Instrument cluster overhaul
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[edit] Instrument Cluster Overhaul
[edit] The Problem
My van is an 86, and came with the instrument cluster with the big clock and no tach. Even though it has an automatic transmission, I wanted a tach, which I find helpful in climbing and descending mountains, etc. My cluster was generally falling apart. The worst situation was the deterioration of the connection where the cluster connects to the wiring harness. The cluster has a printed circuit on the back which consists of copper traces in a flexible plastic sheet. The connection to the wiring harness simply leaves the copper exposed and the connector contacts these exposed conductors. Over the years the copper starts to corrode and sometimes peel off the plastic where the connector attaches. Last time when I took the cluster out, I had to repair one trace, and knew the end was near. Replacing my brake master cylinder this spring required removing the cluster, and caused more damage at the connection. Plastic fatigue had caused several of the screw holes used to mount the speedometer and tach to the cluster shell to break apart.
[edit] Resources on Hand and Project Goals
I had a cluster from an 85 van that I have wanted to install for some time. I had plugged it in before, and found that it had a problem with the coolant level warning light constantly flashing. And the 85 doesn't use the dynamic oil pressure warning system that the 86 does.
My goal of this overhaul was to repair the broken plastic parts of the cluster, combine the 85 and 86 clusters so that I had a tach, retained the dynamic oil pressure warning system, and had a coolant gauge that didn't flash at me constantly. I also wanted to permanently eliminate the problematic connector between the cluster and the van's wiring harness.
The photos below are thumnails. You can see them larger by clicking them.
[edit] Procedures
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This is the shell of the 85 cluster with everything removed from it that could be removed from it. I had to use the 85 shell because it is set up to hold the digital clock at the center of the bottom. You can see where I have rebuilt 6 of the 8 locations where screws hold the speedometer and tach into the cluster. They had disintegrated. Before reassembling the cluster I carefully cleaned the shell and the gauge faces. I paid special attention to the clear plastic over the gauges. It makes a big difference in how nice the gauges look. When clean, they look so nice and clear and sharp and bright, it's like a new car! |
 | Here you can see closer how I rebuilt/reinforced the corners where the screws hold the tach in. I built little forms out of tape, then "poured" JB Weld to add material where there no longer was any. After it hardened, I drilled it for the screw holes. |
 | Here I had to do a little clearancing of my added material so the tach/speedo could fit properly. I also had to file down the hardened JB Weld to get the height to match the rest of the back of the cluster. |
 | This is half of the back of the tach assembly. You can see it is seriously cracked up. I repaired it with "Automotive Goop" on both sides. You can also see at the bottom, the area that holds the plastic printed circuit so the edge connector can try to connect with it. Also note there are supposed to be holes at the bottom corners where the screws hold the tach assembly to the cluster shell. Replacements had to be fabricated. |
 | There it is after repair and reassembly. See next photos for more detail. Upper right hole and slot is where the voltage stabilizer and its heat sink go. |
 | The "Automotive Goop" is an adhesive that is very willing to adhere to plastic, its strong, and retains a little flexibility when cured which makes it work well in this type of application. Small washer attached with JB Weld to replace the missing corner. More detail in next photo. |
 | I tried to build up enough JB Weld to give the washer as much support as possible. When assembling this piece to the cluster, I just barely snugged those screws in place. So far they are holding well. |
 | The temperature gauge. The one in the '85 cluster had the constant flashing LED syndrome. So I wanted to swap in the working one from the '86. The problem is that the face of the gauge is shaped differently. (By face I mean the black background with the white markings, that goes right behind the needle.) The '86 has a big square shape, where the '85 one, seen here, has the angled corners so it can fit down in the corner of the tach. So the face from the '85 had to be swapped to the guts of the '86 temperature gauge. Note the hole through the back of the gauge chassis, and the piece with the teeth just in front of it. This is used to adjust the where the needle reads on the gauge. Think your van is overheating? Just tweak the gauge lower! Just kidding... |
 | To swap the face from the 85 temperature gauge to the 86 temperature gauge the rivets had to be removed, and they weren't even in the same place on both gauges. So I did a lot of comparing and then glued the face on to the working gauge from the '86. |
 | This is the deterioration of the connector on the instrument cluster that I'm talking about. This is actually on the printed circuit from the '86, which was not used on my rebuilt cluster. The one on the '85 printed circuit was a little better, but was close behind this one on the way to failure. |
 | I scratched my head and contemplated a good long term solution to this connector problem for a long time. Since I have worked with computers for a while, I have a lot of various connectors laying around. I needed one with 14 conductors. I ended up using DB-25 connectors, which have been commonly used as parallel port connectors for printers. They have 25 conductors. I used the male end here to attach to the cluster and the female end to attach to the van's wiring harness. |
 | I just did a lot of following the traces on the plastic printed circuit to see where I needed to tap in with the new wires. The most difficult way to do this was to solder to the copper traces in the plastic printed circuit. I made a mistake that forced me to do this more than I needed to. In this photo you can see the printed circuit where it is attached to the back of the speedometer. The circuit board for the dynamic oil pressure warning system is located out of the frame to the upper right. The printed circuit is from the '85 cluster, which doesn't have the dynamic oil pressure warning system, so I figured I didn't need that part of it and cut off that section of the printed circuit. Turns out there are some traces that traverse that section of the printed circuit that don't have anything to do with the dynamic oil pressure warning system. So I had to replace those with the difficult soldering of wires to the copper traces. Here are some of them. I used a dab of glue to hold the wires in place after soldering them so they wouldn't stress the copper traces. |
 | This is the piece I cut off. D'oh! Do not do that. |
 | More Soldering to the copper traces in the area of the digital clock. Glue to stabilize them after soldering. |
 | This one on the back of the tach was a little easier because there was a terminal there. The plastic still melts very quickly. |
 | This is the connector for the dynamic oil pressure warning system. I just removed it from the '86 printed circuit and soldered directly to the terminals. Glue to stabilize them. It can still be unplugged from the circuit board for future service. |
 | These were the easiest soldered connections. Where I could pick up a trace here on the leads of these components, I did. This is in the area between the tach and speedo and it is normally under a black plastic cover |
 | These were the easiest connections to make. I think some were required because of my mistake in cutting off that part of the circuit board. |
 | Now this came out pretty nice. That's the old edge connector on the van's wiring harness that connects to the problematic connector on the instrument cluster. I decided not to cut it off in case I came across a pristine instrument cluster at some pont in the future and wanted to revert to the stock connector. Careful stripping, soldering and heat shrink tubing. |
 | This is the other end of those wires that I spliced into the wiring harness. They are connected to the female side of the DB-25 connector. |
 | The back of that connector. I used every other pin in most cases to give me more room to solder. You can see I bent the unused pins out of the way. Heat shrink tubing again. Because I rarely throw something away that might be useful later, I even had wires that were close to the same colors as the factory used. |
[edit] Follow Up
This overhaul has performed well. About a month after completing it, I had some erratic gauge behavior and found that some of the connections where the wires were clamped under screws were not tight. Once they were tightened, I have had no problems. It has been about 18 months and 5000 miles. The van is parked outdoors so has seen temps as low as 10F and as high as it gets when the van is parked in the sun on a 100F day.
Edwardm 21:53, 31 January 2008 (EST)
