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??

[ktmrfs]

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.

[YC_1]

Ditto on the fuse and sometimes a relay needed.

However, you need a voltmeter to check the voltage on the TT with the engine running a bit above idle. You should see 13.5 or more if the TT battery is close to full.

[donn0128]

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.