Hi folks.

So now that the temperatures have reached the -s, my heater decides to give up.

Ran the diagnostics and it gave an error code indicating the solar sensor. So I replaced this VERY expensive item. Nope, wasn't that.

Replaced the pollen filter becaus it needed changing while I was in there.

The blower fan is working fine, as is the deflector. However, I noticed the air coming from the internal matrix was cold. Unfortunately I couldn't reach it to see if the water was hot. I assume not.

So my question is:

Is there a valve (must be) that controls the water flow to this matrix and if so, where is it hiding?

 

Check the coolant level, both in the overflow container and in the radiator itself (when cold).

 

@Dingus Can you return the solar sensor and get your money back? I try to let people know that when you scan for trouble codes while the vehicle is parked inside those solar sensor codes will always show up. It doesn't mean there is an issue with the sensor itself. If you park the car outside in a driveway or parking lot those codes won't show up. If they do, you can clear them and do another scan. I bet on the second scan they will have cleared completely.

 

Unfortunately thinking the sensor was bust I didn’t use care removing it.

Since I started this post:
Checked the function of the pollen filter, which was fine.
I’ve found the temperature at the thermostat was at running temp, at the outlet from the engine to the matrix was only 52° and at the internal matrix it was only 11°.
I flushed the matrix but it was clear and ran well.
I removed the thermostat and tested it in boiling water and using a heat gun. It never opened.
Now waiting on a new one being delivered.

will update when possible

 

The water was actively boiling and it never opened? Thats a first. No heat is 90% low on coolant on the engine side. Any pinhole leak will prevent the system from refilling itself during cool down. Also at those low temps the two block coolant heaters should be active trying to heat the coolant. They are on the back right side head B1 pointed at firewall. There are two large white wires connected to them.

 

Have you since installed the new thermostat and did it resolve your issue ?


2007 Lexus IS 350 thermostat replacement;


Heater hose location on passenger side firewall near battery (Inlet heater hose referenced by Yellow arrow / Outlet heater hose referenced by Black arrow);



Thermostat housing


Thermostat shown inside housing (referenced by Yellow arrow)