What Does Ac Code 33 Indicate?

[semlin]

hi folks, my first post here. looks like a good community. I'm hoping you can help me with an ac problem.

I just bought a 1991 ls400 with 133k miles that has been sitting for 3 years due to owner's health and has done less than 5000 miles in the last 7 years according to Lexus service mileage records. It has an undated r134a conversion sticker indicating a no lexus shop converted it and added 29 ounces of r134a and 4.5 ounces of oil to it. The owner's wife cannot find the receipts and all she can say is that was more than 3 years ago.

the AC light works and does not flash but turning it on makes no difference to the temp coming out of the vents.

I also pulled the ac trouble codes using the instructions here.

http://www.lexls.com/tutorials/air/accodes.html

I get code 33 which apparently means "Open in air mix damper position sensor circuit. Or, open or short in air mix servomotor circuit. Or, air mix servomotor locked."

my first question is is this a normal code for a system that is low on coolant or is that an indication of a specific problem and, if so, what problem?

my second question is whether 4.5 ounces of oil sounds right to you? I would have though more like 8 ounces from limited experience with other systems.

You cannot buy r134a do it yourself kits in canada so I need to get an AC tech to look at this. I had been thinking I would try topping it up with coolant and dye first to see if that is the problem. Now with this code I am not so sure and I am also wondering whether to tell the guy to add some oil. any help is much appreciated.

[semlin]

well i googled "air mix damper position sensor circuit" and found a link to a japanese patent from the mid 80s as follows:

"An automotive air conditioning system is provided which includes a damper position control device which controls the angular position of an air mix damper. The air mix damper controls the mixture of cool air and heated air to thereby control the temperature of air blown into a compartment by the air conditioning system. The damper position control device further includes a motor actuator which drive the air mix damper and a control circuit. The motor actuator includes a drive motor for the air mix damper and a rotation control device including a regulator which regulates the upper and lower rotational limits of the shaft of the drive motor and a position detector which detects the rotational angle of the shaft. The control circuit controls the motor actuator in accordance with a plurality of detected signals, such as an inside temperature signal, an outside temperature signal, etc. The control circuit is also responsive to position signals generated by the position detector which correspond to the upper and lower limitation of the rotational angle of the motor. The control circuit initiates control of the operation of the motor actuator upon inputting one of the position signals corresponding to the upper and lower rotational limits. The control circuit then determines whether the motor stops within the range of the upper and lower rotational limits. A signal from the position detector at the position at which the motor stops is used by the control circuit as one of the rotational limits of the regulator."

http://www.freepatentsonline.com/4840308.html

from this i infer that part of this doodad is the regulator that cycles off the compressor when the drive shaft rpm exceeds minimum or maximum tolerances. hopefully this code just means the compressor has shut down due to insufficient coolant impacting drive shaft rpm.

[jurnaza]

I am also having this problem. I recently purchased a 1991 LS400, the previous owner had the compressor replaced a year ago along with a recharge and had since left the car sitting. Now one year later the AC blows hot air and is throwing the error code "33". Which after some hunting I found out to be "Air Outlet Door Position Sensor Circuit".

Can anyone point me in the right direction to troubleshoot this error code 33?

Thanks,

New Lexus Owner & Proud Toyota Owner

Jeff