When you are testing the radio voltage, where are you putting your meter black lead?

 

I’m talking about the relay for the headlights not the dash I’ve already done those. Most of the time I have the truck running but I couldn’t do that yesterday due to our child sleeping and it’s drinking gas right now really bad, that’s a work in progress.

 

I’ve used the original ground wire and I’ve also ran an alligator clip wire from the battery and I’ve used the bare metal (they all show the same results)

 

And the radio power is the only thing this shows up on? Have you poked around in the fuse box with the lights on to see if the problem is anywhere else? I am assuming if the ignition had the same problem the engine would stall when the headlights were pulled.

 

No I have not been able to do that test yet. My truck does have an ammeter.

It cuts the power with just parking lights on as-well. I WILL HAVE TO REVERIFY THIS TOMORROW (Messing with the **** again yesterday I did note that the dimmer **** turned far right I’m at little to no voltage tracking with the dash lights all the way left I’m getting 3 to 4v or a little over don’t quite remember, which is also turning the dash all the way bright. Going back to other comments, I think this wire is the backlight that you can dim for the factory radio. I totally forgot you could do that but at the same time I can use the PCV vacuum relay connector that powers on with ACC or run and it drops the voltage there too.) So wouldn’t that also rule out the dash power wire? There were also only two wires going into the radio for the power side and the other wires were the speakers. I will work on getting colors and pic

I’m planning on getting a new battery and having the truck running tomorrow to do the test on the ignition and getting a baseline on all test points. Fuse 11 does not drop power with the parking/headlight switch engaged it stays constant but it’s getting a drop at the radio.

 

Got to ask what made you check the voltage to find this?
And why with the motor not running?
Dave ----

 

I went to go for a ride after I put the new radio in and said well let’s make sure everything is still working. I don’t get to drive my truck a whole lot, and pulled the headlights on and radio went dead. It’s been an issue for about a month now so it’s not that it’s a brand new thing. I’ve been trying to find just a simple quick fix to get me by for the meantime but it seemed like I had a bigger problem so I hopped on here. And sense yall are making a big deal the truck was running at this point when I found the problem. I’ve done a lot of work tracing wires without motors running in the Army and found problems just fine. We just either go straight in or plug in a battery pack (our Teslas) and get to work

 

Still scratching my head on this one. My TheoryDuJour™ has changed, as these things are wont to do.

New problem, didn't happen until installing the present stereo, right? Take a look again at post #7 by Dave. I suspect the stereo itself is not properly grounded to the vehicle. Do you have a brand/model for this unit? I'd like to see a wiring diagram. Some units are grounded via an external connection, such as a screw for a ring terminal, or a tab for a spade terminal. Other units are grounded via a dedicated wire in the harness. No matter how it's supposed to be, let's see what might happen if the ground was missing or insufficient.

The parking light circuit consists of multiple bulbs in parallel. All of these bulbs together are enough to provide a marginal ground somehow through the stereo and it works. But turn on the parking lights and now you've got power instead of a marginal ground. No voltage difference, and voila, the stereo stops working.

You had mentioned measuring low voltage at some other points with the parking lights on. I'd suggest removing the stereo entirely and taking the same measurements again. Do you still get the low voltage with the stereo removed? I'm willing to bet not.

 

Ok now we know why you are doing what you are doing and I think Karl is on to the radio not being grounded right.
As he said it is grounding thru the dash light wire to the factory radio and as soon as you turn on the lights the radio stops as it no longer has a ground.
IIRC the factory radio grounds thru the radio body and there is a threaded stud for a brace off the back that goes to the fire wall stud.

As for the truck running I would never check voltages with out it running but that is me.
When you say it is 11.? volts if running the ALT should be putting out 13.5 to 14.5 volts and if you are seeing lower than 12 then yes I would start to look things over.
But I think it is the radio.

As for the head light relays.
They are only for the head light bulbs nothing else.
You unplug both head lights and plug in the relay plugs.
The trucks plugs then plug into female plug of the relay kit.
The kit has a fused wire that goes to the battery and another for ground, that is it.

When you turn on the head lights, switch all the way out, the switch sends a signal volt to the dimmer switch then to the relay.
The relay see this signal and make the connection from battery to head lights thru the new wiring of the relay kit.
So the only power going thru the head light switch for the head lights is only to close the relays and that cant be all that big compared to powering the light bulbs.

Power is still going thru the head light switch for the dash and running light but the 2 head light bulbs pull a lot of amps thru old wiring and switch.
Also over time the head light switch breaker (resetable fuse) gets weak and trips shutting off the head lights when you need them most in the dark!
Because you no longer have the head light bulbs pulling high amps thru the switch, remember the power is not going thru the relays, the breaker should not trip unless there is a short in the system.

The only bad thing about the relays is they use a smaller relay and sockets so if one goes bad it can be hard to find a replacement but you are not left in the dark.
Just unplug the plugs from the lights and the kits wiring and plug the trucks plugs back into the bulbs and you can drive on.
I had 1 go bad after I washed the engine bay and it filled up with water. I picked up 2 normal relays and pig tails.
I removed the wires from the plastic plugs and put the kits wires in the larger relay sockets. I have since remounted the relays so they dont fill with water.

Also the way I have the kit wires and the trailer brake wires run you cant see them unless you really look for them other than at the battery tie in.
Dave ----

 

I’m still keeping up with what everyone is posting, but work has been pushed back on the truck. We finally got a call to move to a bigger house on post so I’ll probably moving and unpacking for about a week and then I’ll be able to get back on the truck. Thanks everyone for all the help so far and I’ll see what all I can work out and get back to yall later 🫡

 

We will be waiting
Have fun with the move I did it 10 years ago from CT to NC, still have not got back on the project I was working on up there
Dave ----

 

Well gentlemen I had a quick minute to look at the truck and figured well let’s run a wire directly from the ground terminal and give a chance at picking the right ACC wire. FIXED IT!! That’s all it was, the ACC wire would read as a ground when I checked wires but when the lights were turned on it created a short for that circuit due to the old radio grounding itself to the bracket and not having a dedicated ground wire like I thought. I’m running a new battery due to the old one dropping a cel. Thanks for all input and dealing with my whirl wind of information. I often write how my ADHD mind thinks and it can get confusing, even for me.

Take away notes the old radio is INDEED grounded with the mount. Yellow with black stripes is the ACC wire. Blue with red is the dimmer wire. I will be looking into the relays for the headlights soon and again thanks everyone for helping out!! 🫡

 

Good to hear you got it fixed and letting us know what the fix was as many do not.
Dave ----