Automotive Air Conditioning Information Forum

Hello,

I have a 2001 Lexus GS300

I replaced the compressor, expansion valve, condensor, and pressure switch with Denso products. I added 1.3oz of oil to the system for the new condensor and the compressor already came pre-oiled. Flushed, vacuumed and recharged with 600g of freon per the service manual. However, when I turn the AC on, the light on the AC button immediately flashes and switches my compressor off. This tells me it either has too much or too little freon or oil. I'm puzzled and don't know what the next step should be. When I attempt to charge it, the machine will get stuck at 475g for a minute and then proceed to add to 550g. It'll sit there for a moment as well and then finally charge to 600g. I've done this 3 times and still get the same issue. I've tried only 550g and no luck as well. I thought about bypassing the switch but don't know how to do that on a 4 prong toyota switch. My pressure readings read 40psi low and about 150 high when the conpressor kicks on for a second. When charging, my low side goes up to 80psi and the high is at 100 with the car off.

Code 23 which is pressure switch circuit.

Any thoughts and ideas would be greatly appreciated.

A blinking A/C-switch light on a Toyota product means that a difference in RPM exists between the engine and compressor. The blinking light further indicates that the compressor's drive belt is slipping and that it is momentarily seizing or has completely seized. The question is, why?

From your description, it sounds like you might have put-in too much oil. According to the specs that I have, the 2001 Lexus GS300 holds a total of 7.0 fluid ounces of PAG-46 oil. I don't know how much oil the new compressor contained, but my guess is 7 ounces.

If you didn't take into account the amount of oil already in the system: Evaporator (~1.5 oz.), receiver/dryer (~2 ozs.), and hoses/lines (~0.5 oz.)—for a total amount of ~4 ounces—plus the 1.3 ounces that you put into the new condenser—you should have drained the new compressor of oil and put back in only about 1.7-2.0 ounces. So you might have as much as 5.3 ounces too much oil in the system, which would certainly be enough of an overage to cause the blinking-light and system-shutdown problems you described.

Also, what do you mean that you flushed the system?

The refrigerant specification that I have for your car is 21-23 ounces net weight (600-652 g.) of R-134a. Did you charge the system with the engine running at ~1,800 RPM and the compressor engaged? If the engine was at idle or shut off, that would explain the difficulty you had in charging it.

JohnHere wrote: ↑Thu May 02, 2024 8:25 pm A blinking A/C-switch light on a Toyota product means that a difference in RPM exists between the engine and compressor. The blinking light further indicates that the compressor's drive belt is slipping and that it is momentarily seizing or has completely seized. The question is, why?

From your description, it sounds like you might have put-in too much oil. According to the specs that I have, the 2001 Lexus GS300 holds a total of 7.0 fluid ounces of PAG-46 oil. I don't know how much oil the new compressor contained, but my guess is 7 ounces.

If you didn't take into account the amount of oil already in the system: Evaporator (~1.5 oz.), receiver/dryer (~2 ozs.), and hoses/lines (~0.5 oz.)—for a total amount of ~4 ounces—plus the 1.3 ounces that you put into the new condenser—you should have drained the new compressor of oil and put back in only about 1.7-2.0 ounces. So you might have as much as 5.3 ounces too much oil in the system, which would certainly be enough of an overage to cause the blinking-light and system-shutdown problems you described.

Also, what do you mean that you flushed the system?

The refrigerant specification that I have for your car is 21-23 ounces net weight (600-652 g.) of R-134a. Did you charge the system with the engine running at ~1,800 RPM and the compressor engaged? If the engine was at idle or shut off, that would explain the difficulty you had in charging it.

Hello, thank you for the detailed response!

Too much oil is what I immediately thought as well but wanted to get an experts opinion!

I flushed the the lines and the evaporator by using the A/C Certified Pro Flush System Cleaner Aerosol Spray 17oz kit from an autoparts store. Sprayed it through the low line and it circulated and sprayed out the high line. I already had the compressor and condensor remove before i flushed the lines and the evaporator.

Once the flush was done, I used compressed air to get the excess sprayed out until I couldn't see anything coming out. Then I installed the compressor, condensor and expansion valve and vacuumed the system and proceeded to charging. The dryer is actually built with the condensor so that is new as well.

For some reason I thought the AC compressor came with only enough oil for the unit itself but that would make sense if it has 7oz like you stated.

What would be the best approach? I do not have any confidence on how much oil is in the system at this point. Should I remove the compressor, dump the oil and then add accordingly? How much should I add? This is what the math tells me.

Example:

Added from previous attempts 1.3oz.
Ac compressor pre oil amount: 7oz
Evaporator core: 1.5oz
Lines: 0.5oz

Total amount: 10.3 oz of oil

Dump the compressor oil: 7 oz hopefully
Remaining amount 3.3oz
Add 3.7 oz

Does this seem the right approach?

I charged with the vehicle off. I will attempt it at 1800 rpm next time as reccomended.

Thank you!

Octaneskrrt wrote: ↑Fri May 03, 2024 6:40 am For some reason I thought the AC compressor came with only enough oil for the unit itself but that would make sense if it has 7oz like you stated.

That might be where you went wrong. Some compressors come filled with enough oil for the entire system, and some come dry.

Octaneskrrt wrote: ↑Fri May 03, 2024 6:40 am What would be the best approach? I do not have any confidence on how much oil is in the system at this point. Should I remove the compressor, dump the oil and then add accordingly? How much should I add? This is what the math tells me.
Example:
Added from previous attempts 1.3oz.
Ac compressor pre oil amount: 7oz
Evaporator core: 1.5oz
Lines: 0.5oz
Total amount: 10.3 oz of oil
Dump the compressor oil: 7 oz hopefully
Remaining amount 3.3oz
Add 3.7 oz
Does this seem the right approach?

It's much more difficult now that we really don't know precisely how much oil the system contains. We could resort to sheer guesswork, which of course could result in over-filling or under-filling the system.

The better approach (albeit the hardest as far as the work involved is concerned) would be to re-flush the evaporator (not including the compressor, condenser, TXV, lines and hoses, and the integral R/D; the latter would have to be replaced again). And starting with a mostly "dry" system, either put all the oil (5.5 ounces) in the compressor, allowing for the ~1.5 ounces of oil already in the condenser—or, you could oil-balance the system. By that I mean add 1.5 ounces to the flushed evaporator, 1.5 ounces to the new R/D, and 2.5 ounces to the drained compressor. Remember that we already have an additional 1.5 ounces already in the new condenser.

JohnHere wrote: ↑Fri May 03, 2024 3:01 pm

Octaneskrrt wrote: ↑Fri May 03, 2024 6:40 am For some reason I thought the AC compressor came with only enough oil for the unit itself but that would make sense if it has 7oz like you stated.

That might be where you went wrong. Some compressors come filled with enough oil for the entire system, and some come dry.

Octaneskrrt wrote: ↑Fri May 03, 2024 6:40 am What would be the best approach? I do not have any confidence on how much oil is in the system at this point. Should I remove the compressor, dump the oil and then add accordingly? How much should I add? This is what the math tells me.
Example:
Added from previous attempts 1.3oz.
Ac compressor pre oil amount: 7oz
Evaporator core: 1.5oz
Lines: 0.5oz
Total amount: 10.3 oz of oil
Dump the compressor oil: 7 oz hopefully
Remaining amount 3.3oz
Add 3.7 oz
Does this seem the right approach?

It's much more difficult now that we really don't know precisely how much oil the system contains. We could resort to sheer guesswork, which of course could result in over-filling or under-filling the system.

The better approach (albeit the hardest as far as the work involved is concerned) would be to re-flush the evaporator (not including the compressor, condenser, TXV, lines and hoses, and the integral R/D; the latter would have to be replaced again). And starting with a mostly "dry" system, either put all the oil (5.5 ounces) in the compressor, allowing for the ~1.5 ounces of oil already in the condenser—or, you could oil-balance the system. By that I mean add 1.5 ounces to the flushed evaporator, 1.5 ounces to the new R/D, and 2.5 ounces to the drained compressor. Remember that we already have an additional 1.5 ounces already in the new condenser.

So the only way I can flush the evaporator (behind the dash) is flushing through the lines that are connected to the condensor and compressor. I just disconnect those and cycle through the lines, evaporator and expansion valve. If I remove the expansion valve it would allow the flush material to get all over the floor board on the driver side. The alternative is to remove the dash which is pretty labor intensive on this car and was hoping I could avoid that. But if that's what needs to be done then so be it! Thoughts?

Also, when I added the 1.3oz of oil, it was through the AC shop machine that was connected to the low and high side. Is it correct to say the condensor has 1.3oz? Just want to confirm.

Just a side note I forgot. Everytime I pulled vaccum it would also recover oil. In total it was 1.2oz it recovered according to the machine.

Thank you so much for your responses. I will remove the compressor and proceed to flush the system once again. Not including the condensor unless otherwise stated. I am traveling to Chicago but once I get back I will attempt this and get back to you with my results.

Octaneskrrt wrote: ↑Sat May 04, 2024 5:15 am So the only way I can flush the evaporator (behind the dash) is flushing through the lines that are connected to the condensor and compressor. I just disconnect those and cycle through the lines, evaporator and expansion valve. If I remove the expansion valve it would allow the flush material to get all over the floor board on the driver side. The alternative is to remove the dash which is pretty labor intensive on this car and was hoping I could avoid that. But if that's what needs to be done then so be it! Thoughts?

You can't flush the evaporator with the TXV in place because it won't allow much, if any, of the flush solvent through the valve's small orifice. You would have to remove the TXV beforehand so that you'll have an unrestricted path for the solvent through the evaporator.

If you can get at the inlet and outlet tubes of the evaporator without removing the evaporator from the dash, you should be able to press (using finger pressure) clear plastic tubing onto both of the metal tubes coming out of the evaporator—you'll need two different sizes of plastic tubing for this purpose—and direct the stream of the flush solvent into a bucket or washtub to avoid the mess inside the car. If this isn't possible, then I'm afraid you'll have to remove the evaporator from the dash.

Octaneskrrt wrote: ↑Sat May 04, 2024 5:15 am Also, when I added the 1.3oz of oil, it was through the AC shop machine that was connected to the low and high side. Is it correct to say the condensor has 1.3oz? Just want to confirm.

When you mentioned "machine," do you mean a Recover/Recycle/Recharge (RRR) machine? If so, and you added 1.3 ounces of oil via the RRR machine, it's hard to say where it went.

If the car were mine, I would "assume" that the relatively small amount of oil went into the condenser and integral receiver/dryer. And since the desiccant bag in the R/D will have to be replaced again, and you plan to solvent-flush the evaporator, let's assume (there's that word again) that both will be free of any oil. So where does that leave us?

Filling the compressor with 6.5 fluid ounces of oil, reassembling the system, evacuating, and recharging, will get you very close to the correct amount of 7 fluid ounces total—maybe a little over, which won't hurt anything IMHO. I think that's about as close as we're going to get under the circumstances.

Octaneskrrt wrote: ↑Sat May 04, 2024 5:15 am Just a side note I forgot. Everytime I pulled vaccum it would also recover oil. In total it was 1.2oz it recovered according to the machine.

Okay, 1.3 ounces "in" versus 1.2 ounces "out" is essentially the same. Therefore, I would amend the amount needed to 7 fluid ounces (the original amount called for in the specs) put into the empty compressor, not worry about oil-balancing, and call it done.

JohnHere wrote: ↑Sat May 04, 2024 9:43 pm Okay, 1.3 ounces "in" versus 1.2 ounces "out" is essentially the same. Therefore, I would amend the amount needed to 7 fluid ounces (the original amount called for in the specs) put into the empty compressor, not worry about oil-balancing, and call it done.

Hey boss so I finally evacuated the system, emptied the compressor, and recharged with new oil. Unfortunately, I got the same result as last time.
I charged it with the car running and above 1800rpm this time per your recommendation. I noticed the AC clutch would immediately kick OFF after a couple seconds during the charging process. I let it fully charge and of course same results.

I evacuated the system once again and this time only charged it to 200g of freon just to confirm if the AC compressor would shut off even with low freon in it. Unsurprisingly, the compressor shuts off even with a low amount. I turn it back on and it immediately kills the compressor. Correct me if I'm wrong, but this wouldn't be an exceeding pressure indicator to shut it off by the pressure switch since I haven't even charged the system over 33% of the total amount. I went ahead and proceeded to fully fill and bypassed the AC relay this round. The result? Cold air no problem.

So I'm wondering if it has to do with the RPM speed sensor. The car was swapped with a JDM engine so I am not sure if the output values from the speed sensor or tachometer translate correctly to the japanese ecu. The engine is the 2JZGTE instead of the US 2JZGE non turbo. I'm not sure if the ecu reads these values and causes the fail safe to occur. I wanted to look up the OHM, Voltage, and frequency values of the compressor side and also see what the connecting side is reading. Maybe I need to add a resistor or something if values differentiate?

Also, is it possible to bypass the ac speed sensor?

Thank you!

That 'Code 23-Pressure Switch Circuit' is also suspect. Are you still seeing that, or has it gone away?

The RPM sensor on the compressor rarely if ever goes bad. I don't think the ECM will let you bypass or disconnect it without introducing some other problem.

I recall that you mentioned changing the pressure switch. It could be that you got a bad one. (Remember, "new" means "Never Ever Worked" )

Take a close look at the connector and whatever wiring is visible. Perhaps something was damaged when the replacement engine went in.

Unfortunately, I have neither a Field Service Manual nor Electrical Diagram for your car. It might be worth subscribing short-term to AllData or Mitchell so that you'll have all of the factory repair information and techniques in hand as you continue to troubleshoot.

Lexus systems are exceedingly complex—IMHO, needlessly complex. You might have to take it to a Lexus specialist to lay actual hands on it and to get a solution.