Convert The Gauge Bulbs To Led on a GMC Syclone
With the GMC Syclone and Typhoon (Sonoma GT too!) well into their 20s, the once new and bright illumination of the gauge cluster has now dulled and become a bit of a strain to read at night. With LED technology a standard in the auto industry nowadays, it would only make sense to make the jump to an LED upgrade for the gauge cluster and resist to urge to just replace with standard bulbs. Not only will your gauge cluster glow bright like new, but your night vision will also thank you! Original article and photography by Warren Bowley.
- Pick & Hook Set- This will help remove the factory bulbs from their holders.
- Standard tool set for removing gauge cluster from dashboard.
- Multimeter - Testing for positive and negative on bulb contacts.
Gauge cluster seems dull and not bright enough anymore.
Gauge Cluster Removal
To remove the gauge cluster housing from the dash, refer to this article. Once you have removed the cluster, please continue here.
Once your cluster is out, turn it over and take one of the illumnation bulbs out. You should have this:
The factory bulb connections are spot soldered to the holder. The red arrows show where the wire wraps over the metal contacts:
Use the pick set to break the wires free of the spot solder so you can remove the bulb. The red arrows show the wiring and where it was attached to the bulb holder.
Here is the bulb removed from the socket:
Repeat doing this for all of the illumination bulbs. Idiot bulbs come later.
Fitting the Illumination LED bulbs
The LED bulbs I bought are polarized. If you hook them up backwards, they won't light up. So you need to figure out which is the positive lead and the negative lead. I found that on mine there was a short lead and long lead wrapped around the bottom of the LED. On most of them (if not all), the short lead was the positive side. Red arrows show that one lead is shorter than the other.
Flip the LED over and this is the other side:
Unbend the leads so they point straight down. You can see the length difference between the two leads better here:
Here's a quick look at the light up:
Here's the basic way I test to figure out which is which:
Once you've determined which is positive and which is negative, make sure you install each LED into the socket the same way. On mine there was a PC194 and white line that I determined would be used for the positive side of the LED. Red arrow shows the line and you can see that the short positive side of the LED is installed on that side:
Now use the pick set to bend the wires over the blade contacts in the holder. Red arrows point to how I did it. I suppose you could solder them in place if you want, but I didn't need to. They were held in there pretty tight.
That's all there is. I marked the bottom of my bulb holders with a sharpie to show which side was positive. You will see later in this post why I did it. Repeat for all illumination bulbs.
Fitting the Idiot and Heater Control LED Bulbs
Idiot lights are a little different. The bulbs are spot soldered to a tab that slides into a slot on either side of the bulb holder. These are easier to get off than the illumination bulbs. To remove you just press down a tab and pull the bulb out of the socket. Below, the upper red arrow shows the tab you need to depress and the lower red arrow shows the spot solder.
Here both tabs have been pressed and the bulb is being pulled out. Red arrow points to the tab that the bulb is soldered to:
Once you get it out, break the wire holding the bulb to the tabs and you should be left with two tabs like this:
Here is what the idiot light LED bulb looks like. Red arrow points to the leads. One short and one long like the illumination LEDs.
At first I tried installing the bulb like the factory did, but I wasn't getting a good contact. So, what I ended up doing was re-installing the tabs into the bulb holder and then bending the leads on the LED so they would get pinched between the LED bulb body and the tab when installing the LED in the socket. Like this:
Blurry picture, but you get the idea of how to line up the leads:
Slide the LED back into the socket and then test and mark which side is positive and which is negative:
Repeat steps for the rest of the idiot light bulbs.
Installing LEDs back into the cluster
After installing the idiot lights back into the cluster in what I thought was the correct orientation, everything lit up EXCEPT the check gauges, check engine, and parking brake light. Turns out that I had the bulbs in backwards. Typical thinking is that you apply 12v to get the bulb to light up, but I think those gauges are grounded to get them to light up, so the bulbs had to be installed backwards.
Remember when I said to mark which side was positive and negative. If you did that, then the following picture will help you re-install the bulbs. Yellow arrows point to the side of the idiot light that is positive.
Here's the full cluster. Yellow points to positive side of LED in socket.
Reinstall Gauge Cluster
Reinstall your gauge cluster by reversing the steps taken to remove it. Reference this article for help.
AC Control LED Install
If you want to do the A/C controls, they will take the 1 SMD idiot light LEDs. If you bought the package I linked to you will have a bunch left over. The A/C control bulbs just pull out and are replaced with the LED (no pin bending or anything, real easy).
Dome Light LED Install
The dome light LED is straight forward. If you can't install that, sell your truck. Remove the cover, take out the old bulb, put in the new LED. Remember that these LEDs are polarized. I thought I had two bad right out of the package until I tried reversing polarity and they lit up.