question about amp draw from trailer.

[SSolderitch]

I have a utility tag with 11 incandesent lamps (parking & clearence) which are fused on the trailer. I blow fuses until I get above 15/20 amps. Then everything is ok. I have no way to measure it, my fluke meter stops a 10A. I burned up the 7 pin to 6 pin round adapter because of the internal 20 gauge wire (rated for 7 1/2A). I rewired with a heavy cord with 7 pin connector. the wires range from 14 to 10 gauge (?) they are robust. Do the bulbs really draw that much? I heard 1/2A to 1A each = 11A at most?



Trailer has a full size battery for the winch



next problem: I blew the 20A fuse in the pdc for the brake lights when towing. Is the prodogy controller the problem? What does 5 stop lights & 4 electric brake magnets draw? Again I can't measure over 10A. Replaced the fuse & truck brake lights are ok. I am hooking up trailer for state inspection on thurs.

 

[Gary - K7GLD]

As I recall, the brake magnets on our Kit 5er draw between 2-3 amps apiece max - and depending upon the size of various clearance and tail/stoplites, they will usually run 1/2-1 amp apiece.

 

[jelag]

We tow several trailers and have run a 8 gauge wire from the battery to the trailer connector in place of the factory 12+ wire... we've also installed an 8 gauge ground... at the truck battery we have a 40 amp fuse... . from the male trailer plug we've used the same gauge wiring to power the battery and keep it charged...

One of our trailers uses a hydraulic dump and this heavy connection keeps that trailer battery fully charged... .

On my 5er we used to have issues with keeping the batteries on the trailer fully charged and with this set up we're fine... .

On all our trailers we draw off the trailer batteries with a group of relays... using the 12+ as power to the relays and run clearance, turn, and backup lights from these relays... we have 50 watt bulbs for backups on the trailers...

We use the power from the truck through the trailer connector as the trigger for the relays... .

Since I own several trucks and several trailers this was a task... but in the long run we've had fewer problems... . BTW we don't use diode style stop/tail or clearance lights... here in winter weather snow that blows around on the highway will cover the lights and make them useless as the LED lights don't carry enough heat to keep the light clear... . the sealed units with bulbs always have enough heat to keep the lights clear...

Hope this helps... .

 

[BDaugherty]

Like Jelag said. You can buy a really nice fuse holder for a maxi-fuse at napa. Then you can run a 30,40,50,60 etc amp fuse for your trailer. Then run a 8-10 gauge wire to the 7 pin connector along with a ground of the same size. It would be best to run the ground all the way to the battery, otherwise you are loading the small chassis grounds.



The trailer brake circuit and the brake light circuit should be separate. As long as your brake controller is rated for the number of axles you have, the draw shouldn't be a problem. However, if you have already melted the factory connector, you may need to go back and rewire due to previous damage.



If you have too much amp draw from the marker lights in your trailer, try going back and changing the bulbs from standard incandescent to LED. If they use 1156 or 1157 style bulbs, you can buy exact replacements from most parts stores that use LEDs. It will cost a few $$, but you will have MUCH less amp draw.



Also, here's a guideline for how to figure out how many amps a device draws:

watts=voltsxamps or amps=watts/volts

for example: a standard 1156 bulb is 26 watts. @ 12 volts, that would be: 26/12=2. 16 If you figure that you will be closer to 14v with the truck running, that's 26/14=1. 85



Also, use this calculator:

Power Calculators for quick conversions.

 

[SSolderitch]

Just to clear a few things up

the 7 flat to 6 round adapter had a small gauge wires and only the park lamp feed got hot inside the adapter. Bad set up - the 6 pin came with trailer so I used the adapter (temp). The trailer had bad grounds on the stop lamps which I also fixed.

I rewired the trailer with a heavy duty 7 pin plug & cord - I purchased pre-made. I needed to loose the adapter and go with larger gauge wires. they work - just the fuse seem large to me.

I never had a brake fuse issus until now.

I never had a battery charge issue, winch (ramsey 5k) loads and unloads cars no problem.

I have all connections in a 4x4 junction box & terminal strip. That way I can add fuses & relays as needed by remapping the connections.

I have the back up lights on a relay so I can flip a switch to turn them on for additional load lights. even with no truck attached, because they rum off the trailer battery.

I think the prodogy can handle 6 or 8 brakes and I only have 4.

 

[jelag]

The wiring to the trailer connector on our trucks comes from the fuse panel and is separate from the wiring to the lights in the bed... We've never found these wires suitable for anything but to trigger relays... we've always upgraded both the 12+ and the 12- as mentioned above in my post... .

If you look at the actual diameter of the wire going to the factory connector I can't see how it can carry the kind of current they expect in a modern trailer... power to the battery, lights, etc...

In the same manner we've upgraded our trailers as well... .

We've had problems with trailer brake circuits in the past with some of the wiring going through the axle from one side to the other... . the wire can chafe on the inside of the axle and cause high current and blown fuses... so on all our trailers we have a trailer junction box, and wiring to the trailer axles that is outside the tube... .

We also use non-insulated butt connectors and shrink tubing... . we buy from Del City - Wiring Products and Professional Electrical Supplies a clear heat shrink tube that has an adhesive on the inside like what is used on water wells... this is a waterproof connection... .

We understand and use ohm's law and the use of a digital meter...

Your brake controller should be fine... its the connections that worry me... .

I can't comment on your 11 bulbs without knowing the part numbers... but if you have fluke meter you can measure the total resistance of the circuit and compute current... lets say for an example you do this and the current should be 6 amps but you keep blowing the 10 amp fuse... You have a portion of the circuit that might be grounded when the trailer hits a bump... . or if the voltage goes low, current flow increases with low voltage... .

Hope this helps. .

 

[Road Dog]

Marker lights are in the 2 - 4W range so 11 lights would be 44W or about 4A. The 1157 is dual filament and is about 4W + 27W. I think there's a short and if you pull all the bulbs you'll still draw current. Or a bulb has shorted. Or a filament in an 1157 has sagged and shorted against the other circuit but you'd see the weird light behaviour.

 

[SSolderitch]

It happened after a week of rain. Yes I may have to do the bulb pull, test and start adding them back in one at a time.



I solder & heat shrink everything I do.



I brake wires are as is from previous owner (with wire nuts). The brake wires were changed from inside the axles to outside. the trailer is a 1990. I guess it is time to rewire the rest and tackle the truck wiring also.