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HELP! A/C Problem, need help identifying issue, turns on then turns off

daurigon on Mon September 12, 2011 3:33 PM User is offline

Year: 1985
Make: Toyota
Model: Levin (Corolla GT-S)
Engine Size: 1600
Refrigerant Type: R12

The A/C kicks on for a few seconds, and then not work, A/C light flashes, so I don't know if its a problem with the climate control amplifier or something i don't know about. (Also, this is a JDM RHD Toyota Corolla Levin so I dont know if the a/c lines, compressor, things like that are in a different area than on the corolla gts for USDM)

more info: A/C is charged, when it does work, the pressure is good and the fans turn on

Is this maybe a bad sensor, or bad compressor? are there any relays or any fuses anything like that that controls the a/c? let me know (and where would this be located) any thoughts on this? thanks everyone!

UPDATE: This is not a A/C recharging issue as I was driving 70, and the A/C started to work and blow ice cold, but maybe 20-40 minutes of driving, the A/C Burton started to flash and stopped working. This happens several times, not just a one time thing. I don't know if it has something to do with how fast I am driving, I don't know....

GM Tech on Mon September 12, 2011 6:59 PM User is offline

Toyotas use rpm sensors, if rpm of pump is no same as engine (prorated for ratio) then a/c is shut down and a/c lite is your clutch slipping at high speed?

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Mon September 12, 2011 7:45 PM User is offline

Like GM Tech said, the blinking light is because the A/C amplifier is not happy with the compressor rpm. It then locks out the compressor until you release and press the button again.

Possible causes:
Compressor failed to rotate at all (seized compressor, clutch gap too wide, bad relay or fuse, broken belt) -- apparently not your case.
Clutch or belt slipping -- This is the situation the system is intended to detect.
Faulty A/C amplifier -- may be just bad connection on the circuit board, do a "solder around"
Faulty compressor rpm sensor or wiring.

daurigon on Mon September 12, 2011 11:42 PM User is offline

Originally posted by: GM Tech
Toyotas use rpm sensors, if rpm of pump is no same as engine (prorated for ratio) then a/c is shut down and a/c lite is your clutch slipping at high speed?

Compressor clutch or the actual clutch of the car? sorry, i do not know anything at all about fixing cars. should i attempt to fix this myself, or should i just take it to a A/C repair shop. does anyone know of any good ones in austin, tx?

because my car is a RHD Japanese car, do you think it will be an issue? just wondering, thanks!

Cussboy on Tue September 13, 2011 2:46 PM User is offline

He means the AC electric clutch on the compressor.

daurigon on Wed September 14, 2011 2:56 PM User is offline

Where is the A/C amplifier located? in the manuals, it says it should be 8 pin, but mine is 12, anything on that?

daurigon on Sat September 17, 2011 9:15 AM User is offline

Hello all!

Yes, I do know now where the A/C amplifier is, thank you for that on this and the other forums.

My next question is regarding an RPM/Speed sensor located on/in/under the compressor. Am I correct in this information and if not, where is this located and let me know how I can find the part to replace it. Thank you!

Pictures would help very much. Thanks!

mk378 on Sat September 17, 2011 10:36 AM User is offline

The speed sensor is going to be screwed into the compressor body, but it is not commonly the problem. First I'd take the A/C amplifier out of the car and open it up, inspect the circuit board for broken solder connections and leaky capacitors (evidence of liquid leaking out of an electrolytic capacitor).

daurigon on Sat September 17, 2011 11:37 AM User is offline

okay, i will do that first.

I ask about the speed sensor because the A/C amplfiier was swapped out with another corollas amplifier and it still did not fix the problem.

you guys dont think it could be something as small as the switch located behind the a/c button when you remove the faceplate do you?

daurigon on Sun September 18, 2011 5:00 PM User is offline

Here is some more info I think it may be:

Also, yes, the electric clutch is not engaging, or it does, but then shuts off and a/c stops working

Well, it WORKS, and then it DOESN'T WORK, so that means an intermittent problem or condition, as opposed to something flat out broken.

When AC works, the freon is being compressed and then flowing and expanding again, all in a closed loop cycle. For that cycle to be interrupted I think there' sonly tow things that can happen.

First, the compressor may be kicking out and not compressing the freon. that could be a bad compressor clutch (separate part, hard to obtain a replacement) or the wiring or pressure switch or speed sensor switch, any part of that could interrupt power to the compressor clutch and then the compressor would stop turning and the AC stop. AND the AC switch should blink to indicate a speed error or someother problems--no one seems to have a full ist of what can make it blink except "bad stuff".

So that's one shop check to make, run the car and AC, and when it stops blowing cold & starts blinking, quickly look under the hood to see if the compressor clutch has stopped. If it has, rig up a manual power cord to it, see if feeding it 12V+ will engage the clutch and make the system run again.

The doesn't mean bypassing all the safeties is a good fix--there may be a reason they are cutting off the power! But it will tell you if the problem is the compressor cutting out, as opposed to:

The other problem can be a blockage. The system can form ice, typically at the evaporator orifice(?) if there is moisture in the system, or too much gas. If the system was repaired recently and someone did not change the receiver/drier, that could be all it takes to freeze it up. The solution is purge the system, replace the r/d, and refill the system again.

I'd guess a remote third is that the ac amplifier (that's just got to be a lousy translation!) is keeping the system running too cold, but AFAIK these systems are so underpowered there's no way to freeze it up by running it for hours and hours on end, unless there's something else wrong like moisture in the system.

mk378 on Sun September 18, 2011 6:13 PM User is offline

The blinking light is definitely a rpm mismatch or perceived rpm mismatch. The A/C amplifier really isn't wired to check for anything else. It's not like what Cadillac did later with a computer that checks everything about pressure and temperature. If you have a blockage or freeze up the compressor will keep spinning, the amplifier does not care. If the condenser fans don't work you may get an overpressure trip, which might cause a blinking light (I would have to look at the diagram). That cannot not happen at highway speed though. Do your condenser fans start when the compressor starts?

Edited: Sun September 18, 2011 at 6:14 PM by mk378

daurigon on Sun September 18, 2011 6:17 PM User is offline

I believe so, but the second the a/c light blinks, i lose a/c, the compressor clutch stops working. fans stop,

its weird, when i start at a cold start, my rpm is at 2k, and as the car warms up and slowly comes down to 1k, the second it hits that 1k, it shuts off.

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