2003 blazer, 2 door
I put in a new fuel pump, and then noticed my temperature gauge is messed up as shown in the pictures after the truck was started and then turned off. Is this an electrical issue, maybe the cluster or is this the coolant temp sensor going bad?

 

Did you disconnect your battery when changing your pump?

It's possible that your battery arc'ed at some point and caused it to jump off track.

Something similar happened to me. Just take the dash bezel off, remove your cluster, and manually (and carefully!) move it back.
As soon as you turn it on, it will reset itself back to normal. Hopefully.

 

Yeah I did disconnect the battery before I rewired the new harness for the new pump. Now that I'm thinking about it, I have noticed a couple times since I've had the blazer that my dash has flickered off and on while I've been driving so I think I just need to pull it out and see like you said. It will be a first time for me taking a cluster out.

 

Also be sure to double check your battery connections... Make sure there is no corrosion.
And remember.... Remove the negative first, then the positive... opposite to put them on.
Removing the positive first can cause funky electrical glitches.

 

Never heard of it causing glitches, the amps don't care which you take off first. You should pull the negative first, so that if the wrench slips, you don't short out your battery. If the negative is attached, and you accidentally make contact from the positive to any metal object, dead short on the battery. If the negative is off, there's not a complete circuit, so no spark

 

Agreed

 

As it has been mentioned before -
Yes in the old school Pre.computer days all you had to worry about was dead shorting the battery and having it blow up in your face.
With the computer controlled vehicles by hooking the POS up first as funny as it may sound even tho the NEG on the battery isn't hooked up yet it preloads the system with voltage so when the NEG is hooked up there is no voltage surge thu out the system.
When the NEG is hooked up first the voltage surges thu out the system in a hard wave.
Same theory when unhooking battery if the POS is unhooked first as you loosen the bolt or clamp and remove the lead the voltage arcs as its unhooked throwing waves of voltage thu out the system

 

Odat, I've never once heard of that. Do you have any sources or articles discussing it? I have a degree in electronics, and that was never even mentioned lol