I have 2003 Ls 430. Some times I noticed the ac doesn't cool and some times it is cool I turn it off. What could be the problem? I am the second owner. The compressor is already replaced. I went to a mechanic and he hooked up to the computer and check the code. It said something max damper sensor and asked me to read it here, The mechanic says there is some issue with damper motor or sensor which requires him to remove all the dashboard. Is this the real issue. Sorry, I am not a mechanic but the damper only controls the volume of air, not the hotness or coldness. In my car the air flow is decent but sometimes it blows hot air. Kindly please help me resolve this issue

 

guys need your advice.It happens only sometimes

 

A very common symptom is that our cars will lose a small amount of coolant. At a point the AC will run hot / cold with no real pattern to track.

I say this over and over but please be sure to top off the coolant in radiator but likely the reservoir is low. I bought a replacement radiator cap and reservoir too for my car. I also replaced the small black lines. I think they are known to swell and leak a small bit too -but very hard to trace. These cars are all aging so seals are naturally drying out a bit each year - top off the coolant and test!

 

okay. I will ask my mechanic to check to top up coolant in the radiator. But when i run the diagnostic check, I get an alarm of cold air bypass damper.

 

Is the temperature relatively the same out of the driver and passenger vents?

 

The driver side and the front passenger side are at same temperature and even the vents at the back of the centre console.However the vents at the back at the side doors blow hot air, when I switch on the rear ac

 

I filled up the radiator with coolant.Let me see if there is improvement . From what I have read the pressure switch is a common issue. Does this fault show up when you connect the controller and v see the codes

 

Check your refrigerant levels if your AC doesn't cool. The procedure is:
1) Open your hood, run the engine at 1500rpm
2) Set front and rear blower speed to highest speed
3) Set front and rear temperature to MAX COOL
4) Fully open all 4 doors
5) Look at the sight glass on the liquid tube of your AC line (car's lower LH side, in front of the radiator)

Possible results:
1) Bubbles in sight glass => insufficient refrigerant. Run leak detection on entire AC system, repair lines as needed, then add refrigerant until bubbles disappear
2) No bubbles in sight glass => inconclusive, refer to results 3 and 4
3) No temperature difference between compressor inlet and outlet => zero or near zero refrigerant. Leak detect, repair lines as needed, then add refrigerant until bubbles disappear
4) Temperature difference between compressor inlet and outlet is noticeably different = correct or too much refrigerant, refer to results 5 and 6
5) Immediately after AC is turned off, refrigerant in sight glass remains clear => too much refrigerant. Discharge refrigerant (legally!), evacuate air, charge proper amount of purified refrigerant
6) When AC is turned off, refrigerant foams in sight glass then stays clear => correct amount of refrigerant.

You can also inspect refrigerant pressure using a manifold gauge set. The specified test conditions are temperature at 30-35C, air inlet set on RECIRC, engine at 2000rpm, blower speed at HI, temperature set to COLD. Then a normally functioning system will read 0.15-0.25 MPa on the low pressure line, and 1.37-1.55 MPa on the high pressure line.

Insufficient cooling can be caused by:
* Refrigerant line leaks
* Dirt in the receiver obstructing refrigerant flow
* Faulty expansion valve
* Dirty condenser
* Air in the refrigeration system
* Dirty or insufficient compressor oil (PAG 46 is what my Lexus dealer used)
* Leaking compressor

After 11 years in Canada, my LS430 developed corrosion in the high pressure line running to the rear AC evaporator, causing gradual loss of refrigerant over the few years prior before the AC stopped cooling at all. If this is your problem, see https://www.clublexus.com/forums/ls-...sure-line.html on how to fix it yourself. It will run you 7-8 hours of labor at Lexus, plus a few hundred for parts and AC system recharge.

 

Thanks a lot Stan for your detailed explanation. I showed the car to my electrician .He checked with the pressure gauge and found the press at low side at 70 psi which is not normal.I changed the compressor and the cooling seems good till now. I need to monitor for few days to check. I'll update you guys after few days.