Heard Popping Under Dash After Key Removal

[Thomas1117]

Today I was doing a coolant pressure test on my 99 GMC Suburban K1500 (5.7L 350 Vortec). I know I was supposed to disconnect the battery beforehand but I've had issues with the terminals connecting properly in the past so I left it alone because I figured the vehicle was off and hadn't been driven in hours. I disconnected the two sensors attached to the air intake and removed the air cleaner assembly box so I could get a better view of my hoses.

At some point I got in and turned the key (not to start the car) just to turn the lights on, but I immediately noticed my heater was on and blowing (the sensors and assembly were still disconnected at this time). I quickly turned the heater fan off and turned the key back to the off position and removed it from the ignition. At that point I heard 3-4 very quiet popping sounds coming from inside the dash behind the steering wheel. I also noticed that I was able to remove the key from the ignition with it being in the back position (radio clock light still on), which usually isn't possible (I think?).

My question is, do you think the quiet popping sound was related to not bleeding the coolant system yet, an electrical short, or just air sounds due to the heater running briefly with the air intake assembly detached? I'm hoping I didn't inadvertently cause some damage to the electrical system. Based on the scenario I described above, would you be concerned about that? If so, what tests/troubleshooting should I do to double check? I'll be finishing the coolant leak repair in the morning (wound up being a busted heater inlet hose) and will know then whether the car still starts (usually does). In the meantime I'm still worried about what those little popping sounds might have been. Any input or opinions would be appreciated. Thanks

[It's Tim]

Sounds like multiple electrical issues, flood vehicle?

[Swimmer8366]

After assembled have you tried to duplicate these sounds?

 

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[Motor City Rick]

You will have engine codes for the sensor you disconnected in the air cleaner system. Button everything back up and run the truck a few times, did the noise come back???

[barry G]

You will have engine codes for the sensor you disconnected in the air cleaner system. Button everything back up and run the truck a few times, did the noise come back???

 

good idea.

these trucks also don't slam grounds like the past (96 onward). When you clean out the coolant you are changing a big electrical value.

 

quite a thinker, like today.

if it is all working, just monitor.