I have a 1999 LX470 - 160k miles - original owner- garaged - completely stock - well taken care of - no modifications of any kind.
I'm looking for help with the function of the climate control/heater. Here is the problem:
In cold weather, when the car is started dead cold, the climate control immediately turns the blower fan on full blast, as if it's trying to heat the cabin, but with no warm coolant in the heater core. The climate control unit is on auto temp and auto recirculation.
Eventually, when the engine warms the coolant and heat gets to the heater core, the system will heat the cabin and function normally, floating the temp at the prescribed level. So, in essence, the system works perfectly when the engine is warm, except at the initial start when the engine is cold.
Here is what I determined and checked:
It appears the system can't tell there is no heat in the engine/heater core and "thinks" it is warm and immediately starts blowing (cold ambient) air at full blast at first start. I checked the operation of the air mix motor/servo and it appears to be functioning properly. The blower fan is functioning properly. I also used the button combination on the climate control unit to look for errors and the only error showing is "21", which is normal for doing this in a dimly lit garage (sunlight senor). No other codes show.
I also put a laser temp scanner on the hoses going into the heater core and they do register engine temp going in and a lower temp coming out, so that shows there is good coolant flow through the core when the engine does reach temp.
The A/C works perfectly, I checked that operation. And the A/C compressor is not engaged when in heating mode. The engine temp gauge works correctly.
So, what method/device does the climate control system use to determine if there is heat in the engine coolant/heater core? It appears to be blinded to the fact there is no heat in the engine/heater core and acts as if the engine is warmed up. I suspect the device that measures engine/heater core temp may be the problem as the system works perfectly otherwise but appears to be "fooled" that the coolant is warm at first start when it is not.
Any thoughts in what direction to look?
I'm looking for help with the function of the climate control/heater. Here is the problem:
In cold weather, when the car is started dead cold, the climate control immediately turns the blower fan on full blast, as if it's trying to heat the cabin, but with no warm coolant in the heater core. The climate control unit is on auto temp and auto recirculation.
Eventually, when the engine warms the coolant and heat gets to the heater core, the system will heat the cabin and function normally, floating the temp at the prescribed level. So, in essence, the system works perfectly when the engine is warm, except at the initial start when the engine is cold.
Here is what I determined and checked:
It appears the system can't tell there is no heat in the engine/heater core and "thinks" it is warm and immediately starts blowing (cold ambient) air at full blast at first start. I checked the operation of the air mix motor/servo and it appears to be functioning properly. The blower fan is functioning properly. I also used the button combination on the climate control unit to look for errors and the only error showing is "21", which is normal for doing this in a dimly lit garage (sunlight senor). No other codes show.
I also put a laser temp scanner on the hoses going into the heater core and they do register engine temp going in and a lower temp coming out, so that shows there is good coolant flow through the core when the engine does reach temp.
The A/C works perfectly, I checked that operation. And the A/C compressor is not engaged when in heating mode. The engine temp gauge works correctly.
So, what method/device does the climate control system use to determine if there is heat in the engine coolant/heater core? It appears to be blinded to the fact there is no heat in the engine/heater core and acts as if the engine is warmed up. I suspect the device that measures engine/heater core temp may be the problem as the system works perfectly otherwise but appears to be "fooled" that the coolant is warm at first start when it is not.
Any thoughts in what direction to look?