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"Technica" Digital Dash Cluster Repair & Conversion


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Earlier this year, an '86 Starion showed up at the local Pick n Pull yard and I was thrilled to be able to pick up quite a few good parts off of it. One of the best pieces I was able to get was the digital dash cluster. Not knowing whether the cluster worked or not; the yard having a strict no-power-up policy flanked by a generous 30 day-return policy, I took a risk on it.

 

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When I removed the cluster, I also cut off the plugs with enough pigtail attached to work with.

 

Per information on this forum, I learned that these digital cars use a dedicated fuel tank sending unit and speedometer "pulse generator" so I also grabbed these two items.

 

Per the '86 Electrical Service Manual I made a crude color code diagram comparing the colors of the harness in the 86 with those of my '87. Many are a color-for-color match. Some are not.

 

For a basic bench powerup, I was able to apply 12 volts to only the cluster computer and the illumination circuit. Without the illumination, the LCD is mostly indiscernable.

 

What did I find? The cluster "lit up" but all of the LCD displays were blank. It was acting as if the cluster computer was DEAD. For all intents and purposes, it was... as when I traced the 12 volt B+ supply through the unit, only about half of the board was receiving power. It was also painfully clear to me that the board needed to be completely reflowed, as too much time in the sun caused nearly every one of the solder joints on it to crack out.

 

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Sure enough, after I resolved the power issue, the speedometer and other gauges were "intermittent" when I tapped around the back and edge of the cluster. Absolutely unacceptable.

 

Anyway, something interesting I found which was key to getting the cluster to actually operate, was jumpering the two pins on a bi-pin plug along the bottom side. 12 volts was running to one pin, and the other pin was wired indirectly to other points on the board which were also supposed to be receiving power. My logical conclusion? Jumper the pin. I first jumpered it with a 1 ohm 1/4" resistor... just to act as protection and carry the load in case this was not the correct solution. Cluster fired up. I don't know what plugged into this originally- if anyone knows please speak up otehrwise I'm going back to the yard to check the wiring.

 

While I had the cluster apart, I went through and tested all of the capcitors with an ESR meter. Everything looked good.

 

There was another gentleman on the board here who posted on the subject of his intermittent digital speedometer some while ago, and upon a visual inpection, blamed the capacitors, which appeared to be "leaking out their guts" and leaving brown stuff all over the board. Well, this was deinitely NOT the case in his instance, as this brown stuff is common in 80s Japanese electronics and is just a glue used to keep components from moving on the board. Small capacitors do not 'vent' through the top in this way either, their mode of failure is usually seals along the bottom failing, which causes a corrosive solution to leak out and eat through traces on the circuit board. You can always smell this type of failure, because that solution smells like dead fish. Easy mistake to make though, particularly if you are familiar with bulbing/leaking capacitors on PC motherboards!

 

So, what am I trying to say? If you're trying to repair a cluster, don't mind this brown glue around various components on the board. Mine tested OK so I opted to leave them in.

 

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After reflowing every solder joint on the board, the gauges went through a self-test just fine!

 

I've detailed this in a video... looks like embedding does not work here, so you'll just have to click the link to YouTube:

 

I will post follow ups as I make progress on the conversion.

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