1989 Base Cluster Fu- ah Swap


Sep 22, 2023
Woodbridge, VA
Vehicle Details
1989 Thunderbird Base N/A V6
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Original thread: 1989 Base Cluster Fu- ah Swap | TCCoA Forums (https://www.tccoa.com/threads/1989-base-cluster-fu-ah-swap.189491/#post-2053595)

I'll repost just the highlights here.

After 30 years of looking at my lame 3 gauge instrument cluster, it's time to upgrade. I obtained a sport cluster from a '93 Cougar, and the '89 and '93 EVTMs.

The '93 book has a very nice wiring chart, much more handy than the schematics.
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The '89 book has no such chart, so I did some copy/pasting on the '93 scan to depict the '89 wiring. This made it so much easier to switch the wiring around.
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Notice the red text. My car has no tach, therefore no wire for it. The number 1 slot in that connector is empty, so I'll insert the tach wire there when it's added.

Since this is my only car I can't have it undriveable for very long. So just in case something goes wrong with the rewiring I have to be able to swap back to the original cluster while I figure out the problem. I decided to make an adapter harness, just like you would use for an after market radio. I picked up an extra cluster from an '89 SC. It was pretty beat up and missing the speedo, so it was cheap.
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I cut the harness connector sockets from the back of the SC cluster. Then I made new circuit traces with 1/8" copper foil tape.
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Copper tape https://www.amazon.com/dp/B01L0BTAX...olid=2EEWEMBS87FGW&psc=1&ref_=lv_ov_lig_dp_it

I tacked down the wires with super glue, to prevent the copper tape from being pulled up if the wires get tugged on. It also made soldering easier.
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Then I soldered all the connections. Some wires had to be doubled up on one trace, and even triple on one.
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Now it's test time, glad I studied! I removed the old cluster.
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Plugged in my custom harness adapters.
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And hooked up the new cluster.
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Tach and oil don't work as they are not wired to anything yet, I assume that's why the "Check Gauges" light is on. Everything else seems to work though.

The gauge lighting also works.
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Even the speedo and turn signals work, which I verified with a trip around the block. It was cool to drive with the new cluster, almost like a different car (with the same squeaks and rattles though). But I didn't want to go too far with a busted odometer gear, so I'll replace that tonight. And reset the numbers to match the old one while I'm in there.
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I got the new odo gears in, no need to cover it as it's well documented. I also reset the numbers to match my old odo, also documented but the picture links are dead on that thread. I looked at it for a while, trying to figure out how it goes together, and I noticed that one end of the axle pin for the number wheels is retained by what looks like a tang nut. The end of the pin protrudes past the nut, so a regular screw driver won't work. I don't have the appropriate tool but I managed to get it started with a pair of pointy hook-nosed tweezers. A few turns got the nut clear of the pin so I could finish with a screw driver.

Here's the nut. It got nicked a bit by the tweezers but no real harm done.
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Removing the nut frees the axle pin to wiggle a bit in the hole, and allowed it to be pulled away from the wheels just enough to turn them one at a time to reset them. So the "new" 75k odo now matches my 142k original.
Last edited:
Hmm, pictures show in the preview but not after posting. I'll have to repost them individually.
Yeah, when you C/P posts with images, it just embeds the images while still pointing them to their URLs on the other site.
Hmm that's odd I didnt have that problem when I was copying my thread over, the images are indeed proxys o the old site but they displayed without Xs like that
When I was copying things over, it was hit or miss whether the pictures would show up or not. Anything that didn’t show, I just edited the post and uploaded them manually.

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