2000 'Lara Heat Issue with Temp Control - Toyota Nation Forum : Toyota Car and Truck Forums

reidcc · 11-24-2010, 05:33 AM

Hello Folks-

I've been a Solara owner since end of March- when I bought a 2000 SLE with 130K on it(now has 149,500). I've also posted over on SG forums- but no answers.

During Spring- I noticed it had a slight heat issue- in that after 20 min warmup- the temp would regress back to cool air.
Well- now that its cold here in Northeast- I am noticing the same issues. I have the Auto temp Control with LCD Panel- and AUTO is not on, and does not seem to matter if Re-Circ or Outside Air.

After initial warm-up I get plenty of heat for 20 minutes(or so)- setting is 78 or 79. After that I get a sharp drop-off in temp, and if from floor vents, it may be cool, but if from the upper dash vent or defrost vent- its cold.
I did notice yesterday- driving that if I turned the temp up one degree at a time- it stayed cold all the way to 85 degrees. Once I turned the final step to where LCD said HOT- I got FULL Heat.

I've tried the internal Diagnostics on the LCD panel by hitting the re-circ and auto button while turning on ignition- and all lights go through their process, and then I get Code 21, which is Solar Sensor. The Solar Sensor is the passenger side on top of dash. I swapped out two of those from recently crashed Solaras, but I get the same code. Do I have the correct sensor?

The issue of no tempering or mixing of air- now that I think about- I had the same issue with the AC during the summer. Regardless of what Temp I had on the readout-if I turned the temp up a bit- I got no mixing in of warm air- only FULL AC. I never did try it all the way to HOT.

Could this be the LCD Module itself with its control? Or am I looking at a Sensor? Is Code 21- the Sensor up on top of right side dash?

I did see an on-line version of service manual somewhere- but had no information on the Auto Temp control version, only the Manual control version.

Any Help would be great-
Thank you
Chris

dug320 · 12-02-2010, 06:57 PM

I think I did reply on SG. Anyways.

A simple test of the sensor is to either disconnect it or short-it and see what happens.

There is also a temp sensor on the right side of the steering column attached to the lower panel (from memory I could be off a little) I would disconnect or short it and see what happens.

You should also look at the temp gauge. Does it move? One could consider the thermostat is the culprit.

When you adjust the fan speed do you think the fan changes speed? Does the fan run on lower speeds. This could be thermistor resistor that controls the fan speed.

reidcc · 12-03-2010, 05:47 AM

Thanks Dug-

Once my Temp guage comes up- it does not move- stays at the halfway point...very consistent. I nver even gave the thermostat any consideration- because the minute the knob is turned to "HOT" I get plenty of hot air. Move the knob just slightly so LCD says 85, and you only get slightly warm air.

Once temp comes up- I get plenty of hot air even when the LCD is set to 74 or 75, but after that 25 to 30 minutes has gone by- the output temp drops off quite a bit and car feels cool- again- even raising temp to 80.

I did pull the LCD readout unit 2 days ago, and unplug- only to see WHAT was behind there/ if any loose wiring or connections or anything like that. Once I plugged unit back in seemed like I got plenty of heat and good linearity as I changed temps, but once I went beyond that time threshold I mentioned-the same issue. I got a Code 21 again- during daylight.

I have read elsewhere that the right side sensor on top of dash is mainly for the autolamp function. Maybe the Heat and AC sensor is the left side?

Thx
Chris

My fan works on all speeds manually- I do not use the auto function.

reidcc · 07-31-2011, 09:28 AM

Help needed from someone on Climate Control

I brought this thread back from dead- because I've finally done some shot-gunning.

I found the LCD control panel for climate control for $30, and replaced it. It did no good and worked exact same. I then bought the thermistor sensor that is near right knee on lower valence panel lower dash. I upnplugged it, and had heat when set to 75- plugged back in and no heat so I replaced it. With the new one- works the same as before.

The only sensor left is on top of dash left side for solar load. I do not think thats it.

Today I looked under dash again- as I thought I noticed something when replacing the Thermistor. the other end of hose seemed to be open ended- or went nowhere. Looked close way under dash- and it appears fine- BUT I did notice a valve or motor control attached to the black box heat assembly that was doing nothing to turn as I increased the temp.

I assume this motor control opens and closes the blend door???

As I increased temp- one degree at a time- I heard no movement of the motor until I hit 82 degrees on the control- I could see the movement as well as the motor moved. When I moved it to 83- I saw the movement- as well as to 84, and 85. When I moved it to HOT- it seemed to move a huge amount.

I want to get in there and look at control- seems I need to get front part of console off first??? Does the entire console need to come out first?

Does anyone know if that control is getting signal from somewhere else besides the LCD panel????

I lived with this issue all winter and now I have no mixing even with AC on!!!

Thanks-
Chris

ThurzNite · 08-06-2011, 11:14 PM

Sorry for going slightly OT. Are you still getting error code 21?
I just ordered a FSM, damn thing was expensive from toyota!!!! But when I get it, I'll see if there's anything in there about the auto AC. Send me a PM in a week if not solved by then, k?
Dr J

ThurzNite · 08-06-2011, 11:27 PM

Just looked up the solar sensor, the parts diagram I'm looking at says it's on the left side the dash, driver side. I'll do a bit more digging.
Dr J

reidcc · 08-07-2011, 07:23 PM

Hi-
Yes I occasionally get Code 21. I would not worry about it though. When you run the diad test- make sure you are in the sun- or else you"ll get code 21. If you are in the sun- you should not get it.

I am still having issues. I've replaced the LCD control panel, the sensor above drivers right knee, the under bumper sensor, and the Solar sensor on left.

I created another thread entitled Auto Temp Control Blend Door Issues if U want a read.

Thx
Chris