A Completely NEW air conditioning problem :)

[Crowz]

Ok the 2001 I recently bought has a unique ac problem.

The air conditioning works perfectly when you first crank the car up and works flawless for awhile. Then the car turns the compressor off and wont turn the compressor back on for 5 or 10 minutes. The it will cool fine for 5 to 10 minutes. Then it turns the compressor off again.

Rinse and repeat.

I have verified the low and high side pressure with the gauge set I have.

Even know the actual temperature of the Freon a the high and low side (cool digital gauges )

No fault codes.

Also I watched all the live data from the computer and all the numbers look great. Even the pressure readings show fine according to the computer.

So if the car is blissfully so damn happy why does it keep turning off the compressor ?!?!???

The scan tool clearly shows the car is commanding the compressor off but looking at the data there is no reason for it do that.

Suggestions?

[Russianblue]

aux fan is working properly? mine fooled me when I had this issue. it was still running but I couldn’t tell if it was working to spec. once I replaced it all issues went away.

[Crowz]

As much trouble as the aux fan is to change if it is bad Im not changing it.

I'll do my own compressor control if I have to.

Its not setting a code for the fan. There isn't much else to do to test it.

[upallnight]

Originally Posted by Crowz

As much trouble as the aux fan is to change if it is bad Im not changing it.

I'll do my own compressor control if I have to.

Its not setting a code for the fan. There isn't much else to do to test it.

Aux fan code is set in the DME module.

[andrewwynn]

The most common reasons for similar threads end up being faulty low side sensors or wiring (my case a faulty connector), the aux fan situation or a problem with the variable compressor.

Since it's coming on but being commanded off: can you read the low pressure value and what is the Ω reading across the low pressure sensor

The other sensor that disables the system outright without any error is the temp sensor I think on the evaporator. The system is designed to inhibit operation when below some ambient temperature (so could be the reading of the ambient temperature also).

Make sure aux fan runs (command on with scan tools, or I think you can unplug a sensor wire I forget which but somebody here will chime in. Also when you first then key on I think the fan should turn like 1/3 of a turn).

[Crowz]

Originally Posted by andrewwynn

The most common reasons for similar threads end up being faulty low side sensors or wiring (my case a faulty connector), the aux fan situation or a problem with the variable compressor.

Since it's coming on but being commanded off: can you read the low pressure value and what is the Ω reading across the low pressure sensor

The other sensor that disables the system outright without any error is the temp sensor I think on the evaporator. The system is designed to inhibit operation when below some ambient temperature (so could be the reading of the ambient temperature also).

Make sure aux fan runs (command on with scan tools, or I think you can unplug a sensor wire I forget which but somebody here will chime in. Also when you first then key on I think the fan should turn like 1/3 of a turn).

All of the sensor readings are within spec. The high pressure sensor is the only one it reads as a value and it followed the pressure readings on the gauges fine.

The low pressure one isn't shown in the data stream. I could mess with it and see what happens but I have never had one fritz out and go back to working that regularly before so I doubt its bad.

I wont be able to mess with it again till later in the week because of the weather. But if I don't run across a solution I will fix up a manual override for when its being annoying

Oh and the temp readings on the evap were reading right too and it made it down to 42 degrees at the lowest point.

[andrewwynn]

My low sensor was intermittent because it wouldn't latch. Yours seems to be time/temp related. You need to measure the voltage across the low sensor while it's running then shuts off. Also the temp sensor whichever the AC system uses to defeat itself


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[upallnight]

Originally Posted by andrewwynn

The most common reasons for similar threads end up being faulty low side sensors or wiring (my case a faulty connector), the aux fan situation or a problem with the variable compressor.

Since it's coming on but being commanded off: can you read the low pressure value and what is the Ω reading across the low pressure sensor

The other sensor that disables the system outright without any error is the temp sensor I think on the evaporator. The system is designed to inhibit operation when below some ambient temperature (so could be the reading of the ambient temperature also).

Make sure aux fan runs (command on with scan tools, or I think you can unplug a sensor wire I forget which but somebody here will chime in. Also when you first then key on I think the fan should turn like 1/3 of a turn).

Fan should spin up and shut down. Once the fan has shut down if you remember your electrical studies a dc motor becomes a generator. The voltage is seen by the DME and this little voltage tells the DME that the fan is OK.

[Crowz]

Well a working fan isn't required for the a/c to work. My wifes fan died about 3 months ago via went wide open and wouldn't cut off. She unplugged the fan to get home which of course knocked out her a/c. I removed the motor from the previous fan which died via not running at all and plugged it into the harness and she has a/c. As long as the fan is plugged in the a/c will work fine even if the fan motor is toast or not spinning. At least it is that way on the wifes x5.

So that's why Im not really eyeballing the fan since there isn't a code for a bad fan and the a/c works for a loooong time before it stops for a bit.

I'll keep messing with it after the rains go thru here.

[upallnight]

Originally Posted by Crowz

Well a working fan isn't required for the a/c to work. My wifes fan died about 3 months ago via went wide open and wouldn't cut off. She unplugged the fan to get home which of course knocked out her a/c. I removed the motor from the previous fan which died via not running at all and plugged it into the harness and she has a/c. As long as the fan is plugged in the a/c will work fine even if the fan motor is toast or not spinning. At least it is that way on the wifes x5.

So that's why Im not really eyeballing the fan since there isn't a code for a bad fan and the a/c works for a loooong time before it stops for a bit.

I'll keep messing with it after the rains go thru here.

So doesn't your statement above prove that you need a working fan for the compressor to engage? A fan that spin is considered a working fan by the DME. Unplugging the fan tells the DME that the fan is not generating a voltage signal back to it so it thinks the fan is broken, so it doesn't command the compressor to engage.