Beware!! How to avoid trailer Fire!!

[ronaldo]

Beware!! There is a big probability you can propogate a fire to your trailer if you draw large amounts of current when you are connected electrically to your tow vehicle but not to your hitch frame to frame, and only if the ground white wire is too small to carry the current demand for the trailer and also if it is not properly centrally grounded..

I have fixed a couple of trailers, where the camper is left parked, unhitched, and they only connect electrical connector close enough for connection, for quick disconection for a trip to an errand. If the camper demands large current draws, your small gauge wire will over heat and melt and short with other wires running in wiring harness. I have seen two case where ground white wire is a 14 awg,, toast..

If the the draw demands comes when you are properly hitch, the frame will take the load.

If you connect unhitched, and dont have large current demand you are ok.

I solved this with a number 8 AWG from tow connector to central ground point to frame where all heavy ground loads connect to the same point. Ring terminal crimped and solder filled to avoind any resistance or voltage drop..

[Miriam C.]

8??? you must pull a lot of current! I totally agree with grounding to the frame with a larger wire..Actually I have every 12volt grounded to the frame separately along with the normal ground.

[Dale M.]

Current (no joke) wisdom here is ground conductor should be same size or larger (in wire gauge) than "Battery" (12 volt) conductor....

Also consider lighting load (marker-tail-stop-turn) while towing and battery charging..... (Yes all loads are cumulative when selecting wire gauge)...

Never depend on mechanical connection of hitch...

Dale

[Wobbly Wheels]

Ran across this and had a question.....

If your power wire is 14ga, how do you generate MORE current on the outgoing ground than the incoming power lead can provide ?

Is the battery giving it a little extra kick ?
Personally, I wouldn't feel comfortable towing a trailer with the battery via a battery switch. It can still charge while you're running but can't power the main bus.

The power line to the trailer should have blown its fuse/breaker long before the ground wire was in any danger.

Unless I've misread you, running 8ga for the ground just hides the problem rather than solving it.

While I do agree that the ground conductor should be larger, a 12Ga should be more than enough - the ampacity of a wire increases exponentially as the cross-sectional area increases.

All that said, what loads do you have that max out a 14ga wire ?

Again, apologies if I've misread or misunderstood the problem, I've been known to do that !

[Larwyn]

Maybe I'll just pull my battery out of the TD and send it back to the factory to assure that it is safely and properly recharged. Why take a chance on proven systems to work as designed?

[dh]

Funny, my hitch has a nice coat of black paint on it, so does the draw bar. I just checked with a meter, one lead on the hitch ball, one lead on the ground stud on the 7 pin, what does the resistance read? ''OL''. Also, if the trailer coupler is bolted on I would not consider that a good electrical connection either unless it was bolter on before getting painted.

[Larwyn]

Funny, my hitch has a nice coat of black paint on it, so does the draw bar. I just checked with a meter, one lead on the hitch ball, one lead on the ground stud on the 7 pin, what does the resistance read? ''OL''. Also, if the trailer coupler is bolted on I would not consider that a good electrical connection either unless it was bolter on before getting painted.

An even better test would be to read the DC voltage from the tongue of the trailer to the hitch on the tow vehicle. If that white wire is not connected on both ends you will probably read several volts. If there is a good ground either through the hitch or the wire you will read zero volts. Voltage drop is actually a more reliable way of checking for less than perfect connections.

[dh]

Funny, my hitch has a nice coat of black paint on it, so does the draw bar. I just checked with a meter, one lead on the hitch ball, one lead on the ground stud on the 7 pin, what does the resistance read? ''OL''. Also, if the trailer coupler is bolted on I would not consider that a good electrical connection either unless it was bolter on before getting painted.

An even better test would be to read the DC voltage from the tongue of the trailer to the hitch on the tow vehicle. If that white wire is not connected on both ends you will probably read several volts. If there is a good ground either through the hitch or the wire you will read zero volts. Voltage drop is actually a more reliable way of checking for less than perfect connections.

Can't do that on any of my trailers, I like to avoid the bad ground blues, so NOTHING is grounded to the frame.

[Larwyn]

Funny, my hitch has a nice coat of black paint on it, so does the draw bar. I just checked with a meter, one lead on the hitch ball, one lead on the ground stud on the 7 pin, what does the resistance read? ''OL''. Also, if the trailer coupler is bolted on I would not consider that a good electrical connection either unless it was bolter on before getting painted.

An even better test would be to read the DC voltage from the tongue of the trailer to the hitch on the tow vehicle. If that white wire is not connected on both ends you will probably read several volts. If there is a good ground either through the hitch or the wire you will read zero volts. Voltage drop is actually a more reliable way of checking for less than perfect connections.

Can't do that on any of my trailers, I like to avoid the bad ground blues, so NOTHING is grounded to the frame.

Well, I guess that's one way to handle it.....

I always run both wires to the tail/brake/turn and side markers but by design many of them also ground to the frame through the mounting screws. I do not try to isolate the negatives from ground. You're way works too.

[eamarquardt]

An even better test would be to read the DC voltage from the tongue of the trailer to the hitch on the tow vehicle. If that white wire is not connected on both ends you will probably read several volts. If there is a good ground either through the hitch or the wire you will read zero volts. Voltage drop is actually a more reliable way of checking for less than perfect connections.

In order for there to be a voltage drop though, there has to be some current flowing (ie something has to be turned on in the trailer and powered from the tow vehicle like lights, brakes, or whatever). The higher the current (ie: the more things turned on) , the greater the voltage drop will be, and any problems will be easier to spot.

I once had a rear window defogger that wouldn't work. If I disconnected the leads from the rear window, using a high impedance digital meter, I got 12 volts when the defogger switch was turned on. When I connected the leads to the window there was no voltage drop/voltage present across the leads (one would expect to see 12 volts across the hot and ground leads if things were right) because all the voltage was being dropped at a bad connection up under the dashboard. Because a digital meter draws so very little current, with the leads disconnected there wasn't enough current flowing/draw by the digital meter to generate a voltage drop at the bad connection.

Cheers,

Gus

[ronaldo]

QUOTED ""Ran across this and had a question.....
If your power wire is 14ga, how do you generate MORE current on the outgoing ground than the incoming power lead can provide ?
Is the battery giving it a little extra kick ?
Personally, I wouldn't feel comfortable towing a trailer with the battery via a battery switch. It can still charge while you're running but can't power the main bus.
The power line to the trailer should have blown its fuse/breaker long before the ground wire was in any danger.
Unless I've misread you, running 8ga for the ground just hides the problem rather than solving it. """

On particular trailers, they run only a fused #8 black power cable feed from tow vehicle and rely on the hitch contact for the return circuit. IF you are not hitched but are connected electrically, a white wire which is also used for marker lights will take the load, and if you pull enough amperage, you will overheat that wire and messs up your wire harness if that white wire is not used exclusively for marker light but shares also frame ground.

Capish....? lol

[bdosborn]

Personally, I wouldn't feel comfortable towing a trailer with the battery via a battery switch.

Me either. Those pesky batteries always tear loose when you tow via the battery switch.


Bruce