40amp tow fuse blows/loss of brake/turn signals

02-20-2005, 12:45 PM

Help!! We purchased our 1st Trailmanor - 1998 2720SL last Jan. On our second trip our break lights and turn signals on the trailer only quit after we plugged in and drove off and the 40 amp fuse in our P/U truck blew. I figure there is a short somewhere. We found the fuse and replaced it and it happened the next time we plugged in and drove off. Since the closest TM dealer is 3 hrs away, and the locals are so expensive, I'm hoping someone here may be able to give me and my husband some trouble shooting hints. My husband had some electrical training years ago and has a meter. Would greatly appreciate any tips!!

ripp1202 · 02-20-2005, 05:17 PM

I would tell you to break the circuits down and start checking with a ohm meter to ground. I hope you find the issue then you wil know what to replace.It will take time to find but I hope you get lucky

**Bill** · 02-20-2005, 07:05 PM

Quote:

Originally Posted by ripp1202

I would tell you to break the circuits down and start checking with a ohm meter to ground. I hope you find the issue then you will know what to replace.It will take time to find but I hope you get lucky

You say that you lost the turn signals and brake lights. I take this to mean that you lost them on both sides - and also that the running lights, backup lights, etc, are still OK. Based on that assumption, let's do this.

Ripp is probably right - you may need to break the circuits down. I might suggest the following sequence of testing.

BEFORE YOU PROCEED, UNPLUG THE TM FROM THE TOW VEHICLE. UNPLUG SHORE POWER TO THE TM. AND DISCONNECT THE TM BATTERY. You want no power anywhere in the TM before you start.

The tow vehicle connector has 7 contacts, so of course the cable that leads from the connector back to the TM has 7 wires. They are:
o Brown - right turn/brake light
o Red - left turn/brake light
o Green - running lights
o Yellow - backup lights
o Blue - electric brakes
o Black - battery charge line
o White - ground
If you care to, you can see the connector diagram HERE. From the sound of it, your problem is with one of the first two circuits - brown or red - so we'll concentrate there.

First, remove the red lenses from the left and right stop/turn lights on the back of the TM. Remove the bulbs from their sockets, and peer around inside the fixtures. Do you see any sign of loose wires? Loose sockets? Heat/burn/scorch? Massive corrosion? If so, you have found your problem. If not, leave the bulbs out of their sockets, and continue as below.

In my 2002 2720SL, and I think in your '98 model, the cable from the tow vehicle plug is routed to a small box under the kitchen sink. Go under the kitchen sink and find the end of the black tow vehicle cord. Find the brown and red wires, expose their connections (just remove the wire nuts, but don't unravel the wires), and measure the resistance from each one to ground. Since the bulbs are still out of their sockets, the measured resistance should be very high. If one wire has a very low resistance to ground, that is the culprit. Recap the other connection.

The next question is whether the problem lies upstream (toward the tow vehicle) or downstream (toward the light sockets) from the junction. Unravel the connection to give you two ends, and measure the resistance from each of the two ends to ground. If you find a low resistance on the end that goes toward the tow vehicle, then your problem is up there, somewhere in the black cord or connector. In that case, you will need to replace the entire cord and connector. (Not too expensive, and easy to do - but not likely.) If you find a low resistance on the end of the wire going toward the light sockets, then your problem is down there. You need to follow the wire from under the sink to the light socket, looking for a pinch/corrosion/broken insulation that could result in a short.

Let us know what you find, and if more procedure is needed, we will do it.

BTW, what is your tow vehicle? And was the 7-pin connector on the bumper installed by the factory, or as an aftermarket item?

Bill

02-20-2005, 08:12 PM

Bill,
The tow vehicle is a 97 Ford F150 Lariat with factory installed tow package and aftermarket brake controller( we pulled a travel trailer with no light problems). Thanks for the info- I will check it out ASAP.

Newlegs

Harry Womack · 06-20-2005, 06:12 PM

I was underneath my 2005 3124KB trailer and found that the blue brake wire was trapped between the frame and metal floor and smashed flat. It was almost shorted out. Also in the refreg. vent area I found a wire trapped under the wall where it meets the floor. To remove the wire from under the wall it pulled all the insulation off of the wire.
Harry

06-26-2005, 03:21 PM

Just got back from our first voyage with our '99 2720. On the return trip we stopped for maybe 10-15 minutes to talk with friends. Since it is a hot day (mid 90's), I left the engine idling with A/C on. Anyway, when we went to leave, I found that my Prodigy had no power (dead display). Opened hood, found nothing wrong, tapped on the 2 fuses & got no change. Anyway, within 5 minutes it was working again and was fine the rest of the way home.

I'm thinking something got heat-soaked under the hood? Definitely want to figure this one out. Last thing I need is a randomly failing brake controller!

Now, the similar part: when we got home I checked the trailer brake & turn signal lights - none one are working, but all of the running lights (including the rears) are fine. I have power to the turn/brake lights at the Bargeman connector on the truck side but nothing after that. Something in the trailer wiring has gone south during our trip. Oh joy.

I'll check the under the kitchen cabinet as Bill suggests & see if anything turns up. Maybe it has to do with where the wires go to the rear shell...

Steve

**Caver** · 06-26-2005, 03:39 PM

Intermittent electrical problems can be difficult to find. Be patient and try to figure out the wiring and isolate the problem. It's usually simple once you find the specific problem. There is a junction behind the refrigerator where the battery wire connects to everything else. Both positive and negative have large wire nuts to create the junction. Check this carefully since there could be a poor electrical connection.

Tapping on fuses shouldn't fix anything. Fuses are designed so that once they have blown they will stay that way. I would be suspect of any circuit breakers that may be part of the vehicle power to the rear connector. I have two of these. There is one for the trailer and the other to the Prodigy brake controller. These are thermal devices and if the current is exceeded they open for a while and then close again.

I hope you find the problem without too much work. Ray

**Bill** · 06-26-2005, 04:29 PM

Steverino -

I think Caver Ray got it exactly right. I can' speak to your 4Runner, but my Ford has self-resetting circuit breakers on all the wires that go to the Bargman connector, and then on to the trailer. Heat-soaking these breakers under the hood could encourage one to open - and then driving away, and cooling the engine compartment a bit, could bring it back.

You also say that you have power to the Bargman connector on the truck side, but nothing after that. Presumably you measured the truck side of the Bargman with the trailer half of the Bargman unplugged. But what you really need to know is what is happening at the Bargman while the trailer is plugged into it. Tricky to get your meter probes in there.

There was an earlier thread that discussed a very similar problem. See

http://www.trailmanorowners.com/foru...ead.php?t=2135

In this thread, I outlined a measurement method that may help you.

Bill

06-26-2005, 06:21 PM

Thanks for your thoughtful responses...

I did some further checking (& sweatin' - jeez what a sticky day!)... Anyway, I found some bullet connectors on wires under the trailer - coming from the fridge area and going up the rear shell arm. Tested and got current on the two that are for the brake & turn signal lights. So I guess the next step is to check for continuity from that point to the light socket. I am presuming I'll find a broken circuit. The odd thing is that BOTH lights are misbehaving and they would not be linked (since they operate independently). I can't yet figure out the connection.

I'll be reading the suggested links for further clues.

Thanks,

Steve

ripp1202 · 06-26-2005, 07:17 PM

Could be a bad or intermittent Bargman plug on the trailer had one on my 3023 2004 , Bought a 6 foot molded Bargman and a bell box and spliced it in ,mounted the box to the trailer . Now I have two places to test at under the sink and at the bell box makes trouble shooting easier!

The Rip