For the life of me I cannot find answers for this dilemma. I can't seem to get the engine temp to middle range on the marker, but yet my heater blows "to me" hot air. Even while sitting in idle for extended amounts of time I cannot get it to "operating" tempature. I would think if my thermostat was stuck open my heater would blow either cold or slightly warm air.
Any help would be greatly appreciated.

I have the 5.4L engine with knn air filter and no cats. If that helps at all.

 

Sounds like a stuck open or broken thermostat.
Have you considered taking it out and looking at it?
You could also boil it to verify operation.
What have you done to diagnose this besides run the heater and look at the gauge?

 

I've flushed and refilled the coolant and checked it for the right ratio. After a few errors on mixing I got it right. Just replaced the thermostat yesterday and it still does it. I've even checked the fan for resistance with my hand while it's hot. And it spins easier when it's cold. So now I know the fan isn't fully engaged all the time. I don't know what else to check now.

 

It may be nothing more than that the sending unit for the gage is bad. Try replacing that and see what happens. My Suburban reads low because I replaced the stepper motors and messed up the needle so it always reads low.

 

What would be considered low? I'll take a picture and post it while the key is on and the engine is cold. And then while the engine is "warmed up".

 

Sounds like it's functioning as designed. Just because the needle doesn't sit in the middle of the gauge doesn't mean anything is wrong. I wouldn't worry about it.

 

So operating normally but still cold? I don't understand it.

 

Is it cold? The normal operating range is huge on these gauges.

 

I believe it is. The grave doesn't get more than a 1/4 way past the absolute bottom. But the heater blows hot air.

 

Here is key out and key in with accessories on. I'm gonna drive around a few minutes and let it idle to warm up and take another picture.

 

If you have a buddy that has a scangauge II that you could put on it, would possibly help narrow the issue. Also, you may can take it by a local parts store and have them use a thermal temp laser to give you water temps at the radiator and the all water hoses. I know they are fairly cheep at Harbor Freight if you have one close by.

 

I'm gonna check it with a scan tool and look for a infrared tool when I get to class. I'll check and record the temps once I do.

 

You could also pick up a Bluetooth OBD II unit and a smartphone app which would likely have the coolant temp as one of the parameters.
I use a Lemur with BlueDriver app but there are lower cost alternatives.

 

I'm attending a technician school. I'll just use the scanners they have in the tool room.

 

This is driving for a bit and letting it idle until the gauge stops moving.