Expert: Roland Finston - 7/21/2011

Question
2000 town & country, 3,8 engine..
new radiator,fans, new thermostat, radiator cap, water pump, temperature sensor on a side of thermostat housing, new - original A/C relay (under the L/head lite...)
overheating in a 10 min, with "A/C" button "ON", just on a "P",
not overheating when driving..
when is overheating, A/C stop working, fan star blowing HOT air.
No CODES...
mention on a brain box problem, hydrocarbon build up.. not sure..
Please advice..

Answer
Hi Dave,
A few questions:
What do you mean by "just on a "P". Did you mean while parked?
Are you getting low speed fan and then as the temp gauge rises is it shifting to high speed action?
What are the symptoms of overheating? Temp gauge goes how high? Loss of coolant from filler bottle? Or what other than AC cutting out?
What is the recent history of the AC system? Refrigerant refill anytime recent?
What is the ambient temp when this occurs, and how about does it do it in cooler situations?
The relay you mentioned as being under the l/headlite is actually the radiator fan relay. The AC compressor clutch relay is in the power box in the engine compartment.
Of course it is the case that if the ambient temp is in the 90's and you aren't moving, that it puts a real demand on the system to dissipate the heat from the engine and from the A/C. Do you have to operate in park like you say is the problem, or did you just experiment to see whether it could do that successfully?
Sorry to ask so many questions but there are a lot of details in an issue like you have.
Roland