1990 moon gauge issues

[Munch]

Temp gauge reads 260 but reads 200 at the temp switch. Has full tank but reads ¼ and the speedo is of by a lot. Tire size is stock. What's going on. Known issues? Fixes?

 

[DerekTheGreat]

Sounds like that isn't the original cluster if the speedo is off. Unlike the late model '91 and up trucks which have an external DRAC module, the speedo calibration is done within the cluster itself. GM used to sell a kit for aftermarket calibration but I couldn't find any when I did the Moonie to Needle swap on our '88 and '89 trucks but got lucky as the clusters I installed were already set up correctly. The cluster that went in my '89 had the aftermarket kit from GM in it...

Anyway, my fuel gauge didn't read right either, back when it had moonies. Thought I'd have to dicker with sending unit in the tank but after the swap things worked perfectly. Sometimes the stepper motors crap out.