Heater fan control
 

I have an ES300 (97) and sometimes the fan will not run unless I hold the increase button down then it goes to high until I let off the button.
Once in awhile it stays high for 5 seconds then slowly blinks back down to low.
Sometimes it works right away when it's ice cold and sometimes not.
I see in the troubleshooting guide there is an input from the coolant temp sensor into the ECM and a tap from there to the AC controller.
I am guessing it is not supposed to go to high until a certain temp is reached.
Is there a latching relay or a connection that is intermittent?
If anyone knows for sure if there is a temp limiter on the fan speed control, please post.
Thanks,

PS this is a repeat of my post in a similar IS300 thread

On some of the earlier Toyota/Lexus models, '92 for certain, a relay was used for maximum blower speed to bypass the solid state control transistor as even at saturation it would still drop enough voltage to have an adverse affect on blower speed.

Sounds as if the relay still works but the transistor does not or is intermittent for some reason.