Hello Im a New Member, and in the past ive'd visited the site and its great and all it's members.
Wich got me to Sign up, so here i go...

92' LS400. Its overheating, My coolant level is ok(no leaks) but when i turn my A/C on its starts to over heat and the Tempature Gauge goes up and up.

When I turn my A/C off its stays UP, Also even when i DONT turn my A/C on, it still does it, BUT it takes Longer to heat up!!

**BUT!! i notice that my 2 Front Fans Arent working. I tested the Fan motors and they both work!**

Someone told me that chances are it could be my "Coolant Tempature Switch"
or my " Coolant Tempature Sensor" so wich is it? and what's the Difference?

And if so... [Where is it Located?] maybe its not sending the signal to the computer telling the FANS to Cut ON and cool it Down.

I dont know? Someone Please Help!!!

 

coolant temp sensor is for the computer,the switch operates one of the fans, u also have relays as well

 

Welcome - on my 95 there is an electrical switch or connection that plugs into the fan. This connection is on the bottom driver's side just behind radiator. When I had my last TB service the tech did not plug it in and the fans ran continuously. Hope this helps you.

 

Definately check the fan relays, Fans, Etc.
Make sure your Water pump is working.
These cars dont really have radiator caps within my knowledge.
Make sure there is enough coolant in there.

Its most likely your fans arent running...

 

Our cars do have a pressurized radiator cap as the coolant overflow is "pressurized", which means the hold plastic container is under pressure when the engine is running, so if you have cracks in the coolant resv, you will not be able to hold coolant in your system. The cap is rated for 13psi.

Like he, and Steve mentioned, check that the fans are turning on. Also it wouldn't hurt to pressure check the system. That being said, if you have a full functional system, and it only heats up when the AC is on, I would imagine your fans aren't turning on in order to keep airflow moving over the radiator and condenser. One quick test, get a big floor fan and set it in front the car when idling with AC on, if it maintains the temp, it's simply an airflow problem. Also, try turning your AC on only on the freeway where you are maintaining 25+mph, where condenser fans will shut off. Your car will only run hot when it's not getting enough airflow across the radiator, or there is something wrong with the cooling system in general. The reason why I say that is because cooling fans typically impeed airflow while driving down the road, so it will actually shut off while driving, but when you slow back down, it turns back on to maintain constant airflow across the radiator/condenser.

 

Hey thanks a lot Guys!!! your opinions helped a lot. it was a couple of things and ALL of you were right!! ; It was a couple of relay's and it made my fans work; it was also my Coolant tempature sensor; and i also took my car in the highway and tested it out. Thanks EVERYONE!! u guys are Genious.