Accessing C8 Front Fuse Block

[John]

An excellent DIY thanks to “RussM05.” He started down this path to wire his radar detector. We expect an update on this thread as he progress.

Thanks RussM05!

[Teamzr1]

Instrument Panel Fuse Block

The instrument panel fuse block is behind the glove box.
The glove box can be accessed by unlatching the door damper and squeezing the pivot to release the damper ring.
Pull the glove box bin side walls in to release the door stops.
Then turn the door until the hinge hooks release from hinge pin.

To Access:

1. Open the top cover.
2. Remove the top cover by pushing inward on the latch.
3. Pull the cover upward.

To Install:

1. Insert the tabs on the back of the cover into the slots in the instrument panel.
2. Align the clip with the slots in the instrument panel.
3. Press the cover into place.

Fuses Usage
1 –
2 Front wiper
3 Cooling fan 1
4 –
5 Cooling fan 2
6 Front blower
7 Front lift/Automatic level control
8 Shifter interface board module
9 –
10 Display IP cluster/HVAC/Center stack Module
11 USB
12 –
13 –
14 Glove box
15 –
16 –
17 Remote function actuator
18 Front trunk release
19 Intelligent battery sensor
20 Exterior lighting module 1
21 Exterior lighting module 3
22 Exterior lighting module 4
23 Body control module 2
24 Exterior lighting module 6
25 Amplifier
26 Automatic occupant
sensing/Electric park
brake
27 Video processing module
28 Right headlamp
29 –
30 Sensing and diagnostic module/Automatic occupant sensing
31 Body control module 1
32 Column lock module
33 Data link connection/Wireless charging module
34 Telematics/Head up display
35 Horn
36 –
37 –
38 Front wash pump
39 Rear auxiliary power outlet
40 Performance data recorder/Center stack module
41 –
42 Theft deterrent
43 Left headlamp
44 Exterior lighting module 2
45 Power steering column module
46 Body control module 3
47 Exterior lighting module 5
48 Exterior lighting module 7
49 Body control module 4
50 Front auxiliary power outlet
51 –
52 Steering wheel control switch
53 Heated steering wheel
54 –

Relays Usage
1 –
2 Glove box relay
3 Horn relay
4 Front wash relay
5 Retained accessory power/Accessory relay
6 Front trunk release relay 1
7 –
8 –
9 Front trunk release relay 2
10 Wiper relay

[John]

Very useful and specific enhancements to this DIY. Thanks much Teamzr1.

[Ragtop 99]

Not the easiest fuse box to gain access too.

[Neil H]

Pretty easy, about 30 seconds to remove the glove box & there it is.
Usually that is where the cabin air filter is but now that is up by the battery -- even easier access.

[Teamzr1]

Not the easiest fuse box to gain access too.

A lot easier like some Caddies you have to pull the bottom part of the rear seats off

Not much easier for us ole folks like C5s where a fuse panel is hidden on the firewall right by A pillar in taking off the right floor hatch and
then having to bend up like a pretzel to get to the fuses

[Neil H]

And the pretzel thing is why many mechanics have ******ed shoulders, necks and backs -- yup, I've got all 3.

[Neil H]

OK, I will spell it out b-u-g-g-e-r-e-d.

[Wingnut]

Anyone tapped these fuses yet? Electrical system in this car is complicated and all these fuses seem hot (no “accessory”). Thinking of hard wiring dash cam and need both. Don’t want to mess with back fuse box between seats as its not designed well enough to access without risk of breaking.

[jackfrostpdx]

Don’t want to mess with back fuse box between seats as its not designed well enough to access without risk of breaking.

It's really not that difficult the access the rear fuse box and it has at least one open fuse you can tap for a dash cam. Hiding the wire might be a little tricky though.

[meyerweb]

Anyone tapped these fuses yet? Electrical system in this car is complicated and all these fuses seem hot (no “accessory”).

What do you mean by "no accessory"? There's accessory socket under the dash, below the glove box, which is only live when the ignition is on. And there are lots of fused circuits there that are only live when the ignition is on. You could use an "add-a-circuit" fuse tap to wire your dashcam.

And while I'm sure you know this, just in case: the 2LT and 3LT have built in dash cam functionality with the PDR. So does the 1LT if you order the IOT upgraded audio / PDR option.

[Wingnut]

What do you mean by "no accessory"? There's accessory socket under the dash, below the glove box, which is only live when the ignition is on. And there are lots of fused circuits there that are only live when the ignition is on. You could use an "add-a-circuit" fuse tap to wire your dashcam.

And while I'm sure you know this, just in case: the 2LT and 3LT have built in dash cam functionality with the PDR. So does the 1LT if you order the IOT upgraded audio / PDR option.

Currently using the PDR as a forward dash cam, but I want “parking mode” capability. I purchased a rear-view cam and tried to hard-wire via the forward fusebox using fuse tap pigtails (done this successfully in my other two cars), but my multi-meter shows all fuses hot (constant power) vs. accessory (ignition only power) and it needs both (plus ground). Weird. I rerouted for now using that “socket” under dash to power the rear dash cam, but no parking mode as that’s hard-wired with an additional battery-protection box. Looks like I’m headed for forward dash cam as well using a separate battery for parking mode as the PDR doesn’t do that. The C8’s battery seems to park itself under 12.5v and the minimum “battery protection” limit in parking mode hard-wire units is 12v, so probably not much power to keep that functioning for long anyway. If the car is parked for a few days and the charger is hooked up then, it takes an hour or so to show fully charged, which indicates the battery depletes faster than other cars.

I guess this car being so electrically complex and dependent doesn’t seem a good fit for this option like most other cars.

[meyerweb]

^^^ Seems really odd that circuits for things like the lighter socket, mirrors, wipers, etc. are always hot, since they don't operate if the ignition is off. Is GM switching the ground rather than the hot side? Do you get continuity between the ground side of the fuse sockets and a chassis ground when the car is off?

[Wingnut]

^^^ Seems really odd that circuits for things like the lighter socket, mirrors, wipers, etc. are always hot, since they don't operate if the ignition is off. Is GM switching the ground rather than the hot side? Do you get continuity between the ground side of the fuse sockets and a chassis ground when the car is off?

It does seem odd. I also used a circuit tester that illuminates when checking a “hot” fuse (vs. accessory) and the front box fuses (of workable amperage) all set it off. I notice when I open and close the door (no ignition or accessory selection), my rear dash cam turns on for perhaps 30-60 seconds along with other assorted vehicle activations like lights (depending on programming selection), etc.

This car seems to be a poltergeist when it comes to electrics. I’m leery of even tapping into the fuses now and that’s really the only option for a parking mode (hot dash cam either constant or motion-activated). A seprate battery for that function seems the safer bet as of now. Not an expert by any means, but cannot come to any other reasonable conclusion.

[meyerweb]

The C8 seems to go through a bunch of self-checks when a door opens. GM specifically says if you're doing brake work you need to disconnect the battery or the system could pressurize the brake system if you open a door.