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I'm trying to set up a boat trailer w/ 4 wires for my (supposedly) factory pre-converted connectors under the bumper. There two connectors; a 4 wire round and 2 wire round connector. The 4 wire has yellow and green, and I assumed they were for signals. Matching them up to the 4 wire trailer wiring, I do get proper turn signals at the trailer. When I try to connect brown to brown, which I believe is for running lights, I get no running lights and no longer do the turn signals work on the trailer. I notice that when disconnecting the brown to brown connection, I can hear a relay opening at the rear of the vehicle.
In any case, I am frustrated and lost on this one. Does anyone have any clues as to how I might make this work?
TIA,
Chris
[updated:LAST EDITED ON 17Jun2021]>I'm trying to set up a boat trailer w/ 4 wires for my
>(supposedly) factory pre-converted connectors under the bumper.
I feel your pain: I installed a Valley 2" receiver hitch (Class III, from an '86 in a junkyard) on my '89 standard-length yesterday, and spent many hours today on just this issue: factory trailer wiring.
I was careful to write down the wiring setup on the '86 prior to removing it's aftermarket can-o-worms (complete with diode isolator module that lacks any docs, but I'm used to that). It was (typical) patched in to the std wiring, and bypassed the trailer wiring module and harness altogether, not a very good job, either
{I really wanted that 2" receiver hitch -- all the others I've seen are the smaller size (1"? 1.5"?). Granted, the Aero likely isn't rated for 5,000 Class III pulling, but I like the extra margin. I had to remove the under-mounted spare and carrier, but it clears the exhaust very well. Uses the two stock under-bumper mounting holes for two pickup points, and four frame-rail mounting points, it's quite sturdy. The '86 in the 'yard had the frame points cut with a torch, and nutplates slipped up into the frame channels; I opted to cut 2" x 4" holes in the floor above and drop in custom 1/4"x2"x6"l flatbar nut plates that I made, with Grade 8 nuts tacked to it. This baby ain't goin' nowhere!}
$15 for the hitch assy at a U-Pull-It type 'yard, $20 of plated G8 hardware (lots and lots of new hard flat washers, split lockwashers, bolts and nuts), $10 to have someone do the tack job on the nutplates (my welder was stolen along with most of my tools three years ago), the usual costs associated with multiple drill bit acquisition, metal blades for the sabre saw to cut the floor, Dremel bits to tailor various holes, and the obligatory 4" cutoff wheels for the hand grinder
I took lots of pics, and someday when my website is online again, I'll post them.}
> There two connectors; a 4 wire round and 2 wire round connector.
I've got the AllData CD, with trailer wiring diagram, and it's much less than obvious: the small two-wire connector is basically for the backup light! But! That's just the Bk/Pk wire. The two-wire connector's BK wire is actually a ground loopback to the Trailer Tow Relay Module (TTRM).
> The 4 wire has yellow and green, and I assumed they were for signals.
Since I've got a heavily-marked-up printout of the circuit to my left, and this project is fresh in my mind:
Four-wire round connector:
Left turn: LG/O (Light Green w/Orange stripe)
Right turn: O/LB (Orange w/light blue stripe)
Running: BR (Brown)
Ground to chassis: Bk (Black)*
I had to use an acetone-soaked rag to clean the undercoating and road grime from the wires to match the diagram.
>Matching them up to the 4 wire trailer wiring, I do get proper turn signals at the trailer.
For a while! You were just lucky. Put any kind of a load to ground on the TTRM ground feed, and it'll try to energize the relays. Sometimes.
>When I try to connect brown to brown, which I
>believe is for running lights, I get no running lights and
>no longer do the turn signals work on the trailer. I notice
>that when disconnecting the brown to brown connection, I can
>hear a relay opening at the rear of the vehicle.
>In any case, I am frustrated and lost on this one. Does
>anyone have any clues as to how I might make this work?
I have not actually made connections to final form yet, but what I assume is supposed to happen is that you use the real Ford adapter harness to connect to BOTH the two and four pin round connectors on that center harness. Then the four-wire Bk ground is connected to the the two-wire harness's Bk wire, thereby providing the ground for the TCM, enabling the three relays next to it:
a) Running lights relay (four wires, two Y, two Br)
b) Left relay
c) Right relay
This TTRM is behind the jack. [2021: Here's a poor picture of it removed (the twisted-together wires are where the next owner after me blew the fuse, cut out the fuseholder, and this was his "fix". I bought the van back a couple of years later, and that's where this pic is from]:
It's a bit of a twist to get it out, but you don't need to, probably ever. [Edit: except! Ford buries a fuse inside it. If you short your trailer wiring, guess what you have to do when the fuse blows! It's not fun to get to ]
I had it all apart today -- the wiring diagram treats these three relays plus an electronic module as a "black box" monolithic unit, which is useless if you need to actually know how it is supposed to work! Don't bother taking it out.
I assume that the reason for this TTRM is to take the load of the additional trailer lights off the standard brake/turn/run system, and the three relays and the associated (much heavier!) wiring that the TTRM has for outputs are very nicely done. It also should keep the flash rate consistent, because there is no additional load on the thermal flasher up front. But, the relays are rather noisy (every brake, every turn, and turning on/off the park lights triggers a relay click) so I assume that Ford went to this loopback enable system to shut the relays up when they're not needed.
I'm not going to chase buying the Ford harness adapter, I'm going to hardwire the two-pin round connector's Bk ground wire to the chassis, and live with the relays clicking all the time. This enables the TTRM electronic module, which then energizes the three relays plus the L/R combiner for the single-output brake light.
This is what I came up with after about 2.5 hours today, trying to do about half of what you've gotten to. I haven't acquired the trailer to match this setup yet, so I'm not really in a rush to terminate the harness at the new bumper connector yet, but if you, like me, do not want to buy the Ford harness adapter (I assume from the diagram that that's what I'd need) then just ground the two-wire round connector's big black wire, and listen to the music
Now, for the question that I came here to ask:
a) Can one of you folks that tow with the stock setup confirm that the adapter harness (from the stock harness connector at the center behind the bumper, to the trailer) exists,
b) Where did you get yours? Is this a Schucks/Kragen/Autozone/NAPA sort of thing, or dealer-only? If it's reasonably priced, I'd go buy the harness adapter (as the mating male round connectors aren't something I can easily lay my hands upon from my normal electronics suppliers -- it appears to be a connector only used in automotive applications, AFAICT, else I'd build an OEM-style harness myself and be done with it).
c) Bonus/bogus question: the the Hell is the two-wire flat connector under the left tailight area for? Two little pink wires? There's an identical connector up above the jack area inside. I have no idea.
I don't know exactly what the cutoff year is . . .
To recap:
Aerostars could be ordered with a factory towing wiring setup. If yours has factory towing wiring, there will be two roundish connectors underneath the back, just to the right of center, about 3" behind the bumper, and they are plugged into dummy terminators, to keep them clean and up out of the way.
You will also have a Trailer Tow Relay Module (TTRM), located on shorty Aeros behind the left wheelwheel, behind the jack. It's a roughly triangular aluminum box. If you just have a black plastic insulation "pillow", you don't have the TTRM. I do not know where the TTRM is located on extended-length Aeros.
The idea is to be able to wire your trailer (using a Ford adapter harness, purchased separately, on the trailer) so that when you plug in this Ford adapter into the two towing plugs underneath, the TTRM is enabled, and the RightTurn/LeftTurn/Brake/Running/Backup lamps on the trailer are powered by relays in the TTRM, and not via the normal circuits for the van.
It's worth repeating: even if you have the optional factory-installed towing wiring setup and TTRM, it's the trailer adapter harness that enables the system. The towing connectors are more or less completely DEAD unless you plug in the Ford trailer adapter harness to the towing connectors.
I visited my Ford dealer yesterday and was told that Ford no longer supplies the trailer adapter harness for Aeros prior to '93 (which is why the subject of this post is worded the way it is).
Today, armed with wire cutters, I visited three junkyards and got luky: I found ONE Aero (a '90) with the Ford trailer adapter harness still installed (that owner used the trailer adapter harness to build a further adapter to his trailer wiring, probably so that he could use his trailer on more than one vehicle. Smart.), so I have a sample. Not too surprisingly, it's wiring matches the schmatic on the AllData CD.
On the theory that I, or one of you reading this, might want to built this trailer adapter harness yourself (rather than taking the easy way out, chopping off the undercar connectors and using the wiring pinout I posted earlier to build your trailer adapter that way), I walked up and down the rows, looking for a source for the two connectors, and I found them. The list that follows is for the connectors you need to plug into the optional factory-installed towing harness under the Aero.
Two-pin connector:
1) Good: The charge air sensor (about halfway back on the left side of the intake manifold (right side as you view it) on the top) from pretty much any 3.0l in any Aero is the right connector. I looked at about a dozen, and they all look correct. Note that the easier-to-get -at coolant sensor on the 3.0l (right up front, above the water pump) has the mating "square edge" on the wrong side, so forget using that one. The wiring is of a rather light gauge, but that's OK, because if you recall, the wiring in that connector does real light work:
Black: ground it to enable the TTRM
Black w/pink: backup lights
Cut it off the donor harness.
2) Better: '87-88 Aero: There is a good connector under the air filter. It is not on two '88s I looked at, nor on one '86. I have no idea what it feeds. Follow the A/C harness from the compressor back up to the body, past the first connector, and where it meets the fat harness just in back of the air filter housing (and below, to the left of the fan) is a short (2") harness with the correct connector. It has heavier wire than the above. Cut it off the body harness.
3) Best: Any '87-91 Taurus w/AT. I don't know what it's for -- possibly the radiator fans -- but on every Taurus within those years that I looked at, they all have a white ceramic resistor block bolted atop the automatic transmission, and the body harness connector to which it connects is perfect. Heavier gauge wire than the one above.
Four-pin connector:
1) Good: '86 Ranger w/2.3l 4 cylinder, FI, and manual trans. The oxygen sensor harness on the FI rigs is for the heated EGO, which seems to have three wires. The harness has four wires, though; where the fourth wire goes I don't know, but if you follow the oxy sensor harness from the sensor up to the body, where that lower harness connects on the right fenderwell is the perfect connector. Cut it off the body harness.
2) Better: '84-86 T-Bird or Cougar. On the left fenderwell, to the rear of the coolant recovery tank (which is bolted above a rack of vacuum solenoids), adjacent to the A/C compressor, is a bunch of harness-to-harness connectors, one of which is the correct one. Watch out for the gender, because I can't describe to you which one to take, because they're both body harnesses -- of the few I harvested, the correct one was the "front half". You want the "larger" half. On every one I pulled, the connector has all four wires wired/pinned, but the two black (brown?) wires were stubs and only 3" long. Good for us!
3) Better (maybe): '87 T-Bird. This may be a one year only thing, because '89 is different, and I didn't see any '88s to compare. Find the wiper motor (driver's end of cowl, top of firewall, in engine compartment) and there's our connector, along with two or three other ones. Some of the wires are a bit heavier than the ones above. Watch for the gender. You want the "larger" half.
Armed with one two-wire and one four-wire connector (and the pinout below) you can make your own Ford trailer adapter harness. Use the wire color on the undercar harness and the list below for function:
Code:
Four-wire round connector:
Left turn: LG/O (Light Green w/Orange stripe)
Right turn: O/LB (Orange w/light blue stripe)
Running: BR (Brown)
Ground to van chassis: Bk (Black)
Connect the two-wire's black to the four-wire's black using the pigtails on the connectors you harvested from the junkyard (those colors will vary, of course). That connection will enable the TTRM, and you also use it for the ground on the trailer.
The backup light is optional, of course, and you don't have to connect it to anything. Most especially, don't connect it to the TTRM enable (which is what you would guess, if you were guessing).
I harvested enough connectors today to build a couple more harnesses, should someone be interested in buying one pre-soldered and ready to connect to your trailer. Optionally, give me a pinout of your trailer's existing connector, and I can solder on a mating connector on this end, so it would be "plug and play" for real.
But the data above should allow "anybody" to build it themselves. As usual, it's not too difficult -- once you know how
Kinda on the wrong board here, but figured I might be able to help a bit. I'm a U-Haul system member (during the summer), and have worked on several Aero's with wiring difficulties. By far the best setup I've seen so far is the quick-connect kit we sell at our Centers, and Hitch Centers. I dont have the part number right here by me, but its plug and play, literally.
Sorry to butt in...hopefully this'll help somebody!
I see now that the board's reformatting of my links in the intervening time since 2002 has f**ked up the display (three posts upthread), so here's the wiring diagram again.
01-24-2002, 09:10 AM
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'92 Extended E.B. Aero Trailer wiring
