Hi folks,

After getting back in the GV club, I've got a couple of little issues I'm working on. The main one immediately is that the backlight for the main driver console (housing speedo, rev counter, fuel gauge, etc) isn't working at all.
Interior lights are on, and varying the brightness dial doesn't make a difference (The interior lights work, and panel illumination for radio, heated seats, overhead console buttons, etc, all light up fine, so I know the 'overall' circuit is fine)

So, how difficult is it to change the bulb in the main console? Looks like it's a remove the whole panel job, but anyone got a howto or guide/exploded diagram that they can share so I can see how to get at it and get into it to replace bulb (or as I've had to do in the past, de-solder the old bulb and put in a replacement directly onto PCB)

Ta in advance.

 

Always good replying to yourself ;-) but slowly making progress.

I'm going to document how I took the instrument cluster apart for future reference, but in the meantime, I've taken the instrument cluster out and found a few strange things.

Firstly, there doesn't appear to be any bulb holders at all, this is exactly as it was when I removed from dashboard, so unless I'm mistaken not only do I not have any bulbs (or burnt out bulbs) I'm also missing the holders/fittings to put bulbs in. So any suggestions on that would be appreciated, i'm wondering if I can order some of the aftermarket LED illuminators that have the plastic mount already on them and just put them in.



Secondly, at the top of the cluster is a small block that sticks out, peeking inside it has a transformer and a few large capacitors. This has a connector along the top that was disconnected on mine when removed. First question, I'm assuming this should be plugged in. Second, anyone identify what this is used for or what it does? It seems to make no difference plugged in or not.
(Second thoughts was that it was the illumination power supply/resistor pack for dimming, however voltage was supplied to the bulb contacts regardless of if this was connected or not!)



What do you guys think?

 

I really must admit good reply to yourself. Your showing, like as if someone has been there, scratched their heads, and said to hell with it and chucked a handful out the window. Handful of what, looks like bulbs, holders and wiring. So unless you've a time machine or tartis to go back in time and catch what went out the window, we are waiting entrepidary (What) for your answer.

 

Haha, love the reply, a perfect explanation of what happened I reckon!

So yep, time to get creative, however I have found some bulb suppliers online that appear to stock the bulb along with the fitting:

R509TBL Dashboard Bulbs BX8. 5D 12V 1.2W T5W Blue Base



But stupid me, I didn't measure the dimensions of the hole, electrical contacts, etc (I did voltmeter them, so I know they hit 12v at full brightness and down to 3v at dimmest), so either I take a punt and get one to test or I go back and measure it.

 

How about going to a breakers and get what all missing...

 

Those pics in #2 look like all the bulbs have been pulled by someone. The PCB might have a voltage regulator built into it and power is supplied from the PCB to the shoulder of the correct twist in bulbs. I've seen it before, not on a GV - but can't REM where mate.

 

They are PC74 bulbs. You need 8 of them total.

 

SMD replacement bulb[ does not state lumen - but a No: 2 is stamped on the bulb head]
LED replacement festoons [I put in a much higher powered version of the same thing]

I've never done my dash, but have done all the other internals and decided very early on that I wanted at least twice the power for the (1) map / festoons and a need to be very careful not to be too bright for the (2) dash.

 

Two issues. The reason I am pointing them out is because I was going to do LED's in ours also, but here are the issues;

1) All LED lights available that I have found, in a PC74 setup, the maximum degrees of illumination are 120*. Meaning, you will potentially get spotty lighting due to this. You want something with 360* as optimum. Meaning it illuminates in all directions. Looking at the ones linked, I only see the LED at the end of the unit. This tells me that there is very precise beam of illumination leading to the spotty lighting. My guess is even less than 120*...

2) I don't know if you have the indiglo gauges (we do), or the green backlit like Dodge liked to use, This bulb you link above looks to be blue. Meaning it will have a blue'ish coloring to them, similar to a 5,000 - 6,000 kelvin color temp. This won't mix well with the green'ish coloring. Ultimately, you want something in the 3,000 kelvin range. 3k is considered "warm white" and the closest to the regular incandesant bulb originally in there. The cluster requires the plain "warm white" bulb because all coloring is handled by the diffuser and cluster back coloring.

Most manufacturer's do this. GM does. The Pontiac "Warm Red" isn't due to red bulbs! It is the color on the back side of the gauge face that is painted red. Otherwise it uses the same PC194 bulb a Chevy cluster does.

Anyway, the link above, other than listing "blue" doesn't give any other pertinant tech spec such as degrees of illumination or kelvin rating.

I looked mine up on SuperbrightLEDs.com

 

Thanks CMNTMXR57, some really good info in there.

In the end I just took the plunge before you replied and I went for:


10 Pcs Car T5 5050 SMD LED Bulbs PC74 Socket Panel Dash Lights Green

So will take a chance on those, and if all else fails at least I then have the plastic caps which I can then replace with regular bulbs.

One way or another it'll light up, and anything at the moment is better than nothing!