Curt

I bought a 1990 Lexus LS400 with 214,000 miles and a dead air conditioner. I guessed that there's probably a freon leak somewhere and after I replace that part and switch over to R134a, I should be good to go. I can turn on the AC, and the light comes on, but there is no cold air coming out of the vents.

I bought the R134a conversion kit and a can of dye (all together about $40 at Wal-mart). I then discovered that my car already had the R134 fittings on it. I put in the can of dye, and when about half of it had gone in, the engine died. I re-started the engine and turned the AC back on. The engine bogged down and died again. I re-started the engine, revved it up, and turned on the AC again. This time it bogged down for about 2 seconds, but didn't die. Then the AC light started flashing.

If anyone knows what is wrong I would love to hear your thoughts. I can think of these possibilities:

1. There is a plug in the system. The compressor can't pump the freon past the plug and the AC system senses the problem, then releases the clutch and warns me with the flashing light. So there is probably a freon pressure sensor and/or speed sensor at or after the compressor.

2. The pressure sensor or speed sensor is bad. I don't think this is the case since the engine bogs down when I turn on the A/C if freon is in it.

3. The compressor is seized up. I don't think this is the problem, since I can run the AC system without freon. Only when I add freon do I get the bogged down engine and flashing light.

I tried the AC again a couple of days later, without adding freon, and the AC light comes on and stays on, and the engine doesn't bog down, so I'm pretty sure I do have a freon leak somewhere. I didn't see the red dye anywhere, but I'll look for it some more.

So I think my system has two problems -- a plug and a leak.

I am planning to change my filter/drier/accumulator after I find the leak and before I re-charge the system, so if I'm doubly lucky the leak and the plug will both be there. The car sat for a few months before I bought it, and the AC probably didn't work for many months or years before that, so there could easily be a chunk of rust or God-knows-what in there.

I'm thinking about doing this diagnostic procedure:
Remove the discharge line from the drier (going to the orifice and evaporator). Then start the engine and AC. If the system does not bog down, then the plug is most likely in the orifice. If it does bog down, then the plug is in the filter/drier or earlier. Then I would take the other line off the drier and try again. If the engine doesn't bog down, then the plug was in the drier and I'm home free. If it still bogs down, then it's in the condensor or compressor or one of the lines from the compressor to the condensor or from the condensor to the drier. Does this make sense, or am I an idiot?

Any ideas or suggestions will be greatly appreciated.

Curt

blkstealthpaid4

My light also flashes and it started flashing about a year ago but will reset after I play with it.Now even after playing with it, I still get the same flash.Someone said it is the clutch on the AC compressor.I am about to change the compressor and I hope I am right.

VVT-i

You have 2 problems. One is a big leaks in the system and most likely the Evaporator located behind the glove box.
Second, your compressor and clutch is locking up that why when you turn on the AC, it's almost killed the engine.
These 2 problems are the most comon AC problems on the 1st gen LS with Evaporator+expansion valve leaks, AC compressor and liquid line leaks. From the ages of the car I think it's exceptional.

Curt

Yes, I agree that I must have big leaks in my system. I had a measurable loss in pressure in two days. I haven't found the leaks yet, but they're definitely in there somewhere. But I think my compressor/clutch only locks up when there is freon in the system. Otherwise it spins freely. Are you sure they are bad?

I have a new hypothesis which may agree with you. This hypothesis requires two assumptions:
1. The car has a pressure sensor which keeps the clutch disengaged unless there is freon in the system.
2. My compressor is seized.
If both of these are true, then I thought the compressor was spinning freely when really it was not. That would also explain why the engine bogged down so badly.

Does anyone know if there is such a freon pressure sensor in the 1990 LS400? And does anyone know if the clutch will not engage unless there is adequate freon pressure? Thanks,
Curt

lextek

There is a low pressure sensor that prevents the clutch from engaging when the freon level is low so the compressor won't burn up. If the light is flashing you need to replace the compressor and clutch. It would also be a good idea to replace the suction and discharge lines since you will have "new" pressures with the new compressor. Also, replace the drier so the job is done right.

Good Luck.

Curt

Thanks for your input. I always thought this car was too smart for it's britches. But in this case, it sounds like a good thing.

I ordered a repair manual on CD, and it should come in a few days. I'd like to see that sensor in an electrical diagram.

If this is all going according to this hypothesis, then doesn't that mean that my compressor is seized and my clutch is working perfectly? The clutch slips until it is supposed to engage, then it grabs so hard it can kill the engine. That sounds like a good clutch to me. What do you think?

I have heard of hoses and seals getting old and leaking, so maybe I should take your suggestion and go ahead and change them, too. Do you know if I have to buy them from the dealer? And I will definitely put in a new drier. I already bought one.

I'll know more when I spend a little more time on the car. Thanks everyone.
Curt

blkstealthpaid4

Thank you Lextek.I suspected the compressor on mine was bad.I found one at a yard for $150 rather than paying $700 for a rebuilt one.I even called this place that have them for 299 and they will not only sell the compressor but also the condensor.They claim the LS is notorious for the compressor siezing after the condensor gets clogged and she said with only the compressor the the system will go out again.She claimed the light flashing was a "catastrophic failure" in the AC system.Hell I am not replacing the condensor and I believe cleaning the system and charging it will work after changing out the bad compressor.

LexLS

I wish this thread started earlier! You can't get much worse than what happened to me...entire A/C system failure. I had the flashing light, a "catastrophic failure in the AC system." The fix, all major parts in my A/C system were replaced and all lines cleaned. I don't think reading this thread would have saved me any money, but it would have been nice to know what the flashing light meant!

Good luck with your system Curt, it's worth fixing because it's cold!

lextek

You guys are thinking too deep into this.....albeit a good thing. First thing when the flashing light appears the rpm sensor on the compressor is seeing something it shouldn't, because it's programmed to see a certain thing at a certain time. This is what I would do. Remove the compressor and clutch, when the compressor is being replaced the manifold or top of the compressor is removed and transfered to the new compressor. Inspect the inside of the old compressor and old lines, if there is gray or black "powder" in these areas then "black death" or "grey or gray death is present" you have problems then and big ones. That doesn't happen too often. Ninety percent of the time a flashing light means a locked up compressor or one on the blitz, a clutch is often put on as a precautionary measure by a dealership to prevent the dreaded comeback....hey it's easier to tell the customer one lump sum then to piece him or her to death. The right fix is a compressor, clutch, and both lines along with the drier on a blinking a/c light. Period.

Good Luck.

ToddLS400

Hold the OFF and RECIRC button at the same time as you turn the ignition to the on position. This will display error code(s) in the top LCD for you.

Curt

I LOVE error codes! Flashing lights mean something, but error codes really mean something. Now if only I had that blasted AC climate control dislplay LCD fixed!

I am working to get some of these LCD displays. I am pretty sure I can do it. I hope to get a sample late this month. If it works, Mikado will be in for some competition!

Curt

persian451

this is a really old thread.. I know..

but I just took my car in to get my AC blinking light checked out.. this is what they quoted me..

Replace A/C Compressor - $140
Recover A/C refigerant - $70
Replace Condensor - $210
Replace Drier - $63
Flush A/C System - $140
Total Labor $623

Condensor - $491.34
A/C Compressor & Drier - $400+shipping <I found>
R-12 Freon - $188.49


Now they told me that my Condensor was leaking.. I find this hard to believe because I've yet to find any clublexus member with a bad 1st Gen LS A/C condensor..

any thoughts?

GRAND_LS 4

iTrader: (2)

I agree, it sounds like a dead compressor if you dont hear it running, why do you have to replace the condensor, and
drier?

Also, a flush for $140? what are they flushing?

persian451

they said that.. when the compressor goes bad.. metal shavings supposedly get in the lines.. and all the lines need to be flushed.. some stupid thing.. i dont beleive it..

I dont have a problem with the reciever/drier, since its common to change that with the compressor. But I'm still heated about changing a condensor along with flushing the system.. idont know who to trust anymore these days..