DIC (Driver Info Center) Display Brightness (lack of)

bankerjohn

Original poster
Member
Apr 21, 2012
8
Just bought a 2005 Trailblazer from my daughter ... and noticed that the DIC display is significantly dimmer than the transmission selector display directly above it. As a matter of fact, in normal daylight, it's rather difficult to read the DIC display.

Is this normal? or is the display not getting "full voltage" for some reason?

I assume there's no way to adjust the brightness.

Any ideas?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Welcome!

Those displays aren't the usual lamps, and need a local high voltage supply built into the gauge cluster. I can't be sure without taking mine apart again, but since the DIC is an option and all the gauges have the odometer, I'd guess they were built in separately to make them modular.

The brightness is not separately variable.

So assuming your daughter didn't give you an extended warranty :rotfl: the good news is that there are many repair shops to work on these, sometimes for a flat rate. Check Ebay or Google for "trailblazer gauge repair". The stepper motors often die on these depending on the vintage, but I think 2005 was after the really bad batch of gauge motors in the 2002-2004 time frame. If you had an earlier one I'd recommend you pay to get the stepper motors changed at the same time, unless you're good at soldering PCB components and can do it yourself later. The vehicle will drive just fine with the gauges removed to send out for the high voltage DIC display repair.
 

bankerjohn

Original poster
Member
Apr 21, 2012
8
After taking a picture of the display, it doesn't look quite as dim ... definitely dimmer than the transmission selector display ... but still readable. So I guess my question is more like ... is the DIC display usually dimmer than the selector display?

Here's what mine looks like:
 

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Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
I just went and checked mine and the PRND321 is slightly brighter than the DIC.

Have you tried using the interior dimmer switch to adjust it?
 

bankerjohn

Original poster
Member
Apr 21, 2012
8
Wooluf1952 said:
I just went and checked mine and the PRND321 is slightly brighter than the DIC.

Have you tried using the interior dimmer switch to adjust it?

No ... but it will be dark in another hour or so, so I'll check that then!
 

91RS

Member
Dec 4, 2011
105
I've not noticed if my old 02 was dimmer or not, but I just wanted to point out that you do NOT want to run the dimmer all the way up or you will start blowing the soldered in incandecant light bulbs in the cluster and all the switches.
 

bankerjohn

Original poster
Member
Apr 21, 2012
8
91RS said:
I've not noticed if my old 02 was dimmer or not, but I just wanted to point out that you do NOT want to run the dimmer all the way up or you will start blowing the soldered in incandecant light bulbs in the cluster and all the switches.

Is this a common problem with TB's ... or GM vehicles in general?
 

91RS

Member
Dec 4, 2011
105
bankerjohn said:
Is this a common problem with TB's ... or GM vehicles in general?

Common with GMs of the era. Delphi manufacturered almost all of the radios, clusters, etc. for GM and they used little incandecant bulbs in everything. I think they might be 12v bulbs and can't handle the 14.5 volts typically put out by the alternator. I keep my dimmer right where everything starts to dim and have had no issues. I haven't noticed this problem happening on the current stuff yet, I believe the lighting has switched to LED. However, I have still seen entire displays going out in clusters and radios a few times.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
91RS said:
I believe the lighting has switched to LED.
Our platform was used as a test bed for all sorts of semi-advanced ideas - many of them goofy. But there are TWO feed wires for dimmable lights in the dash and so forth. One for incandescent, and a separate one for the places were we had LEDs. The reason for the separate dimmable bus wires was the different PWM response curves of incandescent filaments (which rely on the thermal inertia of the lamp filaments to achieve perceived dimming) and LEDS (which turn on and off instantly and depend on human persistence of vision to give you perceived dimming).

For fun sometime, find a dimmed LED, like a tail light on a new car or an indicator on your cell phone, and scan your eye past it without blinking. You should see it as a dashed line of dots - that's the PWM signal turning the LED on and off faster than your retina can normally see. :wink:
 

SAR85

Member
Jan 31, 2012
74
I've noticed that the transmission indicator does not seem to dim with the other dash controls in my '03.

Edit: I checked this morning and it does dim, but is maybe slightly brighter than other cluster lights.
 

Mooseman

Moderator
Dec 4, 2011
23,918
Ottawa, ON
If it's more than just the base speedo, I do believe you can cycle through each display and one option is blank.
 

Lonestar245

Member
Sep 6, 2013
35
Sigh... 2009 Saab 9-7x. I have this same issue. The DIC lamps have grown so dim I can’t see them in daylight. They are fine at night when the headlamps come on. Normally they were brighter in the day, and dimmed at night. I have the dimmer knob rotated to maximum brightness, and it does work day and night, just not bright enough in the day.
All other lamps are fine- radio, HVAC, warning lamps, shift position indicator lamps, etc....
I’m guessing this has been fully addressed here, some sort of fault with the lamps or the voltage supplied to the lamps? Send the instrument cluster to a shop?
Or has there been new information uncovered?
I will add that sometimes my water temp gauge will instantly drop to “cold” - buried hard left and gauge warning lamp comes on. Then it MAY randomly reset itself. Or not. And if not, I can disconnect the battery momentarily and it will typically solve the problem. I have replaced the outside temperature sensor just because it was so cheap to do it and eliminate one possibility.
BTW- the camera makes the DIC look much brighter than it is. I’m also faced into the sun so the dash shadow helps. And the fact that it is running through test mode lighting all the lamps.9978B8C6-599C-4F61-9DE9-3F5F2FA791D9.jpeg
 

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