Is my car delivering 12v during driving?

[jornvango]

I have a suspicion that my Chevy Tahoe isn't providing 12v ("aux") power to my trailer while towing through the 7 pin connector. Let me start by saying that I don't know much about electricity.

I bought an automotive circuit tester at O'Reillys. When I turn on the car and test each of the 7 pins with the tester, touching each pin (while someone hits the brakes or turns on the appropriate turn signal or running lights...) makes the tester light up.

There are a few that the tester does not light up:

- the pin for 'ground' (I assume this normal)

- the pin for electric brakes (I assume this is normal as we don't have an electronic brake controller in the Tahoe)

- the pin for 12v AX -> shouldn't this trigger the tester to light up??

[deltabravo]

donn0128 wrote:
GM products for many years have had a dummy fuse installed. It needs to be replaced with the correct 30A fuse in the under hood fuse box. Located on the drivers side fender. Look, bit I believe it is either #1 or #2 stud. Without it there is no power to the 7 pin.

And all the GM trucks I've had, the wire is never connected to Stud 1 or Stud 2, it's coiled up next tot he under-hood electrical center.

[jornvango]

Ok, mystery solved. I hadn't properly attached the red cable to stud 1. Once I did, the 7 pin worked as expected and the RV battery showed 14.3V.

Fingers crossed that it keeps working and that I didn't mess up anything else!

Thanks everyone for your help!

[jornvango]

The Chevy manual states that for both the RV battery feed and the trailer brake, the "fuses for these two circuits are installed in the underhood electrical center, but the wires are not connnected".

So, I found a coiled up red cable somewhere in the engine compartment. I didn't see a 2nd cable coiled up (which I was expecting to find for the trailer brake). The manual states that the battery feed cable is red, so that looked good to me. I attached it to "#68 stud 1 (40A)" and started the car. My test light at the 7 pin didn't show any power and the when I plugged in the RV, the RV battery didn't show any incoming power either. (it was at 12.9V as it should be fully charged)

Out of curiosity, I connected the cable to the stud next to it: "#63 stud 2 (30A)". I started the car and my test light at the 7 pin lit up for the "1 o'clock pin" which is the battery feed! I connected the RV and checked the battery: it was receiving 14.3V.

Per the manual, stud 2 is for "Trailer brakes". I don't get it. Does this mean it's working as expected??

P.S. The manual also states that "if charging a remote (non-vehicle) battery, press the Tow/Haul mode button. This will boost the vehicle system voltage and properly charge the battery". So, I guess we will keep the Tow/Haul button pressed in the Tahoe, even though our trailer is so light the Tahoe barely notices it's there so technically we don't need to push it for driving comfort.

[twodownzero]

theoldwizard1 wrote:

jornvango wrote:
I have a suspicion that my Chevy Tahoe isn't providing 12v ("aux") power to my trailer while towing through the 7 pin connector.

Once you get the fuse/dummy fuse/no fuse issue worked out, you need to know that you are likely just barely getting 12V on the "aux" pin. Not enough to properly recharge a battery in a trailer.

He will need a meter (not just a test light) to determine that. Check voltage at battery with the engine running and compare to the 7 pin at the bumper.

[theoldwizard1]

jornvango wrote:
I have a suspicion that my Chevy Tahoe isn't providing 12v ("aux") power to my trailer while towing through the 7 pin connector.

Once you get the fuse/dummy fuse/no fuse issue worked out, you need to know that you are likely just barely getting 12V on the "aux" pin. Not enough to properly recharge a battery in a trailer.

[jornvango]

Per the manualhttps://www.google.com/amp/s/www.autogenius.info/chevrolet-suburban-2012-2014-fuse-box-diagram/amp/, it appears the cable has to be connected to #68 stud 1.

Other than this, I don't see a reference to "Trailer Connector Battery Power".

Is there a fuse needed?

P.S. The manual says to "see a certified GM technician". In other words, give your car to a dealer for multiple days to do 5 minutes worth of work ... to fix something that you should have had in the first place since we paid for the "towing package". I don't remember the Chevy dealer having the option to order the towing package with everything hooked up. :M

[APT]

My 1999 F-150, 2003 F-150, and 2011 Suburban all came with the fuses and/or relays for both trailer brakes and 12V charging circuits uninstalled. They are inexpensive if lost. Not everyone tows and there is some risk to keeping those hot all the time for those who do not know what their purposes are.

[hotpepperkid]

SidecarFlip wrote:
Leave it to GM, the 'dummy' company....lol

As I remember my old 2000 Ford came that way. It required a relay and a fuse which was in the glove box. Why didnt the dealer install them, go figure.

[SidecarFlip]

Leave it to GM, the 'dummy' company....lol

[downtheroad]

Look here..fuse box under the hood, driver's side.
As posted by others, there may be a dummy in that stud.

[wanderingaimles]

After verifying the fuse check again on the plug.
Wiring should be like this

[jake2250]

https://youtu.be/UlEJWaahwpQ

[turbojimmy]

ktmrfs wrote:

donn0128 wrote:
GM products for many years have had a dummy fuse installed. It needs to be replaced with the correct 30A fuse in the under hood fuse box. Located on the drivers side fender. Look, bit I believe it is either #1 or #2 stud. Without it there is no power to the 7 pin.

x2. and many times this is covered in the owners manual in detail on how to enable the power. And in some cases there is a wire that will need to be connected to the appropriate stud. the wire is already in the harness, just taped up and not connected.

Also, in many cases the power is only applied when the ignition is in the run position. And in other GM vehicles it is hot all the time.

x1000

My Avalanche (should be identical to your Tahoe) was this way. There are instructions in the owner's manual regarding connecting this wire to the lug on the underhood fuse box. When I went to install my trailer brake controller I read up on what needs done to make sure everything works back at the connector. I got to work and quickly realized someone had already done it. And there was already a brake controller tucked up under the dash (I bought the truck used).

[jake2250]

There is also a wire that you need to connect to the 12v trailer power stud in front of that fuse block.
Google it!