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ThunderRiver

A/c Singal Blinking?

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On my 1994 LS400, the A/C signal light sometimes blinks while I was driving. Is that normal? I guess the sensor is confused about whether turning on heater or A/C, so the light is on and off.

The outside temperature is aruond 30's. If I manually press the A/C button, the A/C light would go off, which means heater would come on until next time I drive again. Whenever I turn on the engine, the A/C is on by default... kind weird at such cold temperature eh?

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I know that in my 98 when the A/C light starts blinking there is a problem with the compressor. Not sure if that extends to you. When my climate control is in auto the A/C comes on at start up. If the outside temp is below 37 the A/C will auto shut off. If the temp is higher then the A/C stays on.

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Usually a blinking A/C light means that your a/c compressor is locking up, which is a bad news. With the hood up, listen to the noise coming from the compressor when it is turned on. If it sounds like a grinding noise, turn it off and don't turn it on again because when the compressor is making a grinding noise, it's pumping metallic filings into your a/c gas system and the more it runs, the bigger the mess you will have getting it cleaned out. You can run an a/c diagnostics check by depressing the a/c AUTO and REC switches simultaneously and then turn the ignition switch to ON while holding the switches depressed. All the lights should blink on and off 4 times and then it will put a code, if any are set, on the a/c display. Good luck.

Curt

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Ecu compares compressor rotaion rate, assuming clutch is enabled, with engine ignition rate, a significant difference will cause the indicator to blink, and I think, the clutch disabled until the next start or A/C off/on cycle. Running through a puddle of water and getting the drive belt wet can cause this and appear intermittent.

Below 37F the A/C compressor will not run regardless of the indication. If you have turned it on manually, or do so after it auto turns off at 37F, the indicator will be on but the compressor will still not run until the OAT rises.

Can't find a way to delete, sorry...

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Ecu compares compressor rotaion rate, assuming clutch is enabled, with engine ignition rate, a significant difference will cause the indicator to blink, and I think, the clutch disabled until the next start or A/C off/on cycle. Running through a puddle of water and getting the drive belt wet can cause this and appear intermittent.

Below 37F the A/C compressor will not run regardless of the indication. If you have turned it on manually, or do so after it auto turns off at 37F, the indicator will be on but the compressor will still not run until the OAT rises.

In the wintertime I switch a 2800 ohm resistor into series with the OAT sensor so the A/C doesn't run if the OAT is below 55F. Prevents most instances of sudden windshield fogover about 5 miles down the road on cold mornings, AND saves fuel.

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The compressor has its own pressure switch it doesn;t loo at rpm's

Once there is sufficent heat under the hood you should have no problem with cold outside to need a resistorto bypass it.

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Clarification...

A blinking A/C indication usually indicates that the ECU has sensed a difference, maybe transient, in engine RPM, ignition rate, and compressor rotation rate.

Below ~55F the A/C is not needed for cooling, but continues operation (primarily to keep windows and windshield from fogging over) based on refrigerant pressure, (lack of) down to about 35F OAT based on the input from the OAT sensor.

Since the A/C is not reliable for this purpose as the OAT declines lower and lower, all it does is result in the incidents of sudden windshield forgging on an early moring drive or anytime then A/C is shutdown for any reason, leaving defrost/defog/demist mode, for instance.

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So I guess I don't have to worry much about it?

I do notice that the car would be making scary noise when the blinking A/C light persists for a long period of time.. like for 30 min to an hour.

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the bblinking ac light usually means that there is an error in AC system and you have to get the error code out in order to understand wha is wrong with it. i just dont remember which 2 buttons u have to hold while turning ignition on to get the error code out. once you get it ouy you will know what is sexactly wrong with your Ac system withouy gusessing.

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the 'Rec' is NOT a switch--it is the rocker on the right of the 'temp' rocker.

turn the ign switch while pressing the 'auto' and bottom of the rocker above[will show the air making a 'u' turn on the rocker.

Advise code #.

post-4-1073870396.jpg

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