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Has anyone added a digital tach in the clock opening?

You suck for posting that up.:D I though I had a cool inexpensive way to add a tach. Now I may need to spend a crap load of money.:doah:
 
I have one like that from a mid seventies 2 ton. My dumb brain never wondered about a newer version for my Jimmy. :doah:
 
Has anyone tried getting a small GM fuel gauge and installing it in the blank hole on the left lower section of the cluster and installing a GM tach in the original fuel gauge hole and then using a dash circuit inlay for a vehicle with a tach? Would this work? I would think the inlay would correct for the gauge location if you got the right one? Inquiring minds want to know.
 
82355 said:
You can just repin the connector.

Martin
Click to expand...
I'm looking for a easy way to not burn up any gauges and was wondering if I used the printed circuit from the truck that had a tach instead of the truck like mine that did not have a tach,would I be able to just remove the large gas gauge and install a small gas gauge in the correct spot and install a new tach where the gas gauge was and have it work. I would think someone has tried this already? Anybody???? Charlie
 
Many years ago, I put a small analog tach in the empty hole. The hardest part was adding clear plastic over the opening and making it look like it was part of the same piece covering all the other gauges. Eventually I ended up with a late K5 bezel, which had the full clear piece and the DIN radio opening. Can't find any pics with the little tach, though. I found that the tiny tach was hard to read down there because of the angle. To see the needle lined up with a tick mark required kind of leaning down. The digital one would probably solve that.

So I ended up using the stock (giant) fuel gauge motor and putting it on a small gauge backplane, which sits in the "clock" hole (I must have gotten this from a parts cluster). The visibility is OK there for fuel and it looks stock. I took the guts from the tiny tach and made my own tach scale for it and mounted it on the old giant fuel backplane. By far the hardest part about this was mounting a stock needle (the aftermarket tach has no "stem", the needle is behind the front plate) and adding weight to the backside to "balance" it. Otherwise it reads low all the way to the 12-o-clock position, then starts reading high after that. I used a function generator on a bench to calibrate it.

tach.JPG

Above is the earlier scale I drew. Later I switched the tach to "V6" mode and drew the scale accordingly so it was a 6k tach instead of an 8k one. Because who am I kidding with my old school SBC?
 
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82355 said:
https://ck5.com/forums/threads/wiring-up-a-1979-cluster-in-a-1990-k5.293281/

Martin
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What you did was not exactly what I was talking about. You used a 1979 cluster in a 1990 vehicle. I have a 1988 V10 suburban with no tachometer and a large gas gauge in the right position next to the speedo. If I buy the the small gas gauge and a tach and the tach wiring overlay for the cluster (all for a 1988 cluster) and put the tach in the old gas gauge position and the new small gas gauge in the empty position (where it would go if it was a tach cluster) would the wires be in the right position in the plug for all to work. Hard to believe that GM would move wires around in the plug when they could move them in the overlay.
 
ballencd said:
What you did was not exactly what I was talking about. You used a 1979 cluster in a 1990 vehicle. I have a 1988 V10 suburban with no tachometer and a large gas gauge in the right position next to the speedo. If I buy the the small gas gauge and a tach and the tach wiring overlay for the cluster (all for a 1988 cluster) and put the tach in the old gas gauge position and the new small gas gauge in the empty position (where it would go if it was a tach cluster) would the wires be in the right position in the plug for all to work. Hard to believe that GM would move wires around in the plug when they could move them in the overlay.
Click to expand...

I think I understand your question, the issue is that a clock is a constant 12V and the tach is ignition only, plus it's three wires. Clock is two. That would force a re-pin plus addition of a wire at the connector.

Not sure when the clock ended, but at some point GM simply quit making the flex circuit with provisions for it. Just a hole in the flex circuit. Arguable statement ahead, but GM quit installing the tach's in C/K's around 1981. Wiring not really not an issue for GM once that happened.

Back when they were easier to find, Dad took a late 70's camaro tach, removed the fuel gauge motor from the truck fuel gauge, glued the camaro tach gauge face to the stock truck large fuel gauge, and riveted the tach driver to that.

The way the clusters are designed, couldn't tell it wasn't factory, except that the font was incorrect. The above-linked combo tach/fuel gauge is nice, except you lose the light positions underneath.
 
The clock was an option, never standard.

I believe 1982 was actually the last year for the optional tachometer.

Martin
 
Clock option had to end when all the radios went digital, no? I assume that happened around '88?
 
dyeager535 said:
Clock option had to end when all the radios went digital, no? I assume that happened around '88?
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At this point my question would be......Why do you need different flex circuit boards if the wiring is different in the plug? My thoughts are that the flex circuit board routes the signal to the correct place for the gauges and if one used a tach flex circuit board then the tach could be put where it was factory option and the small gas gauge could be put where the factory gas gauge was and it should work.....no re-pining. At some point GM had a standard and I would think it was in the plug. Just my thoughts. I have been around the block but just not the CK5 block.
 
As I recall the tach was not part of the flex circuit. It was a direct 3 wire connector. Where the factory fuel gauge contacts the flex circuit, is just a large cutout in the factory tach clusters. The housing is different as well as the flex circuit. No idea why they had to do that. So forget what I said before, I don't think they were ever run through the instrument panel (IP) connector.

Most likely reason GM discontinued the tachs, it probably saved them a fair bit of parts (money) for as rare as tachs were. At that time GM was getting away from tachs, so it made sense in multiple ways, at least to the money-counters. Since all gauges/clusters don't require the same wiring, they had to change the flex circuit AND pinout to accommodate all the different power/signal inputs for a specific gauge/location.

There were a LOT of cluster variations in the early 80's...idiot lights only, gauges/no tach, gauges/with tach/small fuel, clock (optional with gauges AND idiot lights?), diesel (80PSI oil pressure gauge, no choke light, some additional warning lights), gas (choke light), 4WD indicator light, and probably some other variants I'm missing.

Only 16(?) IP terminals to do it all in. IIRC, even the early 4WD indicator lights didn't run through the IP connector.

Heck, here is an '81-89 cluster housing (no idea for sure which of those years I got it from, the gauges are mismatched) and even it's not cast for the clock:
old%20cluster%20colby_1.png


The '90-91 clusters are vastly simplified, if not even earlier due to EFI introduction in '87. No provisions for a tach, no provisions for clocks or small fuel gauge. All power and all grounds were on the same circuit because all power is switched ignition at that point. Saved a fair number of terminals on the IP connector.
 
The tach wiring is separate from the printed circuit.

The printed circuits have lots of variables from year to year.

Martin
 
My 1988 V10 Suburban has a factory clock, but 1988 still used a two knob radio.

I'll have to look at some 1989-1991 V series trucks.

Martin
 
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