Chrysler Repair: 00 Chrysler Cirrus: insuffecient heat, chrysler cirrus, 2000 chrysler cirrus

Question
QUESTION: 2000 Chrysler Cirrus
Heater started running cold.
Replaced thermostat, no improvement.
Replaced coolant temp sensor, no improvement.
Interestingly, when I disconnect the radiator fans, the temp gauge increased to 50% from 25-40% and the heater blew hot.
It appears that the fans are coming on too soon and keeping the temp down.
I have checked both fan relays and they are within specs.
I have run out of ideas.
Any on your end?
Thanks.


ANSWER: Hi Roger,
The temp sensor and thermostat are the key factors.
Might it be air in the cooling system?
Which engine do you have?
What are the outside temps when you are using the heater?
Might the blend-air door in the ac/heater housing be flaky?
Are both hoses that go through the firewall to the heater about equally warm?
Those are the possibilities I can think of.
Roland

---------- FOLLOW-UP ----------

QUESTION: Thanks Roland,
This is the V6 which means to access the heater hoses at the firewall, I need to remove the upper intake manifold.
I may do that as a last resort to flush out the core, but since I can get the heater to work if I disable the radiator fans, the core is getting hot water.
I am able to touch them at another point and they feel equally warm.
These symptoms are worse as the outside temps drop.
I have removed the bezel/radio earlier and was able to see the temp control cable attached and working.
I cant seem to get the dash temp gauge up to 50% without disabling the radiator fans...that would seem to point to the thermostat, but I have replaced it. With radiator fans disabled heater works great.
The fans kick on when the dash temp gauge is about 25%.
The heater will have about 10 seconds of hot air then you can feel it go cool.
I'm about stumped.
Thanks.

Answer
Was the opening temp of the new thermostat around 190F or higher?
Is the coolant temp senor reading about 1k across the contacts or less when the system is fully warmed up?
Those values should be verified.
Water pump drive belt might be slipping, or pump not working well do to an impeller problem.