Help Please - Fighting new Gremlins

[tj43]

My historically very-reliable Suburban threw me an electronic curveball today (and it may be my fault). I will endeavor to provide the full story, since I do not know what may or may not be important:

I installed some back up lights yesterday afternoon. It was pretty straightforward. The lights wire to a relay that I installed on the firewall. The relay gets its main power from the battery and grounds to the radiator support ground near the battery. The interior switch controlling the relay grabs switched power from an add-a-fuse tap on the main fuse panel in driver's footwell (cant remember which one--maybe the auxillary heat/AC?) and grounds back to the relay. So, the entire system only interfaces with the Suburban in 3 spots: (1) positive battery terminal, (2) ground bolt at the rad support, and (3) the add-a-fuse. The install was straightforward and uneventful.

However, after the install my radio (Retrosound) that has been working flawlessly for a year or so would not power up. The Retrosound is a little unique because it requires 3 items for power: (1) a ground which it gets from the radio harness, (2) switched power (also from the radio harness), AND (3) constant power. My retrosound gets constant power from another add-a-fuse on the horn circuit in the main panel. I assumed I had just bumped that when doing the back-up lights since it was the only thing in the vicinty of where I was working. I monkeyed with it, swapped a fuse and it worked again . . . for a while.

Fast forward to today and the radio stops working again. I hunt around under the dash for the better part of two hours trying to figure out the issue. Eventually, I assume the radio has simply died and I remove it entirely. My plan is to attempt to power it up on the bench later and, if that fails, call Retrosound next week to discuss warranty repair or replacement. I then go to drive the Suburban back to my shop tonight. I turn on the headlights and the following occurs: (1) brights are on when in the non-bright setting (they turn off in the "bright" setting), (2) both blinker indicators are constant on (unless I move the stalk in which case they blink with the indicators), (3) no instrument cluster lights at all, and (4) the gas gauge falls to empty. If I turn the headlights to "off" everything reverts to normal.

So, what on earth did I do? I double checked the ground at the rad support (since it was the only ground I messed with). It seems fine. I removed a couple of my add-a-fuses thinking maybe they were a problem, but that did nothing. What am I missing?

A couple random thoughts in my head: I wonder if the radio is fin and its loss of power is a symptoms of the same problem--I just didnt notice the larger issue yesterday or earlier to today since it was daylight and I had not used the headlights. Conversely, is it possible the radio is actually dead and simply having the radio disconnected (radio harness is dangling but not contacting anything) is causing all this other drama?
I need some direction and thoughts on where to troubleshoot from the GMSB braintrust. Thanks in advance.

 

[EvilGenius]

To me it sounds like a ground problem. As grounds degrade their current carrying capacity goes down. By adding your new rear light circuit you exceeded your current capacity for your grounds. Since then you're just playing whack-a-mole with what circuit has a good enough ground path to function.

My truck doesn't have stock grounds anymore so I'm not sure exactly how the factory grounds are, but I think the only ground connection to the battery is near the alternator bracket. If that's true that means all grounds for the whole truck go through the engine block. If the path between your new ground and that is rusty or just poor you're going to be having a bad time.

So to check your grounds go backwards from the battery. All ground connections have to return to the battery to complete the circuit. So clean the connection closest to the battery. Then go to the next connection in the chain from there. And so on. If that doesn't end up fixing things at least you'll have less problems in the future. Bad ground are probably something like 80% of all electrical problems.

 

[Jgonick]

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[Ricko1966]

Doesn't sound like a ground problem to me. Sounds like you added a circuit and are back feeding an existing curcuit. Put everything back like it was first. Is the problem gone? If so let's figure out where you went wrong adding a circuit and add one without backfeeding an existing circuit.

 

[tj43]

I completely unwired my new aux lights. No change.

New symptom: if I roll the dimmer knob all the way to the right (full dim) everything continues to work properly. If I give the interior lights any additional brightness, all the bad symptoms return.

 

[Ricko1966]

I completely unwired my new aux lights. No change.

New symptom: if I roll the dimmer knob all the way to the right (full dim) everything continues to work properly. If I give the interior lights any additional brightness, all the bad symptoms return.

Did you put EVERYTHING back like it was before you started? Did everything work properly before? It is very unlikely some new condition crept in all by itself coincidentally at tge same time you started changing things.

 

[tj43]

Did you put EVERYTHING back like it was before you started? Did everything work properly before? It is very unlikely some new condition crept in all by itself coincidentally at tge same time you started changing things.

Yes. I completely removed every connection the aux lights have to the truck (ground, hot at the battery, and hot at the fuse panel).

I agree that there must be some correlation. Need help brainstorming what it could be.

 

[Jgonick]

Just curious- what happens if you pull the 5amp INST LPS fuse?

Not at home- but if I’m remembering correctly- it goes to instrument panel lights & goes to radio (gry). Its feed by green from pull light switch. Just wondering if that’s the circuit that got messed up somehow

 

[tj43]

I replaced the headlight switch/dimmer. That did nothing.

So, I then lost my mind and pulled the whole dash and cluster. My initial thought was that the circuit board on the back of the cluster might be bad.

After pulling the cluster, I found this (photo attached). I assume this is a common ground for multiple items. It looks like I have one loose wire back there and there are a couple spade connectors dangling unhooked in the vicinity as well.

Does anyone know what two items should be connected to these spades, but aren’t? I’m really hopeful this is my issue.

I’m also about to go down a “while I am in there” rabbit hole with new dash speakers, new cluster lights, and a new light on the HVAC control.

 

[tj43]

Just curious- what happens if you pull the 5amp INST LPS fuse?

Not at home- but if I’m remembering correctly- it goes to instrument panel lights & goes to radio (gry). Its feed by green from pull light switch. Just wondering if that’s the circuit that got messed up somehow

I already had the cluster out by the time I read your post. Sorry. I’ll try it once I get everything back together. Thanks so much for helping me brainstorm. I really appreciate it.

 

[Jgonick]

If that is on the left kick panel- that is the main ground location for things inside the cab- definitely will cause problems if things are not grounded well there.

 

[sublimeobs]

Does anyone know what two items should be connected, to these spades, but aren’t? I’m really hopeful this is my issue.

That's the ground bus and there were a few "vacant" on mine, so you may not be missing anything.

 

[Jgonick]

Reread the whole thread- just wanted to confirm that you did check the main grounds? Especially the one on the radiator support & the main one running to battery.

 

[tj43]

Reread the whole thread- just wanted to confirm that you did check the main grounds? Especially the one on the radiator support & the main one running to battery.

I did. Triple checked. Cleaned all the terminals and bolts with a wire brush and contact cleaner.

 

[Jgonick]

I could be totally wrong, However, I still lean towards a ground problem like @EvilGenius pointed out. He described it very well.
Your turn signal indicators staying on when not in use is a very strong indicator. If the parking lights don't ground properly they back feed through the turn signal wire and go to ground at the turn signal indicator (making the indicator light up). The more things you have on (drawing current and trying to get back to the battery) the more stuff is wacky. I wonder if your main ground from the battery finally degraded enough to cause problems. Also if the cab ground is not good it can cause a lot of random things to happen when trying to find a path back to the battery.