Heater, Cooler

What temp should the max heater output
be? My car, an ’06 Magnum 3.5L,
is slow to heat. The dealer has replaced
thermostat 3x, flushed entire system, no
improvement. Chrysler tech services recommended
replacement of radiator, heater
core, oil cooler and reserve tank—done and
still no improvement. Car takes 20 minutes
from cold start to reach ³ reading on temp.
gauge at a –5° Celsius outdoor temperature.
Five minutes later temperature was slightly
above 3° and I then turned heater fan on.
Temperature immediately dropped to 3°
of gauge and heater output temp. at dash
was 115° Fahrenheit. At max. temp. setting
& max. heater fan, heater output temp.
dropped to 102°F in 5 minutes. Car will not
maintain temperature while idling. While
driving at highway speed, it will reach near
normal temp on gauge.

First you need to determine if the problem
is actually cooling system related or heater
related. Use an IR temp gun on upper rad
hose or on coolant itself with cap removed
(remove when cold, then warm up). Should
be approx 195°F or greater. Gauges are now
programmed to be stable (no movement) if
temp is safe—so there should be virtually
zero needle movement once warmed up.
Have the dealer check for codes—“engine
coolant temp too low,” etc.
If not hot enough, coolant is somehow
bypassing the thermostat. Period.
If OK, I’d try running tap water though the
heater core to confirm that flow is normal
(garden hose, etc., flush in reverse), even
though it was supposedly changed.
On many new cars heater core is highest
point in system, which can be tricky to bleed.
Trapped air will cause very poor heat output.
Most new cars use a blend-air system:
The heater core is always at max temp
(195°F). Possible bad/sticky blend-air door,
servo motor, etc.
The last two suggestions are actually my 1 and #2 hunches.