How to:Repair 240sx digital speedometer with HUD.

by Aaron Longenecker
Overview:
This repair focuses on trouble-shooting one specific component on the electronic module, a capacitor.That is the one thing that has failed in other units too.
Please note that this repair requires skill at soldering, a fine pointed soldering tip and a steady hand because the part that you will need to replace is a very small surface-mount capacitor in a rather tight place.IT CAN BE DONE!, we did it.
Also, I suggest that you have someone help you with this task.There are times when a second set of hands make certain things much easier and quicker.
You will be removing the electronic speedometer module and testing a specific capacitor by heating it with a soldering iron.If that part is at fault, you will disassemble the module, remove the faulty part, solder in a new one, retest and hopefully, reassemble the whole rig. This may sound extremely difficult, but it really isn’t, there are just a lot of steps.
Difficulty: ***
Time: 1-3 hours
Cost: less than $10
Tools:
- Screwdriver
- 14mm socket wrench and ratchet with extension
- Soldering iron (fine-tipped)
- Needle nose pliers
- Magnifying lense
Materials:
- rosin-core solder
- the smallest 50volt, 1uF, radial lead capacitor that you can find.Below are some possible part numbers:
Vendor- Phone – Part #
Electronics Express (800)972-2225 14ER0501U
Allied (800)433-5700 852-6604
Digi-Key (800)344-4539 P5563-ND
Procedure:
* remove the speedometer and gauge cluster
* disassemble the cluster
* test the speedometer module by itself as detailed in the THE TEST: section
* remove and replace the faulty capacitor
* retest module
* reassemble car
=CLUSTER REMOVAL=
There are several plastic moldings that must be removed to get to the gauge cluster. The molding that holds the headlight switches, etc., is the most difficult part.Remove all of the screws that hold it in place.The switches in that molding, to the left of the steering wheel, can remain in the molding.The switches on the right side need to be popped out of the molding.I had to get into a position so that I could see behind the molding and I used a flat bladed driver to push on the lower locking tab of each switch.Push the tab up toward the switch.The bottom of the switch will push out when the tab clears the molding.There is just enough cable to allow you to unplug the switch from the outside of the molding.
Once the switches have been removed from the right side, the steering column must be lowered to make room to remove the molding.There are 2 lower nuts and 2 upper bolts that secure the column.Once the column is loose, lower it only enough to get the molding out, block it to hold it there.Now, the molding around the cluster can be pulled out and swung to the left of the wheel.It can hang there on the wires.
Now remove the 3 screws that hold the cluster in place and pull it out. There are four cables that have to be unplugged.The two larger ones in the center of the cluster have locks on both sides that you squeeze to unlock.The plugs on the left which go directly into the speedometer, only have a lock on the right side.Once the four plugs are out, the cluster can be removed.
=CLUSTER DISASSEMBLY=
Detach the ground wire that is protruding through the back, right behind the speedometer module.Also, you will see a small plug toward the bottom side of the module that you need to unplug.
To access the speedometer module, split the cluster assembly by releasing the locking tabs on the back section.Once the cover section of the cluster is off, you will have access to the electronic module.At this point the other gauges will be exposed so be extremely cautious not to touch any of the needles, etc.
Remove the screws that hold the module is place and carefully slide it out.Once out, it is a good idea to snap the cluster back together to protect the other components.
=THE TEST=
Heat up your soldering iron.
Hold the module carefully and plug the two cables, from the dash, back into the module.Turn the ignition switch to the RUN position.The speedometer should still be dead (if not, then some other miricle has happened).Touch the tip of the soldering iron on the top of the small capacitor shown in Photo 1 (it looks like a tiny aluminum can).In just a couple of seconds, the speedometer should come to life and display a zero.Do not hold the iron on the capacitor for more than a few seconds (ten seconds max), it can make the entire board very hot.

If the display lights up, remove the iron and let the capacitor cool until the display goes dark, then try again to confirm.If this worked, the capacitor is the problem.Disconnect the cables from the module and go to ‘MODULE DISASSEMBLY’!
If the unit does not respond, be sure that you are testing the correct component.Reapply heat to the top of the capacitor.If still no response, apply heat to the other capacitors, one at a time.If still no response, then your problem is beyond the scope of this document.Sorry, go back to forum at NICOclub and look for a replacement in the Classified section.
=MODULE DISASSEMBLY=
Work on the module at a well lit bench or table.
To have better access to the faulty capacitor, disassemble the module. First, there is a plug at the end of the top board that must be unplugged. The top board has one screw at the end and two locking standoffs that must be released.Remove the screw. The standoffs can be released one at a time. Carefully squeeze the top of one standoff with needle-nose pliers (don’t scratch the board) and just begin to slide the board up.Move to the other standoff and release it.The top board should be free to pull off, it will pull a little hard because there is a connecting header that you are separating as you pull.
Remove the four screws to free the second board.There is a ribbon cable hard-wired to the bottom board so you will only be able to swing the second board to the side for access to the capacitor.
NOTE: The small board that the faulty capacitor is sitting on is at an inconvenient angle to its motherboard.When I bent it out to a more easily accessible angle, one of the connector pins broke loose from the board and I didn’t find it until my third attempt at the repair.So be extremely cautious about bending that board, some of those joints are almost impossible to get to for soldering.
=THE FIX=
You should now have access to the top of the capacitor.I know this sounds strange, but use pliers and pull the top of the capacitor off (the little aluminum can, it pulls off easily).There will be two, fine wires sticking straight up.
NOTE: Pay attention to the polarity of the new capacitor.Although the capacitor will probably work installed either way, the positive lead should be on the left side when looking at the board as in Photo 2.
You may try to solder the capacitor to these wires if you want.If you get a firm solder joint, great!It will work that way.As the forum posting that we read stated, you may want to secure the capacitor from vibration with a spot of hot glue.
I did not have success soldering to these wires.I had to cut the wires close to the base, remove the plastic base and carefully de-solder the leads from the board.Be certain that you remove all metal fragments that you de-soldered.DO NOT touch any other component with the iron while de-soldering and soldering on the board.When you de-solder the leads from the pads, there should be only a tiny amount of solder left on the pads.
Before trying to solder the new capacitor onto the board, bend and shape the leads so they are similar to the shape of the one in the photo.Do not attempt to solder the capacitor down and then bend it into position, the pads could pull off the board which would be tragic.
Test the spacing of the leads on the board before trying to solder.Be sure that they fit the pads closely, do not touch each other and do not cross or touch any other component or pad.When you have the leads shaped correctly, tin the leads with a minute amount of solder.Hold the capacitor in place and touch one lead with the iron.Keep the iron in contact with the lead only as long as it takes to melt the solder.When the first lead joint is solid, solder the second lead.Apply more solder if necessary, but not much.These pads are very close to non-connecting traces and a big blob of solder could risk having an electrical short.

(This photo shows the new capacitor installed)
Carefully inspect your work with a magnifying lens to insure that the joints are solid and are not overlapping other pads or traces.Also check for and remove any fragments of metal on the board.

(This closeup photo shows the capacitor leads and pads. As you can see, there is a big ball of solder on the left pad. I left it that way since it did not touch any other traces.)
=RETEST=
Completely reassemble the electronic module.As with the first test, hold the module carefully and plug the two cables, from the dash, back into the module.Turn the ignition switch to the RUN position.The panel and the HUD should light up and display a zero.If so, everything can be reassembled and you are ready for the road.Go to FINALLY.