P R N D 2 1

I Have A Problem With My P R N D 2 1 On Dash Light Disappearing And Apprearing When It Wants To. I've Taken It In And It's Been Changed Out Twice And It's Still Doing It's Disappearing Act.

sounds like loose bulb or loose connection somewhere,

If it's a 99 or newer it could possibly be a problem with the nuetral safety/back up switch down on the transmission. Good luck.

If it's a 99 or newer it could possibly be a problem with the nuetral safety/back up switch down on the transmission. Good luck.

EXCUSE MY IGNORANCE, BUT WHAT'S THE NUETRAL SAFETY/ BACK UP SWITCH FOR.

It sends information to certain modules in the truck to inform them of what gear has been manually chosen by the driver with the shifter. It will turn the back up lights on in reverse, inhibit the engine from cranking over while in any gear other than park or nuetral, and it will send info to light the correct letter in the PRND32L indicator.

If you have allready fixed it, lets see if I'm right. I have a 99 Silverado with the exact same problem. What is happening is the power to the display is being interupted through the trip/re-set switch ( the small rod shaped plunger you depress to change from mileage to trip odometer). The display gets it's power through this switch. What you are pushing is just the plunger. It goes down and actuates the actual switch, which is a little square switch soldered to the printed curcuit board. It is about one quarter inch in diameter with a little red button in the middle of it. I've had my entire dash cluster out in my hands playing with it and was able to get the display to blink on and off while wiggling the switch with a screwdriver. Keep in mind I was allways aware of the other items on the PCB, as not to short out anything with the screwdriver--Be Carefull!! I do not know if just the switch is available or not. I have not fixed mine yet, as of this writing. I sprayed mine with some electrical contact cleaner and it seems to work a little better than it used to. Good Luck--Was I right??

Well, it only worked for about an hour. So, after talking with others, I came to the conclusion that it was a cold solder joint at the re-set switch. I removed the entire cluster from the truck, took it in the shop and hit the two points where the re-set switch is soldered to the pc board. It has been working fine ever since. Good Luck.

So what year is this vehicle, does your speedo and guages work when this happens?

Mine is doing the same thing, but there doen´st seem to be any cold solder, I tapped one node that had almost no solder on it and didn´t solve the problem, I may just touch it with the soldering iron to make sure it is not in an invisible part of the solder. Any more ideas???

Updatge:

Damned wire harness has a bad conection, anybody know which is the live wire for the lights? It can´t be the ground because the rest of the cluster works...Thanks!

Final update: Well.......after I welded the No 3 pink terminal, the no 5 black/white terminals (power and ground to the message center, clock, odometer and trip odometer, disassembled the terminals from the wire harness to check for continuity (I scared myself to death, took two wires out of the female conector and almost mixed em up); finally the trouble is the internal PCB behind the green screen, it moves up and down 3-5mm!! there is a cold solder but I can´t get to it, cause I may break the whole PCB and then I´d really be scrubbed. What I did was to jam a tip of a pen cap ( the part that holds the pen to your shirt pocket) between the two PCBs, turned the hot silicone gun on and siliconed the heck out of the corners, pen cap, and anywhere there could be movement, it was not pretty but it is working again, and I think it is better than to risk breakin the whole cluster.