sbrdd

Hello,
The problem I have with my ac is that it will cycle on and off if I turn it up above medium. However, even at medium eventually it cycles off for a bit and gives me the hot air treatment.

I've done my research or at least tried to and have the diagnostic codes of 21 and 24 from the ac in the car. However, I can't find any info on the code 24. (I did test the car in the sun for the solar sensor). So, I was wondering if you guys could help me out in figuring out what code 24 is. I've already ordered the part for the solar sensor from Carid.
Thanks

Lavrishevo

iTrader: (1)

Check this thread out. I believe 24 is rear solar sensor.

https://www.clublexus.com/forums/ls4...ditioning.html

sbrdd

Would that be the same solar sensor as the one I ordered? If so do I just order it and replace that as well?

Would you happen to know where the sensors are and how hard they are to replace.
P.S. Woiuld these sensors really cause the ac to shut on and off?
Thanks

Lavrishevo

iTrader: (1)

I don't know honestly but from the other thread it sounds like the compressor itself. This is the most common.

rkw77080

Lavrishevo

iTrader: (1)

Smoke sensor? That sounds interesting. Did not know I had one of those. What would be the purpose of that?

rkw77080

My LS430 does not have a rear A/C, but according to the repair manual, the smoke sensor is used to control the fresh air intake damper.

Lavrishevo

iTrader: (1)

Wow, impressive. I never knew my rear AC unit did so much.

sbrdd

Maybe I will have to just cough up the $140 for a diagnostic at like tire works or something.
Don't you have to replace the condenser, drier, and compressor as like one full unit instead of just the compressor.
(Pretty sure I read that somewhere)

rkw77080

sbrdd, here are the inspection procedures for DTC 1421 and 1424.

BradTank

To me it sounds like it's low on refrigerant.

I wouldn't think a solar sensor in the back for the auxilary rear air would be making warm air come out of the front vents.

When the rear AC is turned off, are you still experiencing warm air coming from the front vents?

I wouldn't buy any parts until I had confirmed the refrigerant levels.

sbrdd

I have checked the r134 levels. I refilled them and it is still doing the problem.
I don't think I have a rear compressor. But the problem is mainly that the ac will just cut off randomly.

rkw77080

How did you obtain these diagnostic codes (21 and 24), an OBDII reader? or directly from the car's display?

BradTank

The rear doesn't have a separate compressor, it does have a separate evaporator.

Did you or the dealership recharge the AC? It wouldn't surprise me if maybe an improper charge was put in as the UL's need more refrigerant than just the standard Lexus models as a result of the rear system.

I just went through this with my father, he had an Expedition that just never cooled well despite taking it to a Ford dealer numerous times. I put it on a set of gauges and it was clear it was low. I added a can of R-134 and it blows MUCH cooler now. I think they messed up and only charged it to the level of one without the AUX AC.

To really diagnose if you have a compressor problem, you need a set of manifold gauges that can read the high and low sides for pressure.

You usually don't have to replace the condenser, but the drier is usually done with the compressor. But if the compressor just destroys itself, sometimes it makes sense to just replace as much as possible because the whole system is filled with debris.

It also could have a good sized leak, another poster on here had a leak on the line that went to the rear evaporator from corrosion.

I think unless you already own all the AC tools, it probably makes sense to take it into a Lexus dealer to troubleshoot or maybe a shop that specializes in Car AC. I wouldn't take it to a chain outfit. The UL is a complex AC system on a somewhat rare car, I personally would be hesitant to take it anywhere but a dealer. You can pay them to diagnose it and then decide if you want them to repair it or you can tackle it yourself. I think it's worth the fee to not fly blind with it anymore.

Let us know when you figure it out.

milesdf

I had a similar problem with my 2004 LS 430.
Dealer replaced little motors in the dash that re direct air in the different settings.
Wish I could remember more!
Good luck!
Dave