jefflex400

The AC panel on the dashboard of my 1996 400 LS normally shows the temperature which I have set the drivers and passenger side temperature to. For example, the panel normally reads 76 for both driver and passenger side. Suddenly the panel no longer displays the temperature I have set the system to, instead it reads COLD on both the driver and passenger side. The AC blows cold but the automatic regulation is no longer working. The only way I can regulate the temperature is to manually turn the AC on and off periodically otherwise with the AC on the cabin gets too cold after a while. Does anyone have any ideas on what the problem is? Thanks in advance, Jeff

timmy0tool

iTrader: (7)

so when you press the temp up and down buttons, do you get no response?
"COLD" means the temp is set to the lowest number. pressing up should restore the numbers accordingly which is the normal function of the auto climate control.

jefflex400

Yes, that is correct... I get no response... when I use the button that I normally use to adjust the temperature up or down, the display still shows COLD.

jefflex400

I have also been chasing a battery drain issue that may be related to the problem with the AC display. I am wondering whether there is a problem with the AC control panel on the dash that is causing my battery to go dead. I figure it is a long shot but I am wondering if anyone else on this forum has experienced a similar issue, that is, a problem with the AC control panel causing a battery drain when the engine is not running.

spuds

No,but had a jetta with a bad diode on alternator.And it tested good.Oh no no no said the board,its diodes.So I replaced it with one rebuilt with super diodes,sho nuff,that was the problem.Turned out that was a big failure on that car.
May not apply here to a lexus(IDK),but good general knowledge to file away anyhow.

Oh,it is your thread.Bringing up a different issue confused me.

Banshee365

With the ignition in the OFF position, press and hold the REC and AUTO buttons together on the AC unit and turn the ignition ON. First the indicator lights will test then the unit will go into a self diagnostic mode. Report back with any numbered codes given. Note that you will get codes 21 & 24 if you are doing this test as night as those are codes for each of the solar sensors. If they aren't receiving sunlight during the test the unit throws codes for them.

As far as how to see if your AC amplifier is draining your battery, here is how you do that. If you have a DVOM you will be able to see this faster than just trial and error. This method is also how you kill power to the AC amplifier to clear diagnostic codes. The AC amplifier receives it's power through a fuse that is located in the passenger compartment just behind the parking brake pedal. Under the fuse box cover look for a 15A fuse labeled 'FUEL OPEN.' Remove that fuse and you remove power from the AC amplifier.

If you have a DVOM, before pulling this fuse, disconnect your ground cable from your battery. Put your DVOM in AMP mode. With the doors shut and all lights off hold one lead to the negative battery post and the other to the negative battery cable. Note the amperage that is showing. That is the parasitic draw. Generally, anything less than 50mAh is okay. Then, remove the 'FUEL OPEN' fuse under the dash. Repeat the test. If the amperage drops significantly you know you may have an issue with your AC amplifier. These units are best sourced from your local u-pull-it yards. This parasitic draw test is only as accurate as you perform it. Make sure the conditions are identical each time. Don't do one with the door open and the other with the door off as lights are a huge draw respectively.

jefflex400

Banshee365, many thanks for your suggestions. I will see if my digital multi-meter is suitable for the tests you recommended. Jeff