Could a bad thermistor be the cause of this heating problem?? I don't know exactly it's function...maybe someone can elaborate--is this is the cause?

 

I am not sure the exact specifics on mixing the heat and cold in our systems, but I DO know that the thermistor controls the FAN SPEED only. The thermistor is a fancy name for "temperature-controlled resistor".

In automobile blower systems, the thermistor allows only a certain amount of voltage to get to the fan motor. Example:

HI speed----12 volts to the motor. Thermistor BYPASSED.

MED HIGH SPEED---9 volts to the motor because the thermistor absorbs 3 volts.

Low-Medium Speed---6 volts passed tgo motor, and 6 volts absorbed by the thermistor.

Low speed-----3 volts passed to fan motor, and 9 volts absorbed by the thermistor.

So as you can see, the thermistor absorbs a lot of voltage in the slow/low speed positions. These slow speeds burn out the thermistor over time.
As a section burns out, usually there is no fan operation in that mode.

Many therrmistors are mounted just above the fan motors (Toyotas) but many are in the fan switch. If you have a car that has a fan that only runs on slow or fast, perhaps your fan switch is bad. Just measure the voltage at the fan using a DVOM. The switch should vary the voltage at the motor depending on fan switch position.

Good Luck

 

Good to know, thanks GSREP1, appreciate the feedback, it's crazy that no one has diagnosed and fixed this problem already--especially since it seems quite common in the GS. I'm leaning towards a problem with the heater core, but there is something that splits the heat that is making one side cold...just have to figure out what is reponsible for the split I guess and we'll have our answer....D

 

Now that it is warmer weather, I thought I'd check and see if anyone has a problem with one side of their car that doesn't seem as cold when the A/C is on. My refrigerant is fully charged and blowing cold on the driver side so that is not the issue, it's just not as cold on the passenger side as driver side, and it was definitely blowing cold in the winter on the passenger side when the heat was on. Thought I'd check to see if anyone has this fix and missed this when we were discussing the heating issue before I drop the $$ on that other servo motor.

 

Has anybody tried the auto-calibration????????????????

Its a piece of cake to do (non-nav cars).

Step 1.
Turn on ignition lights ONLY when holding the AUTO + RECIRC buttons together. Any error codes will appear. 21 & 24 will appear if it is dark out(solar sensor).
Step 2
Press RECIRC and let the system do the auto-calibration cycle. Let this run 2-3 times, turn ignition OFF then start her up and see if it works!!!

 

and what does this exactly do?

 

It re-calibrates all the blower speeds and position sensors on the directional motors!

 

Since this recalibrates blower speeds and sensors, would it have any effect on the actual temperature coming out of the vents? This is the problem we seem to be having--the temp is different from one side of the car to the other. I tried this and while it does seem to do exactly as you describe gs-ireland, I got a error code of 0 which I'm guessing means there is no issue with those functions-thanks for that input though, I'm sure you helped someone with that info...D

 

bump for new members and fresh eyes, I know it's cold again and their are some cold drivers or passengers out there besides me--maybe someone has the definitive fix....D

 

I was starting to think that i was the only guy with this issue. But my GS4 is only puming warm air to the passenger. the driver side vents are usaully shut and definetly the vent below the steering wheel.

 

do you have the vent on recirc or fresh?

 

while doing some work on my car i had the center console removed radio and ac controls...so after i put them back i wigged because the next time i used the ac the pass side blew hot air... so i went n checked all the servos and of course the pass side was stuck and not responding to the temp setting on the control... sure enough i checked the ac control unit and the harness on the right side looking at it form the front was loose.. i reseated it and my nice cold ac came back on on the pass side.. whew... cuz ac repairs are expansive

 

DruMnBaSS- is the harness easy to get to? I think that could be the solution to this issue. Can you post pictures of how it looks like and where it is at? I went to the dealer and they told me that it might be the servo...

Please email me at: my_fiveten@yahoo.com

Thank you,
Dennis

I had the opportunity to chat with DruMnBaSS, this is what he replied:

XxUnkN0vvNxX: grab the upper ac vent piece and evenly pull it out..
XxUnkN0vvNxX: pull out the ash tray
XxUnkN0vvNxX: and undo the 2 bolts up top and 2 on the botton
XxUnkN0vvNxX: radio and ac unit will come out together
myfive10: ok..same way when taking the stereo out right?
XxUnkN0vvNxX: check the harness
myfive10: ok cool...i have replaced my stereo..maybe that could be it
XxUnkN0vvNxX: very much so
myfive10: the harness is behind the ac control?
XxUnkN0vvNxX: yeah
XxUnkN0vvNxX: its the wire that you plug into it

Thanks again!

 

I actually changed one of the servo's already so I'm pretty sure I reseated everything correctly but I'll go back and check it out, I might have missed one, if not I'm definitely changing that other servo. I'll let you know what the result is...

 

I was having this problem last year going into this. I finally brought it to my mechanic last week and I have heat again. It turned out to be my heater core. No servo's or electronics. They just flushed my heater core and my heat came back. He said over a period of time sludge builds up in there. He flushed it but he said if it goes again he may have to change the core which is a big ticket job because he has to take down the dashboard.