Running lights on ??

[Protagonist]

Originally Posted by AWCHIEF

Or you can go fancy and make up a wiz bang gizmo. They are a couple of companies that make the expensive gizmos. I made up a gizmo out of parts from around the shop. Spare 7 pin plug, few inches of wire, short length of PVC pipe and a fuse. I also have a flasher that can be put in line for roadside emergencies. Painted it orange because I had a can. Total cost zero.

The most elegant setup would be a separate 12v wire (with in-line switch and fuse) from the house batteries to the clearance lights (or preferably from the fuse block if you've got a vacant space to use in the fuse block), and a blocking diode (2 inputs, 1 output) so that even though you would now have two sources of power to the clearance lights, power from one source doesn't back-feed to the other.

This is pretty much the same thing that is done on some toads so that the car's built-in tail lights, brake lights, and turn signals can be powered either from the car when it's not being towed or from the motorhome through an umbilical while towing.

Not as quick or as cheap as using a fuse to jump across the 7-pin connector, but this is the way I'd do it if I was doing it.

[waninae39]

i have a garmin RV GPS. it supports the garmin camera

i plugged the camera 12V wires to light wires. Thus when i turn the lights on in the TV, the lights in the AS go on and so does the backup camera

thus i can see the backup camera when i drive now

[rafmudaf]

I have a 20 amp blade fuse connected to two wires. When I touch pins 3 and 4 of the 7 pin connector, the fuse blows every single time immediately. What gives? Is this somehow an indication of another problem?

[SteveSueMac]

Originally Posted by rafmudaf

I have a 20 amp blade fuse connected to two wires. When I touch pins 3 and 4 of the 7 pin connector, the fuse blows every single time immediately. What gives? Is this somehow an indication of another problem?

Not sure how you define those slots. When I’m looking at the plug with the notch at the top (not at the bottom) it’s the slots at what would be 11 and 1 on a clock face. I also use a 10A fuse and no problems. Not sure if you’re doing the same?

[rafmudaf]

Originally Posted by SteveSueMac

Not sure if you’re doing the same?

Yea, at this point, I'm not sure if I am either.

The photos attached are the 7 pin connector on my Airstream (no umbilical cord, just the adapter that goes into the junction box on the inside), the 20 amp blade fuse, and the wires I'm using to connect pins 3 and 4.

I'm touching the two pins circled in red so those are the ones at 1 and 11.

[SteveSueMac]

Interesting. Mine is an umbilical coming from the AS and is the female version that connects to the tabs (male version) from the truck. But those 2 seem to be the right ones.

We’ve now surpassed my level of expertise. That was quick! [emoji23]

I’m sure others will chime in.

On edit - your trailer looks older than mine (mine’s a 2012).

Here’s how mine is wired - perhaps yours is wired differently??

https://www.google.com/search?q=rv+7...iTJiKE0W3NU6M:

[rafmudaf]

Originally Posted by SteveSueMac

We’ve now surpassed my level of expertise. That was quick! [emoji23]

We're in the same boat!

I measured the voltage and get 13 V between those two pins. So I expect something to happen (brakes engage or a light to turn on) but I do not expect the fuse to burn out.

[Al and Missy]

In the newer trailers where the fuse scheme works to light the running lights, you would not have voltage present. You should see a low resistance connection that is the combination of the light bulbs.

Best bet is to try to find a wiring diagram for your trailer. It is clearly different from current models.

Al

[rafmudaf]

I'm working with a 1977 model, so it is certainly different than current models. I have the original documentation and the wiring diagram for the tow vehicle connector (7 pin) agrees with what I've seen on Air Forums: 12 V is at 11 o'clock and running lights are at 1 o'clock.

I don't truly understand how electricity works, but I do know V=IR. My voltage is known: ~12V (13.04 V) and the current is known to be greater than 20 A since the fuses I've blown are rated at 20A.
V = IR
I_fuse < V/R
20 A < 13 V / R
R < 13 V / 20 A

So if I understand this relationship correctly, something is pulling more than 20 A but there isn't enough resistance in the circuit? Does that mean its not properly grounded? Also, 20 A sounds like a lot for my DC circuit that only has lights and fans.

[Al and Missy]

Originally Posted by rafmudaf

I'm working with a 1977 model, so it is certainly different than current models. I have the original documentation and the wiring diagram for the tow vehicle connector (7 pin) agrees with what I've seen on Air Forums: 12 V is at 11 o'clock and running lights are at 1 o'clock.

I don't truly understand how electricity works, but I do know V=IR. My voltage is known: ~12V (13.04 V) and the current is known to be greater than 20 A since the fuses I've blown are rated at 20A.
V = IR
I_fuse < V/R
20 A < 13 V / R
R < 13 V / 20 A

So if I understand this relationship correctly, something is pulling more than 20 A but there isn't enough resistance in the circuit? Does that mean its not properly grounded? Also, 20 A sounds like a lot for my DC circuit that only has lights and fans.

Sorry, I was having a brain fade when I posted. You are correct that one of the pins you need to connect to is the trailer 12V line and the other is the running lights. Maybe your lights are drawing more than 20A. That seems unreasonable, but if some of the bulbs have been replaced with the wrong ones, it could happen. I have - 2 tail lights, 3 top rear clearance lights and 6 side clearance lights, for a total of 11 lights. They should be around an amp each, but if replaced could be more.

Al

[Al and Missy]

I just checked my trailer's bulbs. The 6 clearance lights draw about 3 amps total and the 2 tail lights draw about 1 amp total for a total of 4 amps. Yours should be similar.

Al

[azflycaster]

Be aware your neighbor may not appreciate your lights shining in their windows all night long. Please be considerate and unplug at bed time.

[rafmudaf]

Originally Posted by Al and Missy

I just checked my trailer's bulbs. The 6 clearance lights draw about 3 amps total and the 2 tail lights draw about 1 amp total for a total of 4 amps. Yours should be similar.

Al

This gave me the idea to remove all of my clearance lights and try again. With the five pairs of bulbs removed, it still blows the fuse.

[rafmudaf]

Ok so after some more reading on AirForums (https://www.airforums.com/forums/f37...-204668-2.html), I decided to test the continuity of both the positive and negative leads to the running light fixtures to the skin. As it turns out, both sides have continuity to the skin! So I think that means theres wire within the running light circuit that is shorted onto the frame or the skin.

Now, if that is indeed the case, why would that cause such a huge load?