Heat issue

[themixerdoc]

So have not been able to find a solid answer to this issue.
Vehicle is 1998 QX4. Started on Wednesday prior to this heat was fine. So listing the symptoms as I am experiencing them and based on a limited amount of troubleshooting.
Temp gauge rises to normal position. Engine acts normally and system "appears" to warm even down to achieving high enough temps to have torque converter lockup. But as vehicle is driven from cold start climate control system also appears to do everything right. System stays off until engine temps begin to rise. Fan ramps up slowly at first but as temp gauge rises so does fan speed. Issue is air blowing out is "cool" at best.
I have checked both heater hoses and both get rather warm (though as you can imagine none of the hoses is really "hot" with high temps outside of maybe 5F). Upper rad hose warm also. Lower hose pretty much cold. Temp of coolant in rad does not rise above 165 to 170F (digital thermometer in rad neck). The highest temp comes during idle. If I run the engine up to say 1600 to 1700rpm the temps steadily go down dropping to under 160F measured in the rad neck
Upper hose and heater hoses are about the same temps as each other though.
My thoughts (but I am unfamiliar with what appears to be a reverse flow rad). If I have a bad thermostat (stuck open?) why do I not see coolant flowing in radiator. Fluid appears quite "still". Not at all what I am used to.
I have also tried raising and lowering temp setting on HVAC system. Raising does nothing but if I lower it the fan speed does change though I have not noticed an airflow change.
So this is what I am faced with. Any and ALL help (especially quick help MUCH MUCH appreciated

[MisterH]

From your description your engine is not even reaching operating temperature; which is bad not only because your heater won't work but puts your engine in perpetual cold running state. The only cause I know of is a thermostat that is not closing.

[themixerdoc]

Oddly I thought the same thing. I was going to replace the tstat myself but seeing where it is and having my left hand not fully functioning due to a nerve injury to it over the summer while working on my boat I took it to a trusted garage. Their testing said the stat was functioning correctly but the heater core was clogged. They did a complete flush of the core and cooling system. Said when they flushed the core huge amounts of goop came out. This oversight was mostl likely my fault for trying to check the heater hoses with brutally cold hands due to the air temp (even in my garage) being just below 0F. Tech said when they checked inside the shop it was clear the hoses were not equal temp as I had thought. A little puzzled why the core would be so clogged. Tech said the Nissans, Dodge Ram, Chev Blazer and offshoots are noted for this. Knock wood I now have good heat again. Weird thing is day before this happened I was driving it in the cold no issue.

[MisterH]

Good. It was no doubt a cheaper issue for them to fix than replacing the thermostat.