1992 LS400 - Air Conditioner problem
10-07-09, 06:06 AM
#16
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AMSKEPTIC: Thank you!
Amskeptic: Thank you, thank you. 
Your step-by-step post was EXACTLY the guidance I was looking for. Here's what happened:
I started the engine and turned on the a/c. I then looked down into the engine bay, only to realize that I had no idea what an a/c compressor looked like, nor did I have any idea which of the myriad pulleys was the pulley in question.
In any event, operating on the assumption that the compressor wasn't engaging at all, I followed your instruction and removed the big plastic cover over the fuses and relays. I found the round relay closest to the left fender. (By the way, the diagram on my inside cover does not identify it as an a/c relay, but as a "M/G CLT" or something to that effect (sorry, I put the cover back on before writing down the label). Fortunately, it is the only round relay in the compartment.)
I then removed the round relay and saw two copper spades and two lighter (but not quite silver) spades. I bridged the copper spade terminals inside the fuse box with a piece of wire, and presto, I did in fact hear the sound of the compressor engaging, along with a change in the engine rpm! And yes, I did get a little spark action, but thanks to your sage advice, I knew it was no big deal, just like you said.
Before I go messing around with recharging the refrigerant, would it be prudent for me to first ascertain that the relay is good, and that it hasn't failed? I wonder about this only because my a/c system was converted to R-134 just over a year ago by a Lexus dealership, and so I'm assuming that plumbing/refrigerant-wise, that the a/c system should be up to snuff. I'd hate to mess around with the system if the problem can be solved with a simple replacement of the relay.
Although I am a total car neophyte, I have fooled around with an ammeter or two in my life. Would it be as simple as testing the "control" side of the relay socket for some voltage drop while the a/c switch is on?
Would it be too much of an imposition for me to ask you, Amskeptic, to indulge me for a bit and post more detailed instructions on how to proceed from here? I would be indebted.
Amskeptic, thanks again. Your previous post was an ENORMOUS help and probably saved me several hundred dollars. I look forward to any more information you can/are willing to share.
Your step-by-step post was EXACTLY the guidance I was looking for. Here's what happened:I started the engine and turned on the a/c. I then looked down into the engine bay, only to realize that I had no idea what an a/c compressor looked like, nor did I have any idea which of the myriad pulleys was the pulley in question.
In any event, operating on the assumption that the compressor wasn't engaging at all, I followed your instruction and removed the big plastic cover over the fuses and relays. I found the round relay closest to the left fender. (By the way, the diagram on my inside cover does not identify it as an a/c relay, but as a "M/G CLT" or something to that effect (sorry, I put the cover back on before writing down the label). Fortunately, it is the only round relay in the compartment.)
I then removed the round relay and saw two copper spades and two lighter (but not quite silver) spades. I bridged the copper spade terminals inside the fuse box with a piece of wire, and presto, I did in fact hear the sound of the compressor engaging, along with a change in the engine rpm! And yes, I did get a little spark action, but thanks to your sage advice, I knew it was no big deal, just like you said.
Before I go messing around with recharging the refrigerant, would it be prudent for me to first ascertain that the relay is good, and that it hasn't failed? I wonder about this only because my a/c system was converted to R-134 just over a year ago by a Lexus dealership, and so I'm assuming that plumbing/refrigerant-wise, that the a/c system should be up to snuff. I'd hate to mess around with the system if the problem can be solved with a simple replacement of the relay.
Although I am a total car neophyte, I have fooled around with an ammeter or two in my life. Would it be as simple as testing the "control" side of the relay socket for some voltage drop while the a/c switch is on?
Would it be too much of an imposition for me to ask you, Amskeptic, to indulge me for a bit and post more detailed instructions on how to proceed from here? I would be indebted.
Amskeptic, thanks again. Your previous post was an ENORMOUS help and probably saved me several hundred dollars. I look forward to any more information you can/are willing to share.
Last edited by somnoboy; 10-07-09 at 10:44 AM.
10-09-09, 06:35 PM
#17
The correct next step is to throw a gauge on the low side of the system to see what your static pressure is, then watch to see if the gauge plummets when you fire up the compressor.
Local auto parts stores have R134 with gauges on the end of the installation hose. You can slap the gauge/hose right on the low side tap without a can attached to it, just don't squeeze the trigger. You will see blue/green/yellow/red bands on the gauge. With the compressor off, the gauge should read yellow or blue. If it is in the green zone, it has most likely lost its charge or there is a restriction. It will of course go down from the static reading as the compressor asks for refrigerant gas from the low side, but if it sucks down to zero, you are definitely too low on refrigerant or you have a nasty restriction. Do not run the compressor with your hot wire for any longer than is necessary if this is the case.
My guess is that you may have either a leak or a restriction. Conversions from R12 to R134 have all kinds of risks, not the least of which is that few shops really clean the system out when converting.
Colin
Last edited by Amskeptic; 10-10-09 at 03:47 PM. Reason: added sentence "do not run the compressor . . . ." changed blue/green placements in text
10-14-09, 07:15 AM
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Thanks Amskeptic. I actually need to step away from this for about a week. In the meantime, I saw on one of the other threads you mention a (presumably) Toyota published workbench/workshop/service manual for the '92 LS400. You were noting how complete and thorough it was. Could you possibly tell me how/where to procure a set (preferably new, but used if necessary)?
Thanks.
Thanks.
10-20-09, 06:03 AM
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Confirmed: Relay
Amskeptic: I just confirmed with an ammeter that no electrical power is being sent to the "control" side of the relay socket when the air conditioner is turned on. Thus, I suppose that there really is low refrigerant pressue in my a/c system, thereby causing no signal to be sent to the a/c relay.
I guess you were right, amskeptic. Now I need to get some refrigerant, and I'll check the pressure.
I guess you were right, amskeptic. Now I need to get some refrigerant, and I'll check the pressure.
10-30-09, 02:45 PM
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a/c problems part 2
Hello everyone. I'm new to ClubLexus and am very impressed with the very professional expertise exhibited here.
Anyway, I have a 1992 LS 400 with about 92,000 miles. I am the original owner, and have kept the car garaged since birth. It is in mint condition.
Just about a year ago, the air conditioner stopped making cold air. System was converted to R-134 at a Lexus dealership. Since then, a/c worked fine up until yesterday (I think). Now, fan works fine, but with A/C switch on, no cold air is produced. The air being blown is whatever the ambient air is outside. I noticed that when idle in park, that turning the a/c on or off results in absolutely no change in engine rpm. In other words, it almost seems as if the a/c isn't engaging at all. The a/c light stays on steady when selected (no blinking).
I ran an a/c diagnostic code check, and the only codes that show up are 00 and 21 (I was idling in park in the shade, out of direct sunlight).
Any experts out there have any idea? I am very, very proud of my LS 400, and would greatly appreciate anyone's help.
Thanks in advance.
Anyway, I have a 1992 LS 400 with about 92,000 miles. I am the original owner, and have kept the car garaged since birth. It is in mint condition.
Just about a year ago, the air conditioner stopped making cold air. System was converted to R-134 at a Lexus dealership. Since then, a/c worked fine up until yesterday (I think). Now, fan works fine, but with A/C switch on, no cold air is produced. The air being blown is whatever the ambient air is outside. I noticed that when idle in park, that turning the a/c on or off results in absolutely no change in engine rpm. In other words, it almost seems as if the a/c isn't engaging at all. The a/c light stays on steady when selected (no blinking).
I ran an a/c diagnostic code check, and the only codes that show up are 00 and 21 (I was idling in park in the shade, out of direct sunlight).
Any experts out there have any idea? I am very, very proud of my LS 400, and would greatly appreciate anyone's help.
Thanks in advance.
I had the compressor replaced with a new denso c/w clutch and re-filled with r12. Why r 12 do you ask? R12 has larger molecules than r134a.
Because all the seals and gaskets are built for r12, there is a possibility that the older seals and gaskets MIGHT cause a slow loss of r134a and a loss of efficiency of 4 to 8 degrees in coolness. For me it was a no brainer for the r12 and if I have any further problems, It's only 25 minutes drive to my favourite a/c repair shop.
Good luck on your dillema.
11-04-09, 02:49 PM
#21
Anyone know if the How to Che Air Conditioning Diagnostic Codes on a 2000 LS400? I recently purchased a 2000 LS400, as is, got home from a 4+hour drive and it worked all the way. Now a few days later it only blows hot air. I was told they replaced the compressor.
05-13-11, 10:52 AM
#23
Please note that it is all too easy for us keyboard cowboys to throw out our favorite ideas, many of which are only brought up because "it happened to me last week".
You have to get out to your car and start thinking like an engineer.
Start engine. Turn on the A/C. Go look down at the compressor. The pulley will be turning, but we are interested in the center part that sticks out closer to the front of the car. Is it turning? Yes means you have an internal issue to the A/C plumbing/compressor if there is no cold air.
If it is not turning, be brave. Remove the big plastic cover over the fuses and relays. There is a round A/C relay closest to the left fender and it is identified on the diagram inside the cover. Remove it. You will see (if it is factory) two copper spades and two silver spades. You want to bridge the copper spade terminals inside the fuse box with a little piece of wire just to check for the sound of the compressor engaging. You might get a little spark action, no big deal- you at least know you have voltage coming through the load side of the relay, just cram the wire in the terminal slots briefly. This will normally make the idle go up as well.
If this little hot-wire makes the compressor engage, you likely have a low charge of refrigerant. In this case, the relay's control circuit is being told not to engage the relay due to insufficient pressure stopping the electrical circuit to the relay control coil.
If the compressor still does not engage, you have a possible wiring/compressor clutch problem. If you were not a neophyte, I would say check for 12 volts at either of the two terminals on the switch-side of the relay plug. There is a "locked rotor sensor" designed to prevent the clutch from killing itself if the compressor is seized up. This will cause a blink in the little green light at the switch.
Colin
You have to get out to your car and start thinking like an engineer.
Start engine. Turn on the A/C. Go look down at the compressor. The pulley will be turning, but we are interested in the center part that sticks out closer to the front of the car. Is it turning? Yes means you have an internal issue to the A/C plumbing/compressor if there is no cold air.
If it is not turning, be brave. Remove the big plastic cover over the fuses and relays. There is a round A/C relay closest to the left fender and it is identified on the diagram inside the cover. Remove it. You will see (if it is factory) two copper spades and two silver spades. You want to bridge the copper spade terminals inside the fuse box with a little piece of wire just to check for the sound of the compressor engaging. You might get a little spark action, no big deal- you at least know you have voltage coming through the load side of the relay, just cram the wire in the terminal slots briefly. This will normally make the idle go up as well.
If this little hot-wire makes the compressor engage, you likely have a low charge of refrigerant. In this case, the relay's control circuit is being told not to engage the relay due to insufficient pressure stopping the electrical circuit to the relay control coil.
If the compressor still does not engage, you have a possible wiring/compressor clutch problem. If you were not a neophyte, I would say check for 12 volts at either of the two terminals on the switch-side of the relay plug. There is a "locked rotor sensor" designed to prevent the clutch from killing itself if the compressor is seized up. This will cause a blink in the little green light at the switch.
Colin
05-16-11, 05:46 AM
#24
I have been gratified to note that my crazy compressor rebuild on the floor of my brother's garage two years ago... :
.... is still working fine, a little noisy when it is hot outside.
Colin
.... is still working fine, a little noisy when it is hot outside.
Colin
05-08-12, 09:15 AM
#25
Just had my '92 A/C converted to R-134 and it's almost TOO cold. Surely I won't think so come July/August Georgia heat.
11-09-12, 01:25 AM
#26
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Hi all, I have the same problem with my 91 LS400. It doesn't blow out outside temp air, but it blow out heat even if I turn the A/C on. Can some one point me to the right direction on what to check or to do? thank you so much.
11-10-12, 12:42 AM
#27
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It doesn't blow out outside temp air, but it blow out heat even if I turn the A/C on.
11-12-12, 02:29 AM
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How do I fix that? I also diagnose it with code 11 & 21. I've read up to see what it is but have no clue on how to fix that or where it's located. Would someone please help. Thanks so much.
11-13-12, 09:16 PM
#29
The heater control valve on yours is located against firewall on passenger side. It has two hoses running in and out. if you look at it see what position the arm is at start the car and switch between ac and heat and see if the arm moves. If not probably bad. Its super easy to replace on the 91. I did mine because it leaked. Took less than an hour.
Search for that to see photos.
If a damper door in the dash is stuck than that may be big trouble due to nature of getting to it. So hope thats not your issue.
Search for that to see photos.
If a damper door in the dash is stuck than that may be big trouble due to nature of getting to it. So hope thats not your issue.