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Geologist

92 GP Speedometer error correction

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Geologist

Hello everyone,

I removed the instrument cluster from my 1992 GP and would like to bypass the calibration resistor for the speedometer.

I have read a few posts by RobertISaar where he  describes the resistor in question and states, "focus on the white blocks. you'll notice a large section and a small section on them. the large section on the 89-93 UB3 controls the gain for the speedo/tach needle. i remove the connections the PCB has to the resistor on those two pins and calibrate it using a 25-turn 500K potentiometer"

OK, I have located the DIPP for the speedometer (see pic below) and have the appropriate potentiometer.

20191007_213528.thumb.jpg.b940552168b62c0f0318679b1400357b.jpg

I also posses more than adequate soldering skills (was my bread and butter for a few years).
 
So my question is, am I reading which two pins to cut and solder the pot in place of. The blue arrows in the picture below is my best guess.

20191007_213528-B.thumb.jpg.809b01ff31fa08f6b09ad0304f5b02c4.jpg

Seems like Saar may be busy, so if anyone can affirm this is the right place to do the surgery it would be much appreciated before I do the cutting.

 

Thanks for your help.

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Geologist

Update

It may be a moot point now.

I got impatient and went ahead and deleted the resistor I thought it was and replaced it with the potentiometer. I set it to 20k Ohms higher than the original and now the speedometer just stays at zero.

Guess it was not the right resistor to replace.

Please advise if you know where I went wrong.

Thanks again.

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Geologist
On 10/15/2019 at 6:45 PM, negativeMatt said:

Robert is easier to reach on facebook these days...just FYI
 

Thanks for the info.

I realize most people are these days, yet I have no facebook account.

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Geologist

I ended up getting another cluster from ebay.
It had some problems but I was able to make one working unit out of the two.
The speedometer still needed calibration so I made sure to do the mod right this time and the speedometer is now very accurate.
A special thanks to RobertlSaar for contacting me when I reached out, very helpful!
For clarity, in my original post the picture showed the wrong resistor to replace (hence my need for a new cluster).
This pic is the resistor you need to replace if you have the know how and confidence.

20191007_213528-C.thumb.jpg.bcd3b15a8eaf3f75cb476616888acb59.jpg

Now, can anyone tell my why the Low Fuel light is always on in my new cluster (it is the only problem with the new cluster I haven't been able to fix).

Thanks again to everyone who has helped.

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Geologist

After my last post I did a search and found the following on the forum:

On 9/19/2017 at 11:35 PM, RobertISaar said:

from the GP clusters I've had in-hand.... all 89-90 UB3 clusters(not the half-digitals, though they wouldn't surprise me) will have the speedo and tach go nuts, it's when, not if. I imagine most have by now.

SOME 91-93 clusters have the speedo and tach get out of whack. not all, for whatever reason(I'm not sure if it's a build date related issue or not).

all will have the check gauges and low fuel light issue, at least once, eventually. GM's choice to use whatever the hell lacquer-like conformal coating on  the last ~4" or so of  the board seems to cause issues. 

Taking his advice I re-flowed all of the solder joints on the board and the Low Fuel light now works as intended.

Thanks again to RobertlSaar!

image.png

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negativeMatt
After my last post I did a search and found the following on the forum:
Taking his advice I re-flowed all of the solder joints on the board and the Low Fuel light now works as intended.
Thanks again to RobertlSaar!
image.png.317bec02998e9c99e5631b80cf89dc6e.png
Did you have any other issues? Weird tach or speedo?

Sent from my SM-G935F using Tapatalk

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