hi there i have a 85 gmc 1/2ton 4x4 350 and i find my truck doesn't seem to be warming up to good. i live were it is really cold -25and up, and i find my temp gauge won't go past 160. what could be causing this,new thermostat 195, cardboard in front of the rad, anti-freeze is full. someone please help me figure this out/ about one week ago it would go to 190 and it was the same weather and everthing.:mad:just put the thermostat in today. i forgot to mentiion it use to have a/c but everything was strip out but the heater box

Test the thermostat in a pan of water on the kitchen range using a candy thermometer to monitor the temp.

it is the second thermost that i have put in it in two days.the frigine thing just won't heat up proper

Test the temp gauge by putting the sending unit in a pan of boiling water.

With respect to cardboard in front of the radiator I just KNOW that what you did was take a piece of cardboard and cut a circle out of the center of it so that you didn't unbalance your fan, right? Thats hard on the waterpump if you do it any other way. :)

Having lived and mechanic'd in Minnesota for 25 years or so I am aware of the mischief an improperly applied piece of cardboard can visit upon the cooling system.

I am with Shurkey. Test the guage. You didn't say that you aren't getting the normally hot air out of your heater so I'll assume that the water is hot but the indicator is not. :)