section of moulding out & drilled it to mount there. The plug assembly is black, so it blends in pretty well. It's a nice solid mount & well protected up there. The only thing I wish I'd done differently would have been to use that combo 7 blade / 4 prong that you describe. I hadn't seen those at the time, but have used them on other projects since. I still have a 4 prong that tucks up behind the bumper. I haven't noticed any chrome peeling, but the flange of the plug covers & holds around the edge of the hole.
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
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7,806 Posts
Normally I'd edit that ^ post to add this, but since the forum downgrade I haven't been able to get into any old posts because of the 7 day 10 edit limit that apparently I keep burning up correcting new posts.

I don't know if a 95 still uses that rubber moulding, but it looked good on the 90.
 

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Premium 4 Lyfe - Way Back Staff
'95 XLT: 5.8, MAF, E4OD, 4.56's, 6" lift on 33's
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35,881 Posts
Discussion Starter #8
No rubber molding down the center of mine but enough there for "footing" that it won't look terribly out of place, I think.


The 7/4 plug will need a little trim on the top and bottom to fit snug, due to the "bumps" on the top and bottom but not enough to be a concern. (y) Glad to hear it wasn't a bumper destroyer.
 

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I have chrome peel on my bumper from where it got bent by a trailer jack years ago, but it never spread.
I test trailer lights with a battery, never assume the truck is ok first. Same applies to a 7 way just haven't gotten around to making that video yet.
95s had factory brake controller wiring, there's a square plug under the dash to connect the brake controller.
 

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Forgot to mention. I considered relocating mine to the bumper because I kept hitting it an bending the mount on things. I opted not to as putting it in place of the plate light would leave it very vulnerable to getting smashed by the trailer tongue (my plate is pretty banged up, the one from my bumper hitch days was nearly unreadable) and on the back face would have made it vulnerable to getting smashed by the trailer jack, or anything I bump into. I ended up building a ultra strong mount for it and put it right next to the hitch. Its strong enough that you can jack the truck up with it (which I actually did) and survived a trip to hard rock, minus some paint from the bottom.
 

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Premium 4 Lyfe - Way Back Staff
'95 XLT: 5.8, MAF, E4OD, 4.56's, 6" lift on 33's
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Discussion Starter #11
That's an interesting point about the trailer tongue banging the hell out of it... especially since anything new is plastic. I had planned to move it over to the left of the bumper plate well, rather than in place of the light, for ALL the same reasons but now that I have a welder, I may have to consider the custom mount box option. I prefer clearance but the hitch is there anyway and I've been hung up on it before but that may have been on the old '90 that had no lift.

Got any pics to share of that custom box setup? May copy or take lessons learned when the time comes, again. (y)
 

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160054
160055

This was after hard rock. It started with a expedition plug mount, which I only used one piece from. Then added material to completely enclose the back side of the plug.
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
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7,806 Posts
Here are some shots of my 90's trailer plug. I like it here a lot. It never gets hit offroad, it's far from getting hit by the coupling, & it's positioned well for the trailer plug to reach. Also, a little higher like this gives more ground clearance for the slack in the wire.

As you can see all chrome around the hole is hidden & held by the plug itself, so I can't see if there is any peeling. I still need to paint the screws black so it will disappear better.



 

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Premium 4 Lyfe - Way Back Staff
'95 XLT: 5.8, MAF, E4OD, 4.56's, 6" lift on 33's
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Discussion Starter #15
That's just a hair further over than where I was checking but I don't have the rubber trim. Figured I'd have my plug edge sitting just about where your rubber trim stops. I was thinking I'd grind off a little of the upper and lower mounting face, so it will fit smooth and flat. I can line the plastic edge with some of my E6000, just to seal it tight and hopefully keep the chrome from peeling away around the plug-hole edge.
Sounds like it's a perfect fit with clearance issues, protected and still a little off-the-side, so it's not in danger of being backed into and cracked or broke... as I had hoped.

I've been a little paranoid about chrome peel since my front bumper started to loose some of it's chrome in strips. Eventually, I'd like to use my welder and build some bumpers but metal is not cheap... and I am. :sneaky:
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
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7,806 Posts
Your placement & back-grinding sounds like it should work well.. I don't know about using the E6000 between the plastic & chrome because it seems like all trailer plugs eventually need work/replacement, & I wouldn't want it to pull chrome if removed. Maybe some dumb-dumb instead if it needs sealing. :shrug
 

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Premium 4 Lyfe - Way Back Staff
'95 XLT: 5.8, MAF, E4OD, 4.56's, 6" lift on 33's
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Discussion Starter #17
That's a potential issue. Maybe I should use something with less bite. Guess we'll see how well it fits up when I get around to it. ;)
 

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I can say I've looked at hopkins and ford trailer plugs and the Ford was way stronger. There was never any way it wasn't going to get hung up, that's why I beefed it up so much, so that it wouldn't matter if it did. I considered mounting it facing straight down between the hitch and bumper so it would never hit anything, but with how much I tow it would be a nightmare to get to.
 

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Premium 4 Lyfe - Way Back Staff
'95 XLT: 5.8, MAF, E4OD, 4.56's, 6" lift on 33's
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Discussion Starter #19
Yea... I noticed you had the Ford plug and even though I purchased the plastic Hopkins unit for the convenient 7-4 connection, I didn't toss the oem plug in the trash. Figured I'd keep it around and maybe refurb and re-use it or offer it up to someone like yourself for the same. I'm not a huge fan of plastic crap stuff... but that's why I wanted to discuss safer ways to mount and protect it.
 
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