cfiredog

I have a 1998 GS400. I just started having problems with the HVAC not working this morning. I started the car, and noticed the outside temperature display was showing "--" , which I have never seen before (It usually reads the temp in my cold garage about 46 degrees F). I turned on the HVAC by pressing the auto button and nothing happened, I then adjusted the fan speed manually and still nothing. I also tried lowering the temperature and trying different modes, but the fan would not come on. Has anyone had this happen before? or can you point me to a previous post? Any help would be appreciated...not looking forward to the cold drive to work.

TRD911

Sounds like a fuse. I would check fuses to see if any are open.

Maybe you could try to reset by disconnecting the negative terminal of the battery for two minutes.

Let us know what you find.

cfiredog

I pulled the fuse and gave it a good look;it was still closed. It was getting late so I went in for the evening. This morning when I went to work every thing was working as normal. So I am not sure if it was the pulling of the fuse that reset "something", or if it was just a fluke occurance in the first place??? Thanks for your suggestion.

quy2k

Funny thing is, I had the exact same problem this morning. I turned the car off, and restarted it, and then it worked... I foresee this will be a recurring problem tho... Anyone have any suggestions? It's winter here, and it can get really cold!

Lubs

I'm having this same problem. It has happened twice, a few weeks apart from each other. The problem persisted until the next morning, when everything returned to normal.

Both times I didn't really notice, because the car heated up normally. Only when I got close to my destination did I realize the heat had stopped working.

Lubs

I had the temperature not register again this morning. It did come back for most of the ride, but it seems it's going to be a recurring problem. Can someone point me to where I can find the temperature sensor, I want to check it out.

3UZFTE

Try checking the system for DTCs, press and HOLD BOTH "Recirc/Fresh" and "AUTO" buttons at the SAME time, WHILE the ignition switch is turned to the ON position. The HVAC panel will blink all leds 4 times, then will display your DTC codes if any, then compare to the HVAC DTC chart. Codes 21 and 24 are both common if doing the test in a dark or dimmly lit area, if no codes pressure any botton to exit. If it consist, bring it to your place of service.

PS. The ambient temp sensor is on the front hood support, behind the grill infront of the radiator. The cabin temp sensor is by your right knee underneath the ignition switch.

Lubs

Thanks for the help 3UZFTE.

I got four codes from the HVAC panel. 21, 24, 42 and 99. I can't find a list of what these codes mean.

I checked the A/C fuse, and it's not blown.

I can't find exactly where the OAT sensor is. I sprayed the hood latch assembly with WD-40 a few weeks ago because it was sticking and my hood wouldn't close. I hope I didn't damage the sensor while doing that. There has also been a lot of snow here recently, and it has been packed into the grille. Maybe that somehow damaged it, or affected the connection.

Any suggestions for me? I'm surprised there's no override to allow for manual control of the HVAC system.

Any suggestions?

xhackr

21 - solar sensor (passenger) – normal if not receiving light.
24 - solar sensor (driver) – normal if not receiving light.
42 – air inlet damper control servomotor circuit / air inlet damper position sensor circuit
99 – Sorry, no listing in AllData

3UZFTE

42, like he said is a problem with your "air inlet damper control servomotor", which is no cake walk, it will require some wire tracing and testing circuits and motors. Check the sensor, motor, harness, and AC amplifier could all be trouble areas.

Code 99 - Multiprex Communication circuit - Open in Multiprex Comm. circuit... I don't have any idea what that it.

I assume you don't have the 3 volumes of rapair manuals, I'd take it to the dealership if I were you.

Lubs

Just to update on this issue...

I took the car in to get checked out, and of course the problem had disappeared. It has recurred once since then. Replacing the air inlet servo motor was considered, but there's no guarantee whether that was the problem or not.

Everything has been running good for over a week, so I'm keeping my fingers crossed that it has fixed itself. Will update as necessary...

3UZFTE

Thats relatively good to hear

e-man

I know I'm bumping an old thread, but this is so weird. My hood latch cable was stuck, so I sprayed some WD-40 on the latch. Within a few days, I heard a tapping noise (like a baseball card in a bicycle spoke) and within 2 weeks my a/c went out. I got a code 42 when I ran the diagnostics. My dealership told me that I needed to replace the compressor because I had bad read valves (whatever that means). Code 42 has something to do with the inlet servo motor (or something like that). Is this the same as a bad compressor? Any help would be greatly appreciated.

e