I have a 95 Silverado 1500, 5.7. I replaced the sending unit twice, thinking the first one was bad. With the sending unit out of the vehicle and plugged in, it reads 100 deg. place the sending unit against the block and it pegs out at 260. Could someone please help me figure out what the problem is?

 

Make sure you have the correct sending unit for your engine.

 

I made sure that I got the correct sending unit the 2nd time. same problem.

 

Try installing it with thread sealant.

 

I used Teflon tape. should I use something else?

 

You didn't post that you installed it, but held it against the block. Teflon is fine. Do you have an ohmeter? If so, check the pins none installed for what resistance it has, then re-install it. It shouldn't change, but either it is, and that is causing your issue, or you need to look at the gauge. As you pointed out this is the correct sending unit, these are matched to the gauge.

 

I measured it uninstalled and it read 1.86k. I installed it and it read 1.36k

 

At this point, can you see if you have a chaffed wire from the sending unit back to dash?

 

I followed the wire back to the firewall and it appear to be good

 

Does the gauge automatically read high when you turn the ignition switch to on?