Edit: Sorry, links all died, here are the photos in no particular order: http://s831.photobucket.com/user/dy...er hard wire-LEDs C-K-R-V trucks 1973-1987 91
If this is of interest to you, bookmark it, I will just add photos/text to this post as I progress, which as with most things I do, will probably take a long time. This is a '90-91 cluster, but no reason this couldn't be done with earlier. Wiring is a bit different, speedo is different, but no real differences otherwise.
I am hardwiring the cluster due to the numerous problems caused by the flexible plastic circuit "board", and I'm sick of having the extra parts sitting there taking up space waiting for me to do something. Some may not consider it an issue worthy of this work, but I've had the cluster apart many times, increasing tension on the bulb sockets, straightening out the copper leads, making sure other contacts are good, etc. Done with that, it only works for so long.
Here is the plan: use common 12V +/- for all gauges and any lights that are NOT tied into the headlight switch. Use small multi-LED's siliconed or epoxied in place to replace the 168/194 bulbs. Use a 16 terminal Delphi GT150 connector to join the vehicle wiring to the cluster wiring. The LED's will have separate power/ground from everything else because to dim them, you need a PWM dimmer, and it must be connected to the + and - leads of the lights. If you don't want to dim them, +/- for everything could be common, as the LED's draw next to nothing.
Apologies for the picture clarity, it's a cheap cell phone. All I have to work with. Without further ado:
First strip the cluster down. You will need to remove all gauges, the spring loaded gauge terminals, bulbs, plastic circuit "board", etc. Make sure to remember where the bulbs came from, not all cluster bulb locations had bulbs in them. Headlight controlled bulbs are dimmed, so they must remain at least partially separated (whether + or -) from the high beam indicator, along with turn indicator bulbs, brake bulb, 4WD bulb, CEL bulb, and any other indicator light your cluster may have.
+,-,signal terminals on each gauge can be determined by tracing the plastic circuit board. I double checked I didn't get anything backwards, then used a sharpie to mark each terminal that was going to get a wire, with what the terminal needs to connect to (+,-,signal). If you have a hard time following a trace, use your sharpie to mark it every few inches until you find it's termination. The 1990/1991 circuit board is stamped with +/- and which gauge so it's real simple.
I used 4-40 nylon cap nuts (that's what I had on hand) to isolate any terminal on each gauge that is on a resistor...careful...one gauge this may be the -, another the +, another the signal wire. Note to self: always verify when working with electronics! As shown below:
If you look close at the gauge picture immediately below, the - terminal I marked does not have continuity with the gauge housing (this means if the ring terminal touches the housing, it's a short. Thats bad). Cut the top of the nylon nut off, then drill the nuts out to the proper diameter to fit the terminal. They were still tight enough to thread on, but that is not critical, they are acting as a bushing. They just need to space the ring terminal away from the housing. A 6-32 nylon nut would require no work I suspect.
With the nylon nut installed, the ring terminal can be installed (this is mocking things up). I used 6-32 nuts to secure the ring terminal, but the threads may be metric. They don't need a lot of torque, and they have pretty good thread engagement, so I am not real concerned with this. That nut will get a dab of loc-tite when I'm satisfied it all works. I may also "reverse" the ring terminals, and bend the wire end 90*, so that there is less chance it contacts another terminal, or the housing. We shall see. Hard to see, but this is the nylon spacer, ring terminal, and 6-32 nut on the - terminal.
For wiring, I've decided to make my life easier and keep weird solder joints to a minimum. Instead of a single wire off a central trunk to each gauge for +/-, I'm going to run a string, crimping two wires to each terminal, as pictured. Wiring is coated in flux before crimping, as they will get a dab of solder as well. Notice the shrink tubing. Install this before you crimp the wires.
After the soldering is complete, as much of the ring terminal as possible will be covered with shrink tubing, again to minimize shorting between terminals. Wiring inside the cluster can just lay in there, the LED's do not generate heat enough to be worried about it. Wiring on the back of the cluster (all lights, speedometer, instrument panel connector) will be secured to the back of the cluster with the 4-40 nuts/screws and cable clamps. With the right drill bit the 4-40's will thread into the cluster tight enough to not need the wrench on them. Used button heads because I had them, whatever you can get will work, but the button heads will keep clearance issues to a minimum, which is an issue with the electric speedometer.
I think I had a better idea for the electric speedometer wiring, but this is what I ended up doing. 1/16" drill bit, two holes through each trace (+, -, signal). The stuff drills really easy, so no worries about messing it up. Clamped a thin board in a vise, used that to back the circuit board as I drilled. Thread wire through both holes, twist it back on itself, then soldered the wire on itself and to the trace. I ran a piece of shrink tubing up the wire after this solder, which completely covers the wiring on the underside. Should prevent shorting between the terminals unless I do something catastrophically stupid. This is going to be tough to wire up. I will probably have to order a three terminal metri-pack connector to be able to remove the speedometer if necessary, later. Otherwise the soldered on wiring would make it a real pain to remove, along with the wiring harness itself. I used a four terminal metri-pack 150 connector assembly I found at the wrecking yard (available at Mouser too of course), with the proper terminals from Mouser. Buy a cheap metri-pack crimp tool, it makes it far easier and cleaner.
Edit: If you do this drilling, be careful and check your work. I thought the speedometer I used (it's a spare) was bad. After soldering it all up, I hooked it up to a battery, and nothing. Turns out the drill bit on ONLY the - terminal of the board cut the trace...no contact. Added a bit more solder, problem solved.
This shows how I am using the wire clamps with the 4-40 screws and nuts. 1/8" clamp works good for 3 wires, 3/16" better for about 5 wires at most. Obviously depends on the thickness of each wire. Note that the 4-40 nut uses the same driver as the screws that hold the cluster together and in place. Also, it makes far more sense to thread the drilled hole in the cluster (tap works very quickly/easily, but the screw will work in a pinch)...use the 4-40 screw as a stud, and the nut on whatever you can access.
This is how I routed the speedometer wiring. It could be shortened, but you need to make sure you have enough slack to pull the speedometer out enough to access the wiring in the rest of the cluster. Speedometer is on a separate plug so it can be removed without de-pinning it from the cluster connector.
Success on the LED's! Or so I think. 8 SMD LED's so lots of room for failures (which does happen, at least with some LED's). As far as I can tell, most multi-SMD bulb assemblies being sold now will continue to work if one (or more) of the SMD's fail, which is good for something you don't want to have to remove. With the cluster the way it is, one out of 8 SMD's failing is not going to be noticeable. Seller on ebay is "more-things" and here was the auction title "2X T10 W5W 158 168 194 501 White 8 SMD LED Wedge Light Lamp Bulb DC 12V New". I got lucky with these, the SMD circuitboard assembly is held in by the "legs" which are the +/-. I had some older ones that were glued in the housing, and even after removed not so adaptable to this project. With these, I will bend the legs flat, and it will be flat enough to be siliconed to the bulb housing. (note when looking for bulbs...most of the T10 LED's sold have the legs/wires coming out the base of the assembly. The T10's I previously purchased with the wires out the base were glued in place, the ones I just bought with wires coming out near the top are not glued in place, so much easier to deal with. I recommend purchasing one or two first, then buying the rest after confirming their construction. So cheap and free shipping, no downside to purchasing two, then buying 3+ later to complete the project)
I have changed my plan a bit, based on the fact that the indicator lights are separate. I will need to wire at least the feed side of the indicator lights individually...turn indicators, 4WD, brake, check engine, etc. Come to think of it, to keep the ability to change failed lights, or future mods, I will do all the dash lighting in the stock bulb holders/locations. Check engine (in my case) required a resistor in parallel with the LED (thats resistor to +/- of LED), it lights dimly when vehicle is running. (With help from Rampage and Fordum, proper resistor turned out to be a 1/4 watt 10K Ohm one)
Here is one of the "PC168" holder/bulbs disassembled, along with the LED. The white piece is the base of the LED. The bulbs/holder aren't supposed to come apart. Using jewelers screwdriver or something similarly thin and flat, from underside of holder push the tool up the "inside" of each brass leg, which will unlock the brass contact and bulb. The bulb leads are soldered to the brass pieces:
Here is the LED sitting inside the bulb holder. Almost a perfect fit in regards to diameter. I will use a tiny bit of epoxy to hold the LED in the holder.
Here is the back side of the bulb holder with the LED leads poking out the bottom. To get some strength here (so the LED leads don't take the stress) I plan on drilling another hole in the base of the holder, and soldering the wire to the bulb such that the solder joint is inside the holder. This way I can run the wires out the base of the bulb, and epoxy the wires to the base of the bulb holder.
This is the "finished" bulb holder from the back. Procedure after bulb holder is "empty" is this: drill another hole in base of bulb holder, next to the existing one. Run +/- wires through holes. Clip leads off of LED as close as possible while still leaving enough metal to solder to. In the case of the diode side, you might try pushing the diode back towards the circuit board that holds the LED's, to make it more compact. Careful, the solder could break on the LED, or the traces in the board could pull up. Everything is pretty fragile as it is small. Make sure to buy plenty of spare LED's, I had a couple of bad ones (no idea if soldering heat did it, or bad out of the box) and I know I ruined a couple with careless handling. Additionally, JB Weld (and most epoxies) is not designed to work on plastic, and does not hold well to the bulb holder or wires. I scored the plastic, but really need to buy some plastic specific adhesive. Filling the bulb holder cavity completely with regular epoxy would probably work as well, if the LED fails, you'll need to replace the whole thing anyway. Yes the LED's work, and no, the dimmer does not work for them. They are on or off, which is how LED's are expected to react with varying voltage. If you are able to control the voltage much more precisely, you WILL see a dimming effect, but that is not going to happen with our dimmer. This is why PWM is used.
Here is a video of the cluster with the PWM dimming working. I have not painted the inside of the cluster with chrome paint, so the only difference from the stock cluster, is the LED's.
Video of the PWM dimmer in operation.
Here is what I did to join the wiring for the LED's. I will do the same for all the indicator light grounds as well, since I won't be dimming them I can't have the lights and gauges/indicators share the same ground. Obviously now done they have srhink tubing over them. This is just the "crush sleeve" used in various splices, I have some that are worthless as made, but work great for this. Cut insulation, pull out, ready to use!
Wiring "pinout" for the gauges is this, based on the '90 or '91 cluster PCB I have...I believe at least all 80's early 90's gauges are wired the same, never had a problem swapping them. *All as you are looking at the back of the cluster with the gauges installed*.
Left side, fuel: Left pin signal. Bottom pin -. Right pin +
Right side, top left, oil: Left pin signal. Bottom pin -. Right pin +.
Right side, top right, voltage: bottom pin +. Right pin -.
Right side, bottom left, temp: left pin +, top pin -, right pin signal.
No clock on the later cluster.
Hit an image limit, Part 2 is below.
If this is of interest to you, bookmark it, I will just add photos/text to this post as I progress, which as with most things I do, will probably take a long time. This is a '90-91 cluster, but no reason this couldn't be done with earlier. Wiring is a bit different, speedo is different, but no real differences otherwise.
I am hardwiring the cluster due to the numerous problems caused by the flexible plastic circuit "board", and I'm sick of having the extra parts sitting there taking up space waiting for me to do something. Some may not consider it an issue worthy of this work, but I've had the cluster apart many times, increasing tension on the bulb sockets, straightening out the copper leads, making sure other contacts are good, etc. Done with that, it only works for so long.
Here is the plan: use common 12V +/- for all gauges and any lights that are NOT tied into the headlight switch. Use small multi-LED's siliconed or epoxied in place to replace the 168/194 bulbs. Use a 16 terminal Delphi GT150 connector to join the vehicle wiring to the cluster wiring. The LED's will have separate power/ground from everything else because to dim them, you need a PWM dimmer, and it must be connected to the + and - leads of the lights. If you don't want to dim them, +/- for everything could be common, as the LED's draw next to nothing.
Apologies for the picture clarity, it's a cheap cell phone. All I have to work with. Without further ado:
First strip the cluster down. You will need to remove all gauges, the spring loaded gauge terminals, bulbs, plastic circuit "board", etc. Make sure to remember where the bulbs came from, not all cluster bulb locations had bulbs in them. Headlight controlled bulbs are dimmed, so they must remain at least partially separated (whether + or -) from the high beam indicator, along with turn indicator bulbs, brake bulb, 4WD bulb, CEL bulb, and any other indicator light your cluster may have.
+,-,signal terminals on each gauge can be determined by tracing the plastic circuit board. I double checked I didn't get anything backwards, then used a sharpie to mark each terminal that was going to get a wire, with what the terminal needs to connect to (+,-,signal). If you have a hard time following a trace, use your sharpie to mark it every few inches until you find it's termination. The 1990/1991 circuit board is stamped with +/- and which gauge so it's real simple.
I used 4-40 nylon cap nuts (that's what I had on hand) to isolate any terminal on each gauge that is on a resistor...careful...one gauge this may be the -, another the +, another the signal wire. Note to self: always verify when working with electronics! As shown below:
If you look close at the gauge picture immediately below, the - terminal I marked does not have continuity with the gauge housing (this means if the ring terminal touches the housing, it's a short. Thats bad). Cut the top of the nylon nut off, then drill the nuts out to the proper diameter to fit the terminal. They were still tight enough to thread on, but that is not critical, they are acting as a bushing. They just need to space the ring terminal away from the housing. A 6-32 nylon nut would require no work I suspect.
With the nylon nut installed, the ring terminal can be installed (this is mocking things up). I used 6-32 nuts to secure the ring terminal, but the threads may be metric. They don't need a lot of torque, and they have pretty good thread engagement, so I am not real concerned with this. That nut will get a dab of loc-tite when I'm satisfied it all works. I may also "reverse" the ring terminals, and bend the wire end 90*, so that there is less chance it contacts another terminal, or the housing. We shall see. Hard to see, but this is the nylon spacer, ring terminal, and 6-32 nut on the - terminal.
For wiring, I've decided to make my life easier and keep weird solder joints to a minimum. Instead of a single wire off a central trunk to each gauge for +/-, I'm going to run a string, crimping two wires to each terminal, as pictured. Wiring is coated in flux before crimping, as they will get a dab of solder as well. Notice the shrink tubing. Install this before you crimp the wires.
After the soldering is complete, as much of the ring terminal as possible will be covered with shrink tubing, again to minimize shorting between terminals. Wiring inside the cluster can just lay in there, the LED's do not generate heat enough to be worried about it. Wiring on the back of the cluster (all lights, speedometer, instrument panel connector) will be secured to the back of the cluster with the 4-40 nuts/screws and cable clamps. With the right drill bit the 4-40's will thread into the cluster tight enough to not need the wrench on them. Used button heads because I had them, whatever you can get will work, but the button heads will keep clearance issues to a minimum, which is an issue with the electric speedometer.I think I had a better idea for the electric speedometer wiring, but this is what I ended up doing. 1/16" drill bit, two holes through each trace (+, -, signal). The stuff drills really easy, so no worries about messing it up. Clamped a thin board in a vise, used that to back the circuit board as I drilled. Thread wire through both holes, twist it back on itself, then soldered the wire on itself and to the trace. I ran a piece of shrink tubing up the wire after this solder, which completely covers the wiring on the underside. Should prevent shorting between the terminals unless I do something catastrophically stupid. This is going to be tough to wire up. I will probably have to order a three terminal metri-pack connector to be able to remove the speedometer if necessary, later. Otherwise the soldered on wiring would make it a real pain to remove, along with the wiring harness itself. I used a four terminal metri-pack 150 connector assembly I found at the wrecking yard (available at Mouser too of course), with the proper terminals from Mouser. Buy a cheap metri-pack crimp tool, it makes it far easier and cleaner.
Edit: If you do this drilling, be careful and check your work. I thought the speedometer I used (it's a spare) was bad. After soldering it all up, I hooked it up to a battery, and nothing. Turns out the drill bit on ONLY the - terminal of the board cut the trace...no contact. Added a bit more solder, problem solved.
This shows how I am using the wire clamps with the 4-40 screws and nuts. 1/8" clamp works good for 3 wires, 3/16" better for about 5 wires at most. Obviously depends on the thickness of each wire. Note that the 4-40 nut uses the same driver as the screws that hold the cluster together and in place. Also, it makes far more sense to thread the drilled hole in the cluster (tap works very quickly/easily, but the screw will work in a pinch)...use the 4-40 screw as a stud, and the nut on whatever you can access.
This is how I routed the speedometer wiring. It could be shortened, but you need to make sure you have enough slack to pull the speedometer out enough to access the wiring in the rest of the cluster. Speedometer is on a separate plug so it can be removed without de-pinning it from the cluster connector.
Success on the LED's! Or so I think. 8 SMD LED's so lots of room for failures (which does happen, at least with some LED's). As far as I can tell, most multi-SMD bulb assemblies being sold now will continue to work if one (or more) of the SMD's fail, which is good for something you don't want to have to remove. With the cluster the way it is, one out of 8 SMD's failing is not going to be noticeable. Seller on ebay is "more-things" and here was the auction title "2X T10 W5W 158 168 194 501 White 8 SMD LED Wedge Light Lamp Bulb DC 12V New". I got lucky with these, the SMD circuitboard assembly is held in by the "legs" which are the +/-. I had some older ones that were glued in the housing, and even after removed not so adaptable to this project. With these, I will bend the legs flat, and it will be flat enough to be siliconed to the bulb housing. (note when looking for bulbs...most of the T10 LED's sold have the legs/wires coming out the base of the assembly. The T10's I previously purchased with the wires out the base were glued in place, the ones I just bought with wires coming out near the top are not glued in place, so much easier to deal with. I recommend purchasing one or two first, then buying the rest after confirming their construction. So cheap and free shipping, no downside to purchasing two, then buying 3+ later to complete the project)
I have changed my plan a bit, based on the fact that the indicator lights are separate. I will need to wire at least the feed side of the indicator lights individually...turn indicators, 4WD, brake, check engine, etc. Come to think of it, to keep the ability to change failed lights, or future mods, I will do all the dash lighting in the stock bulb holders/locations. Check engine (in my case) required a resistor in parallel with the LED (thats resistor to +/- of LED), it lights dimly when vehicle is running. (With help from Rampage and Fordum, proper resistor turned out to be a 1/4 watt 10K Ohm one)
Here is one of the "PC168" holder/bulbs disassembled, along with the LED. The white piece is the base of the LED. The bulbs/holder aren't supposed to come apart. Using jewelers screwdriver or something similarly thin and flat, from underside of holder push the tool up the "inside" of each brass leg, which will unlock the brass contact and bulb. The bulb leads are soldered to the brass pieces:
Here is the LED sitting inside the bulb holder. Almost a perfect fit in regards to diameter. I will use a tiny bit of epoxy to hold the LED in the holder.
Here is the back side of the bulb holder with the LED leads poking out the bottom. To get some strength here (so the LED leads don't take the stress) I plan on drilling another hole in the base of the holder, and soldering the wire to the bulb such that the solder joint is inside the holder. This way I can run the wires out the base of the bulb, and epoxy the wires to the base of the bulb holder.
This is the "finished" bulb holder from the back. Procedure after bulb holder is "empty" is this: drill another hole in base of bulb holder, next to the existing one. Run +/- wires through holes. Clip leads off of LED as close as possible while still leaving enough metal to solder to. In the case of the diode side, you might try pushing the diode back towards the circuit board that holds the LED's, to make it more compact. Careful, the solder could break on the LED, or the traces in the board could pull up. Everything is pretty fragile as it is small. Make sure to buy plenty of spare LED's, I had a couple of bad ones (no idea if soldering heat did it, or bad out of the box) and I know I ruined a couple with careless handling. Additionally, JB Weld (and most epoxies) is not designed to work on plastic, and does not hold well to the bulb holder or wires. I scored the plastic, but really need to buy some plastic specific adhesive. Filling the bulb holder cavity completely with regular epoxy would probably work as well, if the LED fails, you'll need to replace the whole thing anyway. Yes the LED's work, and no, the dimmer does not work for them. They are on or off, which is how LED's are expected to react with varying voltage. If you are able to control the voltage much more precisely, you WILL see a dimming effect, but that is not going to happen with our dimmer. This is why PWM is used.
Here is a video of the cluster with the PWM dimming working. I have not painted the inside of the cluster with chrome paint, so the only difference from the stock cluster, is the LED's.
Here is what I did to join the wiring for the LED's. I will do the same for all the indicator light grounds as well, since I won't be dimming them I can't have the lights and gauges/indicators share the same ground. Obviously now done they have srhink tubing over them. This is just the "crush sleeve" used in various splices, I have some that are worthless as made, but work great for this. Cut insulation, pull out, ready to use!
Wiring "pinout" for the gauges is this, based on the '90 or '91 cluster PCB I have...I believe at least all 80's early 90's gauges are wired the same, never had a problem swapping them. *All as you are looking at the back of the cluster with the gauges installed*.
Left side, fuel: Left pin signal. Bottom pin -. Right pin +
Right side, top left, oil: Left pin signal. Bottom pin -. Right pin +.
Right side, top right, voltage: bottom pin +. Right pin -.
Right side, bottom left, temp: left pin +, top pin -, right pin signal.
No clock on the later cluster.
Hit an image limit, Part 2 is below.
Last edited:
