musicman67

Apologies if this has been discussed elsewhere...I could not find a thread.

2004 ES 330, 45k Miles

When I set my system to a heat temperature range, I only get heat intermittently. Sometimes it still blows cold air. I have checked the driver and passenger damper servo motors, both are working fine. I have read there is a 3rd, but I cannot find it...maybe that is only other Lexus models. Doesn't matter if I run it in Dual mode or not. When I set the system to HOT, I get extremely hot air. I assume that setting has a separate ceramic heater though. I have also checked coolant levels. They are full and I took time to bleed the system thinking there might be air trapped. Really did not get much of anything out of it and it made no change. It seems to be that when the ambient temperature is around 75 degrees or above, I cannot get any heat to blow out. This is even when I am not in AUTO mode. When it is a little cooler out, I seem to get hot air out of the vents. Temp gauge in the dash sits right at or just under the 4th hash mark when vehicle is wamred up.

Is it possible that the ambient temperature sensor affects the air heating system even when not in AUTO mode?
Would a coolant flush be an option if there is air trapped deep in the system?
Thermostat replacement possibly needed?

Any help or info would be much appreciated.

Thanks,

Joey

Oro

By "intermittently," You mean sometimes, given the exact situation, it does one thing, and sometimes another?

I am not 100% sure there is a problem here - in warm weather, and 75F certainly qualifies, I cannot get any heat unless I commit it manually to full hot. I don't view this as unusual. Maybe I am not understanding your situation, though. I do know that it is really helpful when bleeding the coolant to get the nose of the car uphill - parked that way, or on ramps/jacks. I am not looking at my dash this minute so I can't say where the 4th hashmark is, but at normal operating temp, the needle should be slightly below level, like at 3/8ths of the range if that helps.

musicman67

If the heat/air systems in these cars are designed to operate this way then that is fine. I just found it a little odd and wanted to make sure nothing was operating incorrectly. I didn't bother to get the jackstands out when I bled the system, but will do that next time to give myself a better chance of getting any air out. Thanks again.

djw1960

I have a similar situation. I changed out the servo on the drivers side and checked the one behind the glove box and they are both working correctly. However, the car only gives us full cold or full hot, nothing in between. Not sure what the issue is.