Uncertainty about tow harness wiring options

I've learned a lot about towing over the last couple of days, and am still uncertain about some things with the wiring.

I drive a 1998 Explorer 4D 4WD 4.0L XLT. I am making a one-time haul 1000 miles there and back. The trailer is small and has a 7-round connection. I am not going to connect the brakes nor the power wire to the trailer battery and am only interested in the lights. I am doing this on as much of a shoestring as possible. I do not (believe) I have the towing package. I am still trying to figure out what tranny I have. I have amber rear turn signals.

I have read a lot and have visited the Ford dealership and NAPA several times. I have a doctorate (not in wiring) so I'm not exactly dense. I get a little frustrated with answers (such as from the dealership) that start with: "Generally, maybe, probably it should work...[without toasting your computer or other electronics]" I am under the impression that wiring is either right, or not...sort of an all or none thing...

The Ford man looked under the truck where I showed him the wiring jack. He confirmed that is IS a wiring jack and said that it "looks like" it has the brown and yellow and other wiring. (I'll look myself tomorrow; either it IS wired, or it is not)

At Ford Parts, I was delighted to find that Ford has a part (13A576) that plugs directly into this jack tucked up behind the bumper under the car. This harness will magically turn the jack underneath the truck into a 4-flat. The Ford man said I should be good to go. I can adapt the 4-flat to a 7-round (lights only) with a part from Napa.

Also at Napa, I located something that looks just exactly like the $51 Ford part for less than $16. (755-1547) Problem is that it's described as being for my truck WITH the tow package which I believe I do not have.

There is another Napa part (755-1566) for $82 that requires a bit more installation the most difficult of which would be running a wire to the positive pole of the battery. I can probably handle that.

See, the $82 Napa [Hopkins] part has a little power converter and also mentions a fuse assembly. The $16 part is pretty much just a harness with the right connections that appear to match the Ford part.

So, my dilemma is this: Which to get??? $82 or $16? (+4-flat to 7-round)

I asked the Ford man about overheating things and needing a fuse. He said there's already a fuse in the truck's fuse box. I asked which fuse? --to which he said "it should be labeled 'acc', as in accessory" Later, looking in my manual I found two fuses involved with trailer lights, (#30 and another)...there are none labeled "acc". Are those two involved fuses enough?

Now, might these Ford guys be kind of ~forgetting~ to tell me that I'll roast my expensive truck computer if I don't have some kind of converter? Am I just too unforgiving about the "maybe"s and "should be"s ??? Am I pressing too hard for a definite answer?

I just want to take my son's stuff to him for school...and now I'm in a quandary...should I just buy the $16 Napa part and see how it goes? Am I taking too big a risk?

What to do?

I wish SOMEone could tell me what is it about the factory Tow Package that makes it OK and risk-free to use the cheaper part.

Sorry for the long post; hopefully there's enough information for a relevant and useful solution.

Thanks you in advance,

drcarl


PS - If someone happens to know where I can find my tranny specs, that'd be cool, too...

From what may be relevant from the sticker inside the door (I have no clue what all these might indicate) :
RC: 56
WB: 112
BRK: 4
INT TR: ZE
TP/PS: P/
R: K
AXLE: 46
TR: D
SPR: BF

 

[dogfriend]

Hi DrCarl

AFAIK (as far as I know) the 2nd Gen Explorers are equipped with a relay to protect the wiring (i.e. the $82 module is not needed). Regardless of whether you have the tow package or not, there should be a connector tucked behind the rear bumper just to the right of center that is for the trailer light connection (stop, turn, taillights). The Ford harness (which I bought) just converts from the Ford proprietary round connector to a generic "flat 4" connector that most trailers use for lighting. There is nothing special about the harness other than the matching connector that plugs into the factory wiring harness.

So, I think you will be good to go with the harness (Ford or otherwise) and an adapter from "flat 4" to a 7 way to match the trailer.

P.S. You have a 5R55E transmission. You should be ok towing as long as the weight is low (<2500 lbs). If you aren't using trailer brakes, you should be less than 1500 lbs anyway. If you tow a lot, you should add an external trans cooler.

 

[gijoecam]

Get the $16 part. So long as it's for your year and plugs into the factory harness, it'll be just fine. The isolation circuits for the trailer wiring should already be in place from the factory. All second gens come wired that way. (The connector for the 95-96 and some of the early 97s is different than the 98-01, but it's there none the less) With or without the towing package, the wiring is there. If you had ordered the truck with the towing package, they would have installed the harness as a part of the prep at the dealership. The tow package also gave you a larger battery, ensures you got the larger alternator, and the auxiliary transmission cooler (you automatically have on built into the radiator because it's an automatic).

Now, as for towing capacity of the vehicle, we know you have a 4.0 liter motor, but you haven't told us if it's an SOHC or an OHV motor (it'll be molded into the plastic cover under the hood if you're unsure). We know you'll have the 5-speed automatic trans, and from teh door sticker under the AXLE code, #46 translates into a 3.73 non-limited slip differential. So, from that info, we can refer to page 130 of your owner's manual and see that the towing capacity for your vehicle will be 5160 lbs with the OHV motor or 5640 with the SOHC motor. In either case, unless you're hauling a car in that trailer, you should be within the truck's limits. However.....

A frame-mounted weight distributing hitch is required for any trailer weighing more than 2000 lbs (per page 131 of your owner's manual). Ironically on page 132, it states that the bumper hitch is rated for 350 lbs tongue weight, 3500 lbs gross trailer weight, and a frame mounted weight distributing hitch must be used for trailers over 3500 lbs. (In direct contradiction of the previous page) Personally, for anything over 1500 lbs, or for a long haul, a frame-mounted hitch gives you the flexibility to adjust the ball height up or down to level the trailer by using the various ball mounts that are available. A level trailer will tow much better than one riding tongue-high or tongue-low.

Speaking of the towing experience, having towed without them, an enclosed trailer is going to be about 1000 lbs to start with. Load it up, and you're easily looking at 2000+ lbs. It'll stop, but it's not going to like it. I prefer brakes on anything over 2000 lbs. Having a brake controller installed by a camper dealer or hitch shop (NOT U-HAUL!!!) would be worth it IMHO, especially if there are any mountains or city traffic involved. I wouldn't personally tow much more without them (but that's just my opinion... Other opinions will surface, I'm sure). Be sure you have no more than 15% tongue weight on the back of the Ex, and even then, don't pack the rear of the Ex with gear too. It's VERY easy to overload the rear axle with as little as 300 lbs of tongue weight. (It puts my Sport within 50 lbs of the gross axle weight rating)

Hope that helps... Good luck!

 

[Gatorblazer]

The easy plug in is well worth the extra money. I think I got mine from Autozone for $40, but that was 5 years ago. The frame mounted hitch is a must I think for anything over 1000lb. They are cheap and easy to install. Getting a pigtail and a frame hitch will make your Explorer a pretty good little tow rig provided you stay under around 3000lb. If you exceed that, you will need trailer brakes, but that is not a terrible expense either.

Dont know if your borrowing the trailer or planning on renting one, but just in case you didnt know, UHaul will not rent a trailer to you. If you search for UHaul on this site, you will see many threads regarding this.

 

[drcarl]

Nice!

Thanks Dog and Gi...awesome solid information.

I have the SOHC and will be going from Seattle to Santa Barbara pulling a friend's brand new Pace 8' enclosed trailer weighing 1300 lbs.

I know that, as-is, I'll be tongue-high...will go hitch it up today to see how far off level it'd be. I am trying to do this on the cheap and really hope to avoid yet another expense of the preferred frame-mounted hitch...(might visit some junkyards). Though this trailer has brakes, I fear the brake controller install is expensive...I'll call the man for a quote.

Bottom line is that I learned a LOT from the site and from your direct answers. Enough to know that the $16 harness should work, and that I am pushing it weight wise, to balance the load (I have no tongue scales), and to keep it really light. Besides the trailer itself (and we 3 humans), I'm only packing/hauling a twin bed, a dresser (kinda heavy), a night stand, a computer and small desk, and a closet of clothes. It's a typical kid's bedroom.

I'll get the $16 part today and try it. I wonder if there is a "test" to know it's OK, though I feel more assured that it is now. (I hope the test is not blown wiring!)

Thanks so much for the good info.

--drcarl

 

[gijoecam]

Hit up a junk yard and pick up a potentially questionable hitch from a salvage... For probably $40.

Or...

For less than $100, buy a new one and know you've got a solid one, use it, then sell it for $75 on Craigslist when you're done, but know you've got a solid hitch for the trip.

When loading the trailer, resist the urge to put all of his stuff in the front of the trailer. That'll put way more tongue weight on it than you think. You shouldn't be able to lift the tongue alone, but two of you might barely be able to (I'm guessing 10% of a 2000 lb trailer....). If you get too light on the tongue, you'll get an excessive amount of sway, and that's NOT much fun.

 

[drcarl]

Great!

Great info...thanks for the practical tips...especially about a couple of guys lifting the tongue...I was kind of figuring that mentally but am glad to know that some tongue weight helps in the sway department. Thanx!

drcarl

 

[Gatorblazer]

Academy and Autozone sell a plug tester for less than $5. It plugs into the 4way flat and has small lights on each wire. When the wire recieves signal (turn signal on either way, brake lights on, tail lights on) the light will show green.

 

[drcarl]

update

UPDATE: installed the $16 Napa part and the $39 4-flat to 7-round (RV) adapter and plugged her in. Running lights: OK. Left signal: OK. Right signal: OK. Brake lights – poof – nothing. All lights out. Discovered that on my Explorer, the left running light (when the headlights are on) is OK but the brake light (the second part of that lamp) was toast.

I’d LOVE to know if the setup I had caused this brake lamp to expire or not. The running lights half was OK. Who knows? Might have even been a coincidence. Sure as heck, though, no lights on the trailer lit up after I tried the brake lights.

Took all the parts back to Napa and ordered the $89-whatever harness with the thing-er-ma-bob computer unit (that I can’t right now remember the name of; protects the circuits or something). Have to use a 4-flat to 7 round (RV) adapter, too. Hope it works.

Look forward to your input.

Thanks,

Dr Carl

 

[gijoecam]

By 'poof', do you mean you blew a fuse, or do you mean that the lights just went out? If you blew a fuse, we have a problem. Otherwise, it sounds to me like a simple grounding issue. I suspect all the lights were grounding through the one that blew. Nothing on the truck made it do that, and the harness isn't likely the cause. The only thing that can go through it is a simple 12V signal. I suspect the issue is on the trailer, not your truck. 10 minutes with a multimeter or even a simple 12V test light can pin down the problem in no time.

 

[dogfriend]

Yes, I agree, I don't think it was the $16 harness that caused the problem. I have been using the Ford adapter harness (I think I paid ~ $25, but that was many years ago) and have used it with my camping trailer and several rental trailers without any issues.

 

[drcarl]

Ok...hmmm

By "poof" I mean that there were suddenly NO lights at all on the trailer. I could not find any fuses blown on the Explorer, though I only checked the fuses in the driver's side dash and none of the Superfuses (?) under the hood.

I don't have a multimeter. Don't even have the simple 12V tester (unless it's that screwdriver-like thingie with a wire? and a small orangish bulb/tube). I suppose I could buy a tester...but then what? I rock with a camera, but don't know how to use the tester (where to place it) and I also don't know how to interpret results.

Pretty soon, I'm headed to Napa to get the more elaborate harness, and the 4-flat to 7-round (RV) adapter.

Sometimes I think I should have just come up with the money to pay someone to do it...yet, I certainly would nopt have learned what I have.

--drcarl

 

[dogfriend]

The fuse for the trailer lights is in the Power Distribution Box under the hood. It is a 20 Amp fuse. If the fuse is blown, I would suspect a short somewhere in the trailer wiring.

 

[Verno]

By "poof" I mean that there were suddenly NO lights at all on the trailer. I could not find any fuses blown on the Explorer, though I only checked the fuses in the driver's side dash and none of the Superfuses (?) under the hood.

I don't have a multimeter. Don't even have the simple 12V tester (unless it's that screwdriver-like thingie with a wire? and a small orangish bulb/tube). I suppose I could buy a tester...but then what? I rock with a camera, but don't know how to use the tester (where to place it) and I also don't know how to interpret results.

Pretty soon, I'm headed to Napa to get the more elaborate harness, and the 4-flat to 7-round (RV) adapter.

Sometimes I think I should have just come up with the money to pay someone to do it...yet, I certainly would nopt have learned what I have.

--drcarl

Dr Carl, it sounds like your ball and hitch are not making good ground. If you have a spare piece of wire, try connecting it from the trailers ground connection of harness (white wire) and other end to the frame. If lights work yor problem is insufficient ground. With the test light (looks like a pencil with wire coming out end) connect the clip of wire to a good ground (metal) on your truck. Try each of the lights (LT,RT,TAIL) individually and stick the point of the test light into your connector (withou trailer connected). That will tell you if truck is wired correctly FIRST, then try it after connecting the trailer harness (be sure to do second check behind-after harness connector on trailer end.

 

[gijoecam]

Dogfriend, thanks for that schematic!!

If you weren't 2500 miles away, I'd offer to lend a hand myself... If you didn't blow any fuses, it's not a problem with the harness on the vehicle. The one you had was fine.

It's displaying the classic symptoms of a bad ground. Turn parking lights on alone, and they work. Hit the brakes alone and they work. Hit the turn signals and they work. Hit the brakes or the turn signals with the parking lights on, and nothing. Grounds are a funny thing on trailers... They are finicky, and can find alternate paths through other light bulbs in other fixtures. If you happen to try to force them all to ground through one bulb's filament, it'll act like a fuse. The root cause is a grounding issue on the trailer, not a power issue in the truck.

And don't let them sell you the isolation module for the Ex. You already have one incorporated into the truck's wiring.

I would also agree that a simple alligator clip on a jumper wire (Autozone, $5) with the wire connecting the truck to the trailer could be verify the problem. It does sound like a bad ground back to the truck. 5 miles down the road, they may start working again, as the ball rubs the rust off the coupler and re-establishes contact.

-Joe

 

[drcarl]

Fascinating ....here's a news flash...shows how I can know a lot in one area and perhaps be a moron in others...I'll form this thought as a question:

Q: Does it matter that the hitch was not on the ball?

The trailer was not touching the Explorer...I just plugged-in the wiring array for a test. Would it be different with the trailer actually attached to the truck???

(I have not fully read the previous two posts and will in a bit)

 

[dogfriend]

q: Does it matter that the hitch was not on the ball?

yes!

 

[gijoecam]

Certainly could... In the 4-pin connector, you have a parking light circuit, a left turn, a right turn, and a ground. If the ground wire on the trailer is not connected securely, it could allow a little bit of current through for the parking lights, but add in the brakes/turns, and it overwhelmed the crappy connection.

On most small trailers, they run the wire into the frame channel, and make the ground connection with nothing more than a zip-screw through the frame rail. I'd see if you can chase down the end of that wire and see where it's connected. I *suspect* you'll find that if it's not loose, it's severely corroded. Dropping the ball on the hitch can *sometimes* provide an alternate path to ground, but it's not always a reliable path. I wouldn't count on it.

The afore-mentioned jumper wire with a pair of alligator clips would be the quickest, simplest way to try it out.

 

[drcarl]

wow

You guys are AWESOME!!! What a fast reply! I'm breaking out the trailer manual and reading these posts more slowly after I make some coffee. It takes me quite a while to make a cup since I hand-grind my beans with an antique burr mill for grind uniformity. I get cups we rate consistently as "9.7" or "9.8" on a 1-10 scale with 10 being a blowmind cup. What I'm saying is that I'll not post for a bit.

And, dogfriend...I'll interpret that as a "Yes" -lol- Sheesh.....

drcarl

PS's

1) The trailer manual refers to a ground wire and says that it must be connected to the tow vehicle's frame...I just plugged the harnesses together and did not even look for a ground wire.

2) Manual also says that if I have amber turn signals, I must "see your hitch and wiring specialist for installation of a relay or "splitter" to operate your trailer turn signals and brake lights". As you probably know, that's the more expensive harness with the hot wire to the battery...the trailer man seemed to think that the relay would not be necessary since so many of the incandescent lamps on this new SMALL (<--not a lot of lights) trailer have been replaces with LED's.....which to get? (I'm getting both..now, which to install?)....am getting a wire with a couple of alligator clips, too...in case there is no available ground wire available from the trailer.

BTW - after the lights stopped working with my truck as the tow vehicle, I hooked up the owner of the trailer's car which is properly and professiuonally wired (ground and all, I bet) and even without the hitch on the ball, all was good on the trailer.

--Off to Napa (will try the $16 connector again first), then 20 miles to the trailer, then hopefully home with the trailer...have not been able to bring it here without lights--

Thanks to ALL of you...

drcarl

 

[gijoecam]

You will NOT, under ANY circumstances need the relay as mentioned in your second point. That is already built into your truck's electrical system. Adding one would be redundant. The signals sent to the trailer connector have already been isolated from the truck's wiring.

Just thinking out loud.... Double check the wiring arrangement on the harness... If my memory serves, there was a change in that connector's pin arrangement at some point during the second generation. There was something weird about the four active pins in there.... I don't recall what it was, and it would take some deep searching. I don't have all my schematics in front of me, but the Ford pigtail should work just fine. (It's the one I installed several years ago)

-Joe