HUD will not light up

The instrument cluster HUD and the instrument cluster HUD dimmer switch are both connected to the instrument panel wiring harness.
The instrument cluster HUD dimmer switch performs the following functions:
• Provides power to the instrument cluster HUD
• Varies the intensity of the display image
• Controls the motor driven mirror
• Varies the height of the display image

The HUD dimmer switch gets power from IP / IGN fuse -10 amp Fuse Block
Right side of the IP, in the IP compartment opening

The main fuse that controls the entire fuse box is what I found worked for me on my 2003 GMC Envoy. I accidentally touched my wrench to the left side of the fuse while hooking the negative up on my battery causing all my interior lights, radio, a/c etc. to not work. It's only $4.99 at advanced auto. Took me awhile after checking every damn fuse in the car and not finding anything. Hope this helps

Driver info. center . IPC/ DIC fuse 10 amp - under hood fuse box .

bim or DIM ? the dimmer switch ! Interior Lamps
The interior lamps consists of two groups, lamps that can not be dimmed and lamps that can be dimmed. This first group consists of lamps that may not be dimmed. This includes those lamps that may be manually turned on by placing the interior lamp switch to the DOME position, or by opening a door or a compartment:
• Door courtesy lamps
• Footwell courtesy lamps
• Instrument panel (I/P) compartment lamp
• Overhead console courtesy lamps
• Reading courtesy lamps
• Rear compartment courtesy lamp
• Roof rail courtesy lamps
• Sunshade vanity mirror lamps

Interior Lamps Dimming
This group of interior lighting includes lamps which may be dimmed. This group uses a combination of class 2 controlled illumination and incandescent lamps:
• Air temperature switch
• Cigar lighter lamp
• Door switches
• Driver information center (DIC) switch
• Headlamp switch
• Head-up display (HUD) switch
• Heated seat switches
• HVAC control assembly
• Instrument panel cluster (IPC)
• Memory function switch
• Radio
• Steering wheel controls
• Window switches
For the interior lighting to be dimmed the following conditions must be met:
• A low light level has been detected by the dash integration module (DIM)
• Headlamp switch is placed in to the PARK or HEAD position
• Ignition switch is placed in the ON position
Then all class 2 displays and all incandescent back lighting will be illuminated to the level set by the instrument panel (I/P) dimmer switch. When the I/P dimmer switch is moved from MIN to MAX, all class 2 displays and all incandescent back lighting respond from minimum intensity to maximum brightness.
The DIM supplies battery positive voltage to the coil side of the PRK LP relay in the rear fuse block.
When the I/P dimmer switch is moved from MIN to MAX, then the instrument panel module (IPM), W/CJ2, or climate control panel (CCP), W/C67, applies a message to the class 2 communication circuit to the DIM. The DIM then applies a ground to the park lamp relay control circuit. This energizes the PRK LAMP relay and allows battery positive voltage to be applied through the DIMR fuse to the DIM. The DIM then illuminates the following incandescent lamps through the incandescent dimming output circuit:
• Cigar lighter lamp
• DIC Switch
• Headlamp switch
• HUD switch
• HVAC control assembly
• IPC
• Radio
• Steering wheel controls
The DIM also applies a message to the following class 2 controlled illumination components:
• Drivers door module (DDM)
• HVAC control assembly
• IPC
• Radio
The DDM will then send a message through the simple bus interface (SBI) to the RH front door module (RFDM). The door modules will then illuminate the following components through the incandescent dimming output circuit:
• Air temperature switch
• Heated seat switches (W/KA1)
• Memory function switch (W/A45)
• Power door lock switches
• Power window switches
The ground for these components are provided from the DDM and RFDM.
The following components are grounded at G200:
• Headlamp switch
• HVAC control assembly
• IPC
• Radio
• Steering wheel controls
The following components are grounded at G201:
• Cigar lighter lamp
• DIC Switch
• HUD switch

FUSE PANEL LOCATION
The fuse panel is located in the engine compartment. A label on the inside of the cover lists the fuse amperage and circuits protected.
volvo 850 fuses fuse panel layout service repair manual
FUSE PANEL IDENTIFICATION
Fig. 1: Fuse Panel Identification
Courtesy of Volvo Cars of North America.
WARNING: Always disconnect battery ground cable before servicing "high-current fuses. It is recommended that "high-current" fuses be replaced by a qualified technician.
* 1 - 15 Amp
Fuel Injection, Distributor Ignition, Automatic Gearbox
* 2 - 15 Amp
Fuel Pump, Alarm System
* 3 - 10 Amp
Courtesy Lights, Oil Level Sensor
* 4 - Not Used (1993-95)
* 4 - 10 Amp (1996)
Electronic Start Inhibitor (Immobilizer)
* 5 - 30 Amp
ECC Blower (Speed 4)
* 6 - 25 Amp
Central Locking System, Alarm
* 7 - 15 Amp
Audio System (Amplifier)
* 8 - 25 Amp (1993-95)
Power Antenna, Trailer Connector
* 8 - 40 Amp (1996)
Electronic Start Inhibitor (Immobilizer)
* 9 - 30 Amp
ABS, Traction Control System
* 10 - Not Used (1993-95)
* 10 - 15 Amp (1996)
Heated Rear Seat (If Equipped)
* 11 - 30 Amp
Heated Rear Window & Side Mirrors
* 12 - 10 Amp
Brake Lights
* 13 - 15 Amp
Hazard Flashers, Headlight Flashers, Alarm
* 14 - 30 Amp
ABS, Traction Control System
* 15 - 10 Amp (1993-95)
Audio System, Courtesy Lights, Door Open Light, Trunk Light, Glove Box Light, Remote Control Central Locking System,
Oil Level Sensor, Seat Belt Reminder
* 15 - 10 Amp (1996)
Audio System, Courtesy Lights, Door Open Light, Trunk Light, Glove Box Light, Remote Control Central Locking System,
Oil Level Sensor, Seat Belt Reminder, Data Link Connector
* 16 - 30 Amp (1993-95) Accessories
* 16 - 30 Amp (1996)
Power Antenna, Trailer Connector, Accessories
* 17 - 10 Amp
Key Reminder
* 18 - 25 Amp (1993-95)
Heated Front Seats, Power Mirrors
* 18 - 15 Amp (1996) Front Fog Lamps
* 19 - 15 Amp
Left High Beam Headlight
* 20 - 15 Amp
Right High Beam Headlight, High Beam Indicator
* 21 - 15 Amp
Left Low Beam Headlight
* 22 - 15 Amp
Right Low Beam Headlight
* 23 - 10 Amp
Left Parking Light, License Light
* 24 - 10 Amp
Right Parking Light, Bulb Failure Warning Sensor
* 25 - 10 Amp
Rear Fog Lamps, Fog Lamp Indicator
* 26 - Not Used (1993-95)
* 26 - 25 Amp (1996)
Heated Front Seats, Power Mirrors
* 27 - 15 Amp
Back-Up Lights, Turn Signals
* 28 - 10 Amp
Cruise Control, Heated Rear Window, Seat Belt Reminder Light, Shiftlock, Bulb Failure Warning Sensor, Heated Rear Seat
* 29 - 15 Amp
ABS, Traction Control System
* 30 - 10 Amp
Cigarette Lighter
* 31 - 25 Amp
ECC, ECC Blower (Speeds 1-3)
* 32 - 10 Amp
Audio System, Remote Controlled Central Locking System
* 33 - 15 Amp (1993-95)
Power Seats, OBD Test Socket, Tailgate Washer/Wipe (Wagon)
* 33 - 15 Amp (1996)
Power Seats, Tailgate Washer/Wipe (Wagon)
* 34 - 25 Amp
Windshield Wiper/Washer, Horn, Headlight Washer/Wiper
* 35 - 10 Amp
Instrument Lights, Sun Roof, Traction Control System
* 36 - Not Used
* 37 - Circuit Breaker
Power Windows, Power Sun Roof
* 38 - Not Used
* 39 - Circuit Breaker
Drivers Power Seat
* 40 - Circuit Breaker
Passengers Power Seat
RELAY PANEL LOCATION
The relay panel is located at the left corner of the instrument panel.
i copied this off a volvo site Hope this helps

Which fuse ? Just to make sure you looked at the right one .
DISPLAYS fuse 10amp located in the I/P fuse block .
Do you know what DTC'S - diagnostic trouble codes are ?
DTC B3619
The HUD detects that the HUD change page switch signal circuit is low for greater than 15 seconds.
DTC B3634
The HUD detects that the HUD dimming signal circuit is low for greater than 15 seconds

Diagnostic System Check - Head Up Display
Install a scan tool.
Does the scan tool power up?
Go to Step 2
Go to Scan Tool Does Not Power Up in Data Link Communications
2
Turn ON the ignition, with the engine OFF.
Attempt to establish communication with the following control modules:
• Head Up Display (HUD)
• Instrument panel cluster (IPC)
• Powertrain control module (PCM)
• Driver information center (DIC)
• Radio
Does the scan tool communicate with the control modules listed above?
Your best bet , take it to a qualified GM service center .

Yes, there's a fuse box inside the hood for ac but there's one more in another fuse box inside the car for the ac control. Check the one inside first.

I've never seen this problem personally, but I'd start with just pulling the dash apart and checking the connectors. I'll bet both use the same wiring harness. Just follow the wires back from the DIC and look for any abrasions or issues.

The IPC displays the season odometer information from the BCM in the driver information center (DIC). The odometer will display an error if the IPC detects invalid odometer data from the BCM.
You'll need to find a 10 AMP fuse in the instrument panel cluster, follow this diagram t locate it: https://ricksfreeautorepairadvice.com/2003-chevrolet-silverado-fuse-diagram/

Here you go. Under hood fuse block
Ign. Fuse E
and
ipc/dic
both fuses are 10 amp
I hope this helps. Take care.