I have a wells cargo trailer - 20' and it has internal lights. I use the big six pin plug that controls the electric brakes, the trailer also has a 12v battery on it to power the brakes I think. They worked fine, then I left them on too long and they no longer work. I replaced the bulb with no success. I have inserted all teh different relays, and fuses to get charging power back to the receiver. Any ideas of what to check next because I can't seem to find where it might be blown?

 

What tow vehicle?

 

Wow, can't believe I left that out - my bad.

1999 Ford Expedition 5.4l

I have inserted all relays to charge the trailer batteries, etc... (you know that kit it comes with).

 

Did your tow vehicle come with the factory tow package?

Fuse 23 (10A) in the CJB (Central Juction Box) under the dash supplys the current to turn the TTBC (Trailer Tow Battery Charge) Relay on and off.

Fuse 101 (30A) in the BJB (Battery Junction Box) under the hood supplys the charging current that passes through the Trailer Tow Battery Charging Relay and charges the Aux battery.

Check to see if you have voltage to the fuse holder. Fuse 101 should be always hot while fuse 23 will only be hot with the key in the "run" position.

If you have power at the fuses, move on to see if you have power at the control side of the TTBC relay with the key in "run" and that the supply side of the relay is always hot.

 

Thx PDQ, you always seem to have the answers or at least good things to check. Thanks also for spelling out the acronyms, I always wonder what they mean otherwise.

I am parking the Expy in the shop tonight so I will check the items you mention, thanks again and I will let you know how it goes.

Since I have your attention

I was thinking of putting two/three 12v batteries on the tongue of the trailer - to use when I can't use a generator. We use this trailer to sleep in and tow our quads and motorcycle. Since it already has a battery (I assume for the electric brakes) do you forsee any issues when hooking up these other batteries - ideally they will be charged to/from locations (although I will setup a trickle charger to). Will this hurt my expy in any way? I love my Expy- it has been so good and solid considering how hard I drive it. Thanks again.

 

Pdqford,

OK, well I finally got to try this out. I have very conflicted results however. The 101 (30a) was not HOT unless I turned the key on - I used a volt meter and when I tested it with key off - zero, key on - 11+ volts. Then I never actually got a voltage reading from fuse 23. The 10a fuse is good however.

The saga continues. I pulled the cover off the small battery that exists on the tongue of the trailer - it was horribly corroded - I hooked up another battery by using just jumper cables while I cleaned up the battery.

I went into the trailer and checked the switch - it has 10v to it. then I checked the area where the bulb connects - it's those little flat connector bulbs - it has 10v. I plug bulb back in - nothing. I use little jumper wires to test the bulb directly to a 12v battery - very bright.

Is it possible that I am losing just enough voltage 12v versus 10v that it would not light up a bulb?

I will replace the battery.

I also started the car and tested voltage to the trailer battery - 13v.

All this means that my Expy is ok (correct)?

I think it is in the trailer now but having trouble making sense of this bulb and voltage thing....


I know it's difficult - but any advice is appreciated.

Jason

 

Have you checked for correct voltage directly at your trailer plug at the rear bumper of the Expedition? I assume you have the 7-pin connector, so I've posted the pinout diagram below. You should have the same voltage across the black and white pins as you do across the vehicle's battery, whether is running or it's off.

 

Hmmmm. It depends on where you had your test meter. If you were testing down stream of the TTBC relay (on the OG wire) it wouldn't have any voltage unless the key was in the "run" position. If you were up stream of the relay (black w/yellow strip wire) it should be hot at all times.

Alloro has the right idea: test at the 7-pin connector at the back of the vehicle. Put your meter on pin-5 (fed by the OG wire) and pin-2 (fed by the white wire). It should show 0 volts with the key in the "off" position and vehicle (battery) voltage with the key in the "run" position.

The reason there is no voltage with the key "off" is because if you used the lights in the trailer it would also pull down the vehicle battery and you then may not have enough battery in the tow vehicle when you go to start the engine.

Additionally, by only having voltage with the key in the "run" position, a discharged aux battery would not put an extra load on the tow vehicle battery when you turned the key to the "start" position.

You need to have the key in the "run" position to get voltage through the fuse 23 circuit. Thats what sends current through fuse 23, activating the TTBC relay. Activating the TTBC relay is what passes the vehilce (battery) voltage back to pin-5 of the 7-pin trailer tow connector.

So if you can get vehicle power at pin-5 or the trailer tow connector, I suspect your problem is with in the trailer.

In your first post you said, "They worked fine, then I left them on too long and they no longer work". What did you leave on too long? And what no longer works?

 

You wanna try that again bud?

 

Yes, I would. But now I'm confused. Last night when I saw your previous post, your picture of the 7-pin connector would not display. Today it does. Maybe the picture you took is using the wire colors for the trailer?

I dug up a wiring diagram for the Expy/Navi and I was referencing the wire colors for the tow vehicle's wiring harness. It shows the ground circuit to be pin-2 (which is a white wire on the vehicle harness) and battery power on pin-5 (which is an orange wire on the vehicle harness).

Now here is where I'm really confused. Your picture of the vehicle connector shows vehicle power on pin-4 at the 2 o'clock position and the ground circuit on pin-1 at 7 o'clock.

The Ford wiring diagram shows vehicle power on pin-5 at the 3 o'clock position with the ground circuit on pin-2 at the 9 o'clock position.

Can you help us out, here, bud?

 

I'd like to but since there are conflicting diagrams, I think it's going to be up to jwhopson to do some testing to see which pins do what.

 

Hi guys, thanks for all your help. I started diagnosing it tonight thinking that I had the energy and I don't. I also really need to print this off so I have it with me. Additionally I must have made a mistake in prior post - when I tried taking voltage at the actual light - I said it gave 10v, but it actually was 1.0 and that's probably just something silly but regardless it wasn't 10. I did however change out the battery to a new one.

One thing weird in my super quick effort tonight is when I take voltage on the new battery - it reads -12? I don't do this alot with voltage meters but I guess I expected to see 12 not negative 12. I do have it connected correctly . But it makes me think that maybe there is a short somewhere in the wire. Also, I meant to use the electric brakes as a parking brake this weekend - by removing the emergency breakaway pin that you can pull out - simulates a runaway trailer --- guess what - it did not activate the brakes. Maybe the diode that charges the battery is bad (random thought). But this e-brake thing not working weirds me out.

Anyway, I will print your idea's tomorrow and try them. I just wanted to say thank you for your time and effort.

Jason

 

Are the leads plugged into the meter backwards?

 

Alloro, how embarassing, yes I had them backwords - although the one I was using is a pen and doesn't plus / minus so it's not too stupid of a move but still stupid ....

Thank you


Now - I decide to replace the two relays under the hood - trailer tow bat chg relay and the other one. Without doing anything else I decided to check and wholla - they work. Then I was upset that you have to have the key in the on position for them to work - so I pondered and hope this is ok. I decided to wire the black wire which is the lights in question directly to the positive lead from the trailer battery - now they work without the car hooked up.

Then when the trailer charge relay opens - it will charge the battery (yahoo). I can't imagine these lights using much power.

On another note I found a short. The 7 pin plugs in, then in the end of it I plug a six pin into it. Either it's worn or something but something is not connected 100% which I think is causing these intermittent errors. I can find that.

One more question - There is a diode that Wells Cargo puts in on the hot lead going to the battery, it's a one way charge so the trailer battery will not feed back into the car system. Do you know if there will issues with it having been connected to the lights in addition to the diode, the hot wire from the truck and the positive lead from the battery?



Thanks again for all your help.

 

Hip Hip Hurray!!!

It is now fixed. It took much longer than expected but it finally is fixed.

It turned out to be a couple issues which made it extremely difficult. The two relays were bad - for some reason over time and probably other things the relays went bad. I replaced the relays, the battery and then discovered the electric brakes were not connected with the breakaway switch correctly and fixed that. Then I decided to test and walla (sp?) the lights worked and I also got the test light on the brakes to blink which stopped for some reason previously. Then since everything was working I decided to run the internal lights directly from the trailer battery knowing the Expy will charge it (slowly).

In response to the trailer wiring (plug) - I know the converter that plugs into it does not have a center pin (it's just blank), and the rest of them I am unsure of.

The one I use for the boat - does have an active center plug which deactivates the surge brakes so it can be backed up. Not sure if that answers your question. I did find the tow package papers that explains the pin outs and relays if that is of interest?

But I appreciate all your help - especially the neg/pos reverse thing - thank you.