Temp gauge isnt working, change the sensor. Didn't do the trick, think it's wiring or gauge. How to go about that? I got and external gauge but it's only reading like 150 at the highest. Is that normal?

 

If 150 is all you're getting, I'd say you need a new thermostat. The gauge in the truck isn't very accurate. It basically says yes, it's at operation temperature, it's hot, or it's cold. 150 will not move it very much. It needs to be in the 185-195 range for it to move to its normal location.

Now, when replacing the thermostat, I have found it best to buy a new thermostat housing too, because every one I have changed leaked when I just replaced the t-stat. Those housings are very thin and must warp a little when removed. I consider a new housing cheap insurance for having to not take it apart again.

 

i was kinda thinking that, but there's hot air coming out of the heater so I leaned away from that. Could that still mean the thermostat

 

How hot is hot? Where is the external gauge mounted? 150 is cold. How hot do the heater hoses get?