Climate Control Issue, 40th Anniv.

[BoneDragger]

So now that I have properly introduced myself in my first post, please allow me to post my first request for trouble shooting assistance.

I (or should I the "ride") is having an intermittent non-functioning climate control.

When the weather is very warm, 90+ degrees (as it is iAn Coastal GA now) I get no function from the climate control unit. The only lights that come on are the upper row, directional buttons and the lower row, fan buttons. Now fan is blowing and there is no engagement/clicking at the A/C unit. Once the temp drops below say 90 or upper 80s, everything works great.

So I have search the forums here and I have removed, disassembled the dash control unit and the A/C amp. Neither have helped the problem. By the way the posts were all very usefully in directing me to these items and what to try. When the unit does work it all works perfectly.

From previous experiences around vehicles my assumption is some circuit or relay or such is temp sensitive and thus prevent unit from receiving all power, etc.

So what is next? Please someone tell me that there is a "small relay" or such to find and replace and not that I have to replace the control unit or worse the A/C amp

If i still lived in Durango I wouldn't need no stinking AC (but I guess I would need the heat by winter)

The Bonedragger

 

[Dissent]

I would pull out the A.C. Amplifier and clean it with some specialized electronics cleaner. Odds are some water got in there and corroded the circuit board. My 97 LX450 has it just above the accelerator pedal. I had my windshield tinted with 50% film to block heat and they soaked the dash and put 1" of water in the amplifier because it took 3 attempts to get the 1 piece film to install correctly. Same indicator lights. Took 10 min to fix. Good luck.

 

[Dragos80]

Don't forget to check the plug behind the dash. Also look for the white flexible hose, it should also be plugged in the "sensor hole" in the lower left corner.

 

[Dissent]

If you need to replace the A/C amp, pickup a used one. Typically they are $25-$40 from a part out. New is like $450 and it's the most basic circuit board in a plastic box. Grab a spare if you can. The Lexus LX450 and the Toyota 40th Anniversary are the same truck with the auto-temp air conditioner. The other Toyota LC models don't use the same type of amp.

 

[bloc]

For the record there are two AC amps on auto AC rigs.. the mentioned one above the accelerator and another smaller unit behind the glove box. That one is black with a multi-wire plug pointed upward

 

[Dissent]

For the record there are two AC amps on auto AC rigs.. the mentioned one above the accelerator and another smaller unit behind the glove box. That one is black with a multi-wire plug pointed upward

Very true. FWIW, I've not seen the one behind the glove box have that water issue. The accelerator pedal one is facing straight up with no cover, like a cup. Interesting design given all the windshield leaks.

 

[Celebran2]

Those are becoming far too rare. I had mine go after a windshield leak last year. Could only find used on mud for 200-400$ and they don't make them anymore, at least my parts guy couldn't find any.
Just to note the HDJ81 JDM models that had climate control will have the same motherboard in it, just with a different part # and a different white box. Swap the motherboard and you are good to go.
Also, consider modifying the plastic box it sits in by drilling a small hole in the low corner. Lets the water drain if it does end up there, possibly saving the electronics.....

 

[BoneDragger]

UPDATE, AND FOLLOW-UP QUESTION

Hey everyone, I truly appreciate all the suggestions. Let me get you all up to date on what I have done, etc.

Both control unit and the A/C Amp have been pulled and clean. No corrosion or water or dirt, all was amazingly clean. I have been careful to be sure the hose is back on when reinstalling.

I have not looked at the black box behind the glove box yet, that is for today.

The issue truly appears to be heat related, i I park in the shade, leave windows open, etc. and the temp is 90 or less, it works every time and works Great.

So after I check and clean the black box, and if I find nothing apparent, which item should I look at replacing first based on my diagnoses in regards to being Heat sensitive? The A/C Amp or dash control unit?

Thanks again for all your input.

The BoneDragger (aka Dan)

 

[BoneDragger]

UPDATE, AND FOLLOW-UP QUESTION

Hey everyone, I truly appreciate all the suggestions. Let me get you all up to date on what I have done, etc.

Both control unit and the A/C Amp have been pulled and clean. No corrosion or water or dirt, all was amazingly clean. I have been careful to be sure the hose is back on when reinstalling.

I have not looked at the black box behind the glove box yet, that is for today.

The issue truly appears to be heat related, i I park in the shade, leave windows open, etc. and the temp is 90 or less, it works every time and works Great.

So after I check and clean the black box, and if I find nothing apparent, which item should I look at replacing first based on my diagnoses in regards to being Heat sensitive? The A/C Amp or dash control unit?

Thanks again for all your input.

The BoneDragger (aka Dan)

So now I have removed and cleaned the black control box behind the glove box, still no change.
When the cab temp is high from sitting in the hot sun, especially closed up windows and all, it will not work.

Additional information- when this happens on the lights on the dash control unit that "light up" are the zone buttons and the fan speed buttons, but on the lights light, there is no action from pushing any buttons.
with all of this I'm leaning towards finding a A/C Amp unit.

Any additional thoughts from anyone?

Thanks,
Bonedragger

 

[kruisinkid]

the control unit is completely "dumb" meaning it is literally just buttons, leds and resistors. no logic to fry. the white boxed amp, did you remove the PCB from the box and get a good look at both sides? could it be your engine temp sensor for the a/c system is dying and it thinks the engine is too hot and thus not letting you run the a/c?

 

[bloc]

There are three temp sensors.. one in the grille inside a round protective housing, one behind the small grate to the left of the temp slider (this one is in the end of the corrugated tube. The other end of thattube sits near a foot blower and acts as a Venturi to pull cabin air over the sensor), and one on the heater core. Actually I guess there is one on the evap core but all cruisers have this and it doesn't often seem to be a problem.

I guess you could get an EWD and ohm all of these out to see if they are causing issues..

 

[kruisinkid]

i think there are only 3 according to the EWD. engine coolant temp sensor, room temp sensor (the white tube sensor which controls the a/c if in auto mode, and the ambient temp sensor below the grille. there also is an engine coolant temp switch that runs the coil of the coolant temp cutoff relay. but yes i would get the LX450 EWD asap

 

[LINUS]

Try this, worked in my old 40th:

"Auto" climate control - hearing a 'thump' from inside heater box...

Give @SUMMIT CRUISERS props for getting at it prior to me, it was our fix.

 

[bloc]

i think there are only 3 according to the EWD. engine coolant temp sensor, room temp sensor (the white tube sensor which controls the a/c if in auto mode, and the ambient temp sensor below the grille. there also is an engine coolant temp switch that runs the coil of the coolant temp cutoff relay. but yes i would get the LX450 EWD asap

There is a sensor of some type on the bottom of the heater core (plainly visible IIRC). This may be the "water temp sensor" in the 97LX EWD I'm looking at. Note that it has different wire colors and designation (W5) than the "engine coolant temp sensor" (E3) on the Engine Control EWD. There is a "thermistor" too but i can't remember where it is. The one I'm thinking of on the Evap core?

Appears there is a solar sensor as well.. possibly OP's problem?

 

[kruisinkid]

gotchya. the solar sensor is only on the lexus trucks i believe. 40ths dont have it. it would be on the passenger top side of the dash up against the windsheild. yeah i would bet that sensor on the heater core is the coolant temp sensor. good place for that. perhaps that wiring got corroded and shorted. sounds like something is expanding due to the extreme heat of a parked car.

 

[Dissent]

I'd still clean that amp thoroughly with some circuit cleaner.

 

[BoneDragger]

There are three temp sensors.. one in the grille inside a round protective housing, one behind the small grate to the left of the temp slider (this one is in the end of the corrugated tube. The other end of thattube sits near a foot blower and acts as a Venturi to pull cabin air over the sensor), and one on the heater core. Actually I guess there is one on the evap core but all cruisers have this and it doesn't often seem to be a problem.

I guess you could get an EWD and ohm all of these out to see if they are causing issues..

bloc, thanks for this. When I contact cleaned the control unit and the Amp, I did spray the sensor in the control unit that the corrugated tube attaches to. I'll track down the other end of that tube and look for that. Since all my issues revolve around cabin temp (at least it sure appears that way) I assume you are thinking one of these sensors if too hot might be interrupting an electrical signal.

Question, to all out there, has anyone ever replaced one of these?
Also anyone have a link to an EWD for the A/C and what I'm working on?

Thanks.

 

[bloc]

bloc, thanks for this. When I contact cleaned the control unit and the Amp, I did spray the sensor in the control unit that the corrugated tube attaches to. I'll track down the other end of that tube and look for that. Since all my issues revolve around cabin temp (at least it sure appears that way) I assume you are thinking one of these sensors if too hot might be interrupting an electrical signal.

Question, to all out there, has anyone ever replaced one of these?
Also anyone have a link to an EWD for the A/C and what I'm working on?

Thanks.

Best way to find EWDs: google "site:ih8mud.com FSM hell of a price"

I wasn't aware that Anniv editions didn't have the solar sensor, so there are some differences between yours and the LX, but most of the auto components will be similar. Wire colors may not, however.. but I don't know how you'll find an anniv edition manual.

Also, the other end of the corrugated tube not being in place shouldn't matter for your issues. It only serves to draw cabin temp air over the cabin temp sensor while the AC is operating.. if it simply refuses to work above a certain temp I'm thinking the problem isn't this tube.

And yes.. if it seems like there's a definite temp cutoff personally I'd wonder about one of the temp sensors inside the cabin. That doesn't rule out a connection issue somewhere else, maybe even a fuse loose in a holder (different parts of the AC system may get power at different times (ign vs acc, for example) through different fuses.