Electrical/cluster short & 300 miles from home

[AK49BWL]

That is exceptionally strange, because Fuse 9 is what powers the park lights with the switch on. They should be off by ALL means when that fuse is blown, front AND rear. There is something else going on in that truck.

 

[Road Trip]

I appreciate all the replies guys!

This is a brand new issue since the front impact. I’ve no electrical gremlins of any sort before.

So, update-Based on Road Trips excellent research and summary I pulled the driver side park lamp and inspected what I could access. There is nothing in the vicinity showing damage. The real kicker here is that all lamps including turn indicators are working. Something I had failed to mention is that I had performed the 4 hi mod and headlight relay mod a couple years ago.

All this said, it is currently single digit temps out so unless anyone replies back urging me not to, I think we’ll get on the road and not use lights and turn signals.

To recap
all exterior lights work with blown fuse/fuse removed

Turning off lights, replacing the fuse with lights still off-nothing noticed with anything functioning abnormally

After fuse had been replaced, turn light switch to first setting for park only, fuse blows (audible without engine running) park lamps on

And continue to headlight setting, headlights come on

Since switching on the lights is when the fuse blows, I’ll just leave them off. And not use turn signals….

Damage is on hood, grille and bumper trim

Hello Bretcopsey,

Thanks for the detailed status update. It's a head-scratcher for sure. Of course
from previous reported behavior on other GMT400 trucks the exterior lighting
circuits are famous for back-feeding and other counter-intuitive behavior when a
ground is lost or similar electric power shenanigans.

So the parking lamps working when we think they shouldn't wouldn't surprise me.
To a troubleshooter, the exterior lighting circuits is a cross-connected analog
monster. :0)

****

Getting back to your situation. Given your recap, right now the problem statement
is best redefined as "Fuse 9 blows when the Light Switch is turned from OFF to park."

At this point everything else is educated guesswork until more troubleshooting can
be performed.

Given this, simply avoiding the use of the Light Switch and the turn signals for the
remainder of the trip should be enough to get you home. (Hmmm - jolt from impact
adversely affected either Light Switch itself or something having to do with the
backlight illumination for the instrument cluster? And the photo of your truck's
front this morning was much different than what my imagination had conjured up -- I had
guessed that a corner was all smashed up despite the Good Samaritan's best efforts
to the contrary.

****

So don't disturb that switch, leave Fuse #9 blown for extra insurance, and once you
get back home/the dust settles then it will be interesting to figure out exactly
where the sudden jolt caused a marginal component to fail.

Safe travels --

 

[Sean Buick 76]

Best of luck to get home safely

 

[bretcopsey]

Thanks! We’ve made it about halfway so far without issue.

 

[bretcopsey]

We made it home. Will update when I get it figured out, but may be a while before I have time to work on it.

 

[bretcopsey]

UPDATE

First I again want to say thanks for the help on this. I have spent some time going over everything and I feel a bit of a fool in that I had checked fuse 9, but also 14 and it was actually 14 that kept blowing. So, I had folks on a wild goose chase from that aspect.

I have stripped off the grille and went over all wiring-nothing appears pinched or damaged. I did note that the a/c condenser got bent in the collision, which means the grille was shoved into the oil cooler, oil cooler into condenser…no sign of leaks, but I may be replacing more than just the grille for piece of mind.

I then moved into the cab and stripped off the dash bezel, cluster, stereo and HVAC switch. With everything removed I was able to operate the headlight switch without blowing fuse 14. I then started adding components back one at a time. First back in was the HVAC control. With the HVAC fan switch in the off position, turned on headlight switch and blew fuse 14. I checked every bulb socket and was able to get a couple to seat a little better (these were also swapped out to LED a couple years ago) Replaced the fuse and tried again. Seems to have fixed it as the fuse didn’t blow and all lights are back. The fan switch being run through each setting also had no negative effect. Adding back the stereo and cluster also had no negative impact. So, at this time it seems my problem came down to a bulb socket in the HVAC control not being fully seated and the jolt from the collision was enough to cause it to come loose enough to trigger a short.

 

[Road Trip]

UPDATE

First I again want to say thanks for the help on this. I have spent some time going over everything and I feel a bit of a fool in that I had checked fuse 9, but also 14 and it was actually 14 that kept blowing. So, I had folks on a wild goose chase from that aspect.

I have stripped off the grille and went over all wiring-nothing appears pinched or damaged. I did note that the a/c condenser got bent in the collision, which means the grille was shoved into the oil cooler, oil cooler into condenser…no sign of leaks, but I may be replacing more than just the grille for piece of mind.

I then moved into the cab and stripped off the dash bezel, cluster, stereo and HVAC switch. With everything removed I was able to operate the headlight switch without blowing fuse 14. I then started adding components back one at a time. First back in was the HVAC control. With the HVAC fan switch in the off position, turned on headlight switch and blew fuse 14. I checked every bulb socket and was able to get a couple to seat a little better (these were also swapped out to LED a couple years ago) Replaced the fuse and tried again. Seems to have fixed it as the fuse didn’t blow and all lights are back. The fan switch being run through each setting also had no negative effect. Adding back the stereo and cluster also had no negative impact. So, at this time it seems my problem came down to a bulb socket in the HVAC control not being fully seated and the jolt from the collision was enough to cause it to come loose enough to trigger a short.

Hello again bretcopsey,

Really appreciate you coming back and clarifying what was failing on your recent trip.
By doing so, you just increased the value of this thread for future troubleshooters!

Now if someone is blowing fuse 14, they can search the forum for that, read your
request for help, the symptoms noted, and finally see this page. I particularly
like the fact that the "when to expect power on this circuit" balloon states,
"Hot with Headlight Switch in Park or Headlight." (Which perfectly matches when
this fuse was blowing on you with an audible pop.)

Good stuff. Personally I learned a lot from your skating rink incident.

You must be registered for see images attach

BTW, Congrats on tracking down & fixing this asap instead of just leaving the failure in place.

 

[bretcopsey]

Hello again bretcopsey,

Really appreciate you coming back and clarifying what was failing on your recent trip.
By doing so, you just increased the value of this thread for future troubleshooters!

Now if someone is blowing fuse 14, they can search the forum for that, read your
request for help, the symptoms noted, and finally see this page. I particularly
like the fact that the "when to expect power on this circuit" balloon states,
"Hot with Headlight Switch in Park or Headlight." (Which perfectly matches when
this fuse was blowing on you with an audible pop.)

Good stuff. Personally I learned a lot from your skating rink incident.

You must be registered for see images attach

BTW, Congrats on tracking down & fixing this asap instead of just leaving the failure in place.

Thanks Road Trip! Your profile name couldn’t have been more fitting for this experience!