river

I tried turning on heat but it blow cold only.

salimshah

Start with simple things first .. check for coolant level in the radiator (not the overflow) with the engine cold.
Then check if the air mix servo is working as you adjust temp settings from cold to hot. [use search]

Salim

evopat

I am assuming your car is not overheating so you have coolant. If you are running hot please check the level first

There are a few areas that will yield you no heat

Assuming coolest level is ok and when the engine is running you maintain normal operating temperature. If you are not that is your issue. Check the coolest and the thermostat. If that is all good

You could have a mixing valve that will not open
The electronic control that moves the flapper inside the heat box is not working. I have seen the cheap clip on the controller pop and then you either have super cold or super hot no in between
The temp controller itself

Good luck

river

I checked the coolant in radiator it looks fine. After reading on this forum it looks like servo is the issue. When I change the direction of air to front it make strange noise. Also when I say it blow cold air does not mean ac , at temp set to 85 it looks like it is blowing out side air which is pretty cold these days.
I have read there are three servo on rx300 2000, based on my symptoms what you think which one is bad? Also people are repairing them too.

evopat

Ok you may have more than one issue.

More the air direction from front to back works a servo on a flapper to just redirect air not change its temperature. Maybe the other issue has dropped parts into this area and that is what you e hearing hit

On the air temp. Try turning the contols to full cold then full hot listen for the servo movement and the flapper. If you hear funny noises clunking or banging the servo is working and the connection to it is broke. Time to take it apart. If you hear nothing go find the servo its most likely shot. When you get there you can manually activate it to make certain it's not the controller that has gone bad

salimshah

Please do not confuse air mix servo with mode servo. To debug we need to focus on one thing.

Take the system out of auto and then just adjust the temp .. from Hot to Cold to Hot. Look at the servo .

Salim

river

Thanks
by doing from Hot to Cold to Hot.. heat is back.
so it means the servo for mixing is stuck somewhat?

salimshah

Maybe in summer, you would not get the cold air .

With that out if the way, you can now trace the mode servo problem.

Salim

evopat

River, it may not be the servo....

If the heat is back and now it is FULL ON HEAT.... meaning you can not moderate it most likely it is the connection from the servo to the actual door inside the heat/ac box that is lose or broken... When the servo goes back and forth it is moving a rod that is connected to the door... (most heat box work like this). When the door is on one side you get full AC or outside air... on the other you get full heat.... in the middle you get a mix.... If that connection is broken or lose every now and then it will grab it as the rod goes by and pull or push the door to the other side....

The good news.... the fix is usually pennies... the bad news..... you are still pulling the heater box to check the connection...

I would go back and go full hot then full cold manually and listen for clunking or plastic sounds, grinding.. if you have it.... start pulling the box your controller and servo are fine its the connection...

Enjoy

river

Mode or mixer servo?

salimshah

Mix controls temp.

Mode controls which vent the air will come out of.

IN auto mode the mode is typically constantly being changed and you get the disc shuffling noise.



Salim