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Hello, Recently since it has started getting cold and I am needing to use my heater, I am realizing that my heat does not get hot like it should. My temp gauge will be in the middle where is should be for awhile but still my heat blows cold air. After running for while, when I kinda rev the truck up a couple times then the air gets hot for a little bit but sometimes it stays hot and sometime switches back to cold. I am not really sure where to start looking but and help would be great. Thanks. Also I am not sure if it matters but in the summer i realized that my air conditioner did not blow extremely cold air. I tried charging it with r134a but it was full so it didn't do much good. Anyways I didn't know if these problems were connected or not. So please get back with me asap. Thanks
IF you have a crewcab truck then you have a valve in the heater line just above the passenger side valve cover with a small gray vacuum line going to it. Check that valve for proper operation. With the AC controls in the off or AC Max position the valve should close. The easiest way I've found to check it is to simply turn the key to the run position, wait for the vacuum pump to shut off and pull the vacuum line. You should see the valve move. It's also very easy to move by hand.
This is the easiest thing to check first. You could have airbox problems under the dash or a vacuum pump not working the airbox correctly but it doesn't sound like that.
FYI--the dash gauge is totally worthless. It only indicates cold/normal/hot, but sounds like your truck is warming up "OK" and that the heater is malfunctioning. Also, if your coolant is abnormally low you could have a heat problem. CORRECT level is 1/2" below the minimum level on the degas bottle when COLD.