02 Dash Cluster

[THEFERMANATOR]

Originally Posted by rfletes79

In like Flynn. Thx for the help you guys. Got my overlay yesterday from usspeedo and it looks great!!





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You got an overlay for a gasser instead of a diesel? Does it have the wait to start indicator in the overlay? I looked into a custom overlay for mine, but they were wanting around $160 for a custom overlay. You can tell that's a gasser overlay because it has the 6K rpm tach whereas a diesel only has a 5K rpm tach. I'm not sure how GM calibrated the guages on the gmt-800 99-02 clusters. Earlier clusters used a calibration resistor you could swap out and make the tach correct, but not sure on the 02 how you would do it.

[Chevy1925]

I ordered a gasser overlay a few years ago and sent it back cause everyone was saying the tach would be off. Never tried it so I’m curious how this works out

[rfletes79]

Tach seems to be good, I'll need to verify with my laptop, but so far so good. Just lost my WTS light.

Honestly, I had been looking for a diesel one and thought I found one. But didn't realize it wasn't for a diesel until after I installed it and started it up for the first time.

[2004LB7]

I believe that the tach will correct. You will just have a portion one the high end that will never get used

I thik Ben can reprogram, the cluster or BCM to make it correct if it is not.

[THEFERMANATOR]

The tach will be off. The gas overlay tops out at 6,000, but the diesel tops out at 5,000 at the same exact spot. So it will be off, roughly 20%, so when the engine is turning 1000, the tach will show 1200, or 3000 will show 3600. As to calibrating it, I'm not sure how the 02 cluster calubrated the guages. I haven't played with one to see if they used the old school ceramic resistor block, or if GM stepped up to the logic module for them.

[830king]

Won't the oil pressure gauge be off some then with a gasser overlay?

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[SickLL7Crenshaw]

I didn’t even look close enough to realize Ricks was for a gasser. I can’t remeber but I wanna say there was only like 5 SS Diesel overlays left when I purchased mine from US Speedo back in 2010. He said wasn’t a want for them on those years.

But I do have a buddy that threw a gasser overlay in his 02 and the Tach is off just about like Ferm said. Everything else is accurate though IIRC.

[DAVe3283]

The tachometer and oil pressure would both be off, I think.

If someone knows how to adjust the gauge ranges on the 2002 dash, I'd love to hear it. I'm playing with some 2003+ clusters and would be interested if they are controlled in the same way.

So far, I haven't been able to find out where the scaling is stored, but I have bricked a cluster trying.

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[THEFERMANATOR]

Originally Posted by DAVe3283

The tachometer and oil pressure would both be off, I think.

If someone knows how to adjust the gauge ranges on the 2002 dash, I'd love to hear it. I'm playing with some 2003+ clusters and would be interested if they are controlled in the same way.

So far, I haven't been able to find out where the scaling is stored, but I have bricked a cluster trying.

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I wished I had one here to see how it works. 03+ use steppers which is a push pull type motor setup, but 02 and older used air cores. Air cores work by an armuture being controlled by 2 opposing magentic fields pulling against each other to control position. Voltage was applied to both sides, but only 1 side was directly powered, the other side was powered via the main power, but feed across through a resistor. That crossover resistor was how the guage was calibrated. By changing it, you could change the opposing pull, and recalibrate an air core guage. My only question is does the gmt-800 99-02 air core clusters use calibration resistors like GM had used since the 60's, or did they move the control into the logic module like they did for the 03+ stepper motor design. If it was a gmt-400 cluster, I could easily recalibrate one with some 2 watt resistors, but I don't know if this would work for the gmt-800's.

[Chevy1925]

I have a spare sitting here if either of you wanna dick with it. I’d love to know if I could make a gasser face plate work. Only issue with it is the odometer/gear selector screen died. Everything else worked great (original from my 02).

[melvinalbs]

That looks great.

[rfletes79]

So the tach is off about 150 rpm, seems to be that number all the time..... at idle and at driving speeds. Other then the wts light and tach everything reads as it should.