Problem with Autometer temp gauge. Bad gauge?

i put an sos pod and a boost/vac and electric water temp gauge in my car a few weeks ago.

only problem is that the temp gauge instantly pegged max temp when it got power. then it would start at the initial sweep and max out within about 30 seconds of the car running.

so i called autometer and they sent me a new sending unit. i installed it today. car ran for approximately 1 minute with it sitting at 100 degree's. then it began sweeping towards max temp. about 2 minutes later or less it was pegged. stock gauge shows no register yet.

does this seem like a bad gauge itself? the ground is obviously good since there is no issues with that.

im using add-a-fuse's. power for the gauge sending wire is seperate from the lumination power. using fuse #20 or 35 for power, i forget, but can check if it matters?

wire is not bare in any spots, have any bad connections, or touching anything else on the back of the gauge posts. any suggestions what is wrong here?

yeah i probably can. dont really feel like pulling the damn thing off to send it in though honestly.

someone said if i had a bad ground, it would do this. i dont see how i have a bad ground though, it is tied in with the other wire grounds i might try and isolate the ground for the sending unit also and see if its fixed. otherwise i dont know.

its in the crossover tube.

how would i wire a ground up to the sending unit housing? sorry, im completely missing that. as i wouldnt wire it from the stem i doubt since the power wire is there? electric is not my strong point in cars.

thanks for the help though. i will give this second ground wire a shot.