Dead Breakaway Battery?  Maybe, Maybe Not

Over the last eight years we’ve had a lot of calls about breakaway batteries on Ironhorse Motorcycle Trailers.  Many of them start with “the wires on my breakaway battery are too short”, to which my inevitable reaction was “what are you doing taking the lid off the battery box anyway?”, as we fully expect them to last many years.  After all, the battery is supposed to recharge as soon as you hitch your Ironhorse to your tow vehicle.  Or so we thought!

Recently we had someone bring his Ironhorse back for a new battery after about three years.  He distinctly remembered that that when the trailer was first hitched to his Nissan, the recharging light on the battery box did not glow.  He also remembered that we had traced the failure to recharge to the absence of current on one particular pin of his seven pin receptacle.   Subsequently he had taken the Nissan to his dealer and been assured that everything was okay, but the battery still didn’t recharge.

Somewhat frustrated by then, and ready for a new vehicle anyway, he traded his Nissan for a new Ford F150.  But the breakaway battery still wouldn’t recharge.  By then he was convinced that there must be something wrong with the trailer wiring because a) there’s no way two vehicles in a row would have defective wiring, and b) the new Ford came with an integrated towing package including a built in trailer brake controller—totally set up for towing, or was it?

So he brought his Ironhorse back to us to get a new battery and have us fix the wiring problem.  Sure enough, I put the new battery on, hitched it to his new truck and —– nothing.  No recharging indication.  I then spent two or three hours looking for a problem with the trailer wiring before finally pulling out a test meter and checking the current on the appropriate pin in the seven pin receptacle on the new truck.

Imagine our surprise when, once again, there was no current on the appropriate pin.  By now our customer was getting angry and we were getting desperate.  So I grabbed the owner’s manual, searched for the appropriate fuse location, found it, and then looked for the fuse in the fuse box, but there was nothing there.  Then inspiration struck—when all else fails let your fingers do the walking—in a Google search box!

After typing in “F150 trailer tow battery charge issues”, it took at least a half second for Google to display a meaningful result.  It seems there is a slot for a “trailer towing battery charge” fuse AND another slot for a “trailer towing battery charge relay”, and that the required fuse and relay are typically in a plastic envelope in the glove compartment.  So I went charging back out to the customer’s truck and looked for the envelope in the glove compartment only to come up empty, and the customer didn’t remember having seen it.

By now the customer truly thought I was nuts, and who could blame him, but I don’t give up easily.  So I went roaring over to the Ford dealership about 300 yards from our plant only to find that, since it was Saturday afternoon, there was no one in the Parts Department.   BUT there were salespeople there and, after I explained what I was looking for, one of them opened a new F150 for me and sure enough, right there in the glove box was the plastic envelope of parts I needed.
Unfortunately, the salesman said he couldn’t let me take it and referred me to the sales manager—who happened to be standing next to a customer’s truck with his head in an owner’s manual trying to resolve exactly the same problem.  We quickly worked out a trade—if he’d let me take the package and come back and pay for it on Monday, I’d tell him where to put the fuse and relay in the truck he was working on.

Roaring back across the street, I stuck both items in the indicated slots, plugged the trailer into the truck receptacle and grinned from ear to ear when the recharging light came on!  Our customer, gratified although somewhat chagrinned, went on his way and I breathed a sigh of relief.  But I was still pretty pissed—why on earth would Ford put the relay and fuse for the towing battery charge in the glove compartment in a truck supposedly equipped with an integrated towing package?  So back to Google I went.

Here’s what I found.  First, unlike the majority of Ironhorse Trailers, many trailers don’t have a battery to recharge any way.  Second, packaging, but not installing, the necessary relay and fuse is apparently common practice among manufacturers to avoid liability if an improperly wired trailer catches on fire. Third, some manufacturers install the necessary fuse but not the relay.  Fourth, the necessary components are not always in the glove compartment—sometimes they are in a compartment in the door, in other cases they are packaged with the spare, etc.

The Bottom Line

If the battery charging indicator on your Ironhorse doesn’t light up or stops lighting up, check your tow vehicle’s owners manual.  Find the fuse section and look for something like “trailer towing battery charge”.  Once you find it, don’t stop.  Keep looking—this time for a “trailer towing battery charge relay”.   Note the specific “address” for each.  Then locate your fuse box, pull the cover and check the “addresses” you found in the owners manual.  If either, or both, “addresses” are empty, or the fuse is blown, your charging indicator is not going to light up until you replace/install the correct component(s).