A/C compressor only kickin in every now and then

[2005chevimpala]

Having a problem with my a/c kickin in and out,if i pull the 2 fuses out in the fuse box under the hood and put them back in sometimes a/c will kick in and work,when it is working and i shut the car off and restart her and put the a/c button on she won't kick in,i changed the 2 fuses under the hood in each fuse box to 2 new ones and now she won't kick in at all,i unpluged the main wire on the compresser and pluged it back in and sounds like there is power going to it cause it makes adifferent sound when you unplug it and plug it back in but won't kick in,now the only thing i can see is where she has an antifeeze leak that i think id coming out of the weep hole in the water pump that there is a lot on antifrezz on the plug on the compresor and along the wires in the harness,i had it working but when i shut the car off and started her again the a/c would'nt kick in,i also put a small bottle of bardal stop leak in the rad,the one that says stops leaks and lubricates the water pum seal to see if the leak slows down or goes away to see if that is where my leak is coming from,anyway i'm still curious as to why my a/c compressor only works once and a whil,anyone help please,i never had a problem with the a/c or any leaks until the garage put that new cam and lifter in under warranty and still as of last week they did a pressure test on her 7-8 times and keep telling me they can't find it although the water/antifreeze is on the right pass side leakin onto the front of the rad and plastic fan shroud,just came in from taking out and putting the fuses back in and unplugging the main plug on the compressor again and can't get it to come on at all now,i can spin the cluch fan freely by hand

[wafrederick]

The relay might be stuck,carefully tap on it with small hammer or with a handle of a screwdriver.

[2005chevimpala]

Originally Posted by wafrederick

The relay might be stuck,carefully tap on it with small hammer or with a handle of a screwdriver.

i switched the relay under the hood with another with the same number,i was wondering in the owners it says that the a/c won't kick in if the temp outside is lower then 4 degrees,where i live in canada right now outside it is -19,is that why it's not kickin in because its cold out,if so it does'nt explain why an hour ago with it still being -19 out i had it working but now i can't get it to work at all.

[j cAT]

Originally Posted by 2005chevimpala

i switched the relay under the hood with another with the same number,i was wondering in the owners it says that the a/c won't kick in if the temp outside is lower then 4 degrees,where i live in canada right now outside it is -19,is that why it's not kickin in because its cold out,if so it does'nt explain why an hour ago with it still being -19 out i had it working but now i can't get it to work at all.

you cannot have the a/c compressor engaging when the temp is below 40deg F....this is because if it does run the compressor will pump liquid refrigerant and this WILL destroy the compressor...there is a switch that controls this....

after the engine heats up the compressor may run for a short amount of time but then shut down because of the low temps...

[2005chevimpala]

Originally Posted by j cAT

you cannot have the a/c compressor engaging when the temp is below 40deg F....this is because if it does run the compressor will pump liquid refrigerant and this WILL destroy the compressor...there is a switch that controls this....

after the engine heats up the compressor may run for a short amount of time but then shut down because of the low temps...

ok then thanks for the info,i will try to see if it kicks in when the temp rises and warms up abit, in the meantime my engine was running for over an hour and the temp hand was up half way but she still did'nt kick in at all

[HeMi101]

40 degrees is below the Latent heat of Vaporization (Boiling point) for the pressure of the high side of the system so it won't become a gas. If there's liquid refrigerant on the high side, it will be sucked into the compressor, and well Liquids can't be compressed like a gas so it can severely damage the compressor. It's called Slugging.

[2005chevimpala]

Originally Posted by j cAT

you cannot have the a/c compressor engaging when the temp is below 40deg F....this is because if it does run the compressor will pump liquid refrigerant and this WILL destroy the compressor...there is a switch that controls this....

after the engine heats up the compressor may run for a short amount of time but then shut down because of the low temps...

yes you are right,i just went to see if it would click in and come on and it did,it's exactly 4 degrees out there now and it seemed to be coming off and on like it should,thanks for the info,where is this switch your talking about that controls the compressor temp to make it not work in cold temp's

[brcidd]

It is not a switch- it is a three wire pressure transducer- so don't try to jumper it- if you have climate control (digitsl temp readout to adjust inside temp) then the car will not allow a/c operation below the 40 deg limit. Otherwise system pressure must be up around 47 psi (as read by the transducer) to engage the compressor.

[2005chevimpala]

Originally Posted by brcidd

It is not a switch- it is a three wire pressure transducer- so don't try to jumper it- if you have climate control (digitsl temp readout to adjust inside temp) then the car will not allow a/c operation below the 40 deg limit. Otherwise system pressure must be up around 47 psi (as read by the transducer) to engage the compressor.

ok thanks for the info,this is 3 hours later and its still 4 degrees out so when i went out to the store for curiosity i tried it again but the heater switch was in defrost mode so i did''t here the compressor kick in until i put the heat switch on the vent/floor or just vent position,then she kicked in,i thought a/c would kick in on defrost too but it does'nt

[j cAT]

[quote=brcidd]It is not a switch- it is a three wire pressure transducer- [quote]

In my diagrams it is refered to as the A/C LOW PRESSURE CYCLING SWITCH.. it has only 2 wires going to it...

when properly charged and the temp of the refrigerant drops to approx 40deg this switch opens the feed to the A/C COMPRESSOR CLUTCH..

So I am very interested in when GM started using expensive pressure transducers in their a/c systems as I have no data on that...

[2005chevimpala]

[quote=j cAT][quote=brcidd]It is not a switch- it is a three wire pressure transducer-

In my diagrams it is refered to as the A/C LOW PRESSURE CYCLING SWITCH.. it has only 2 wires going to it...

when properly charged and the temp of the refrigerant drops to approx 40deg this switch opens the feed to the A/C COMPRESSOR CLUTCH..

So I am very interested in when GM started using expensive pressure transducers in their a/c systems as I have no data on that...

thanks for the info but i don't see where the wires are for this just for my curiosity

[brcidd]

GM went to pressure transducers primarily with the variable stroke compressors in the mid 90's. The transducers can read continuous pressure to be able to turn on the fans, turn off the compressor if pressure is too low or too high. Almost all GM passenger cars use them. A 2005 Impala definitely has one since it has the CVC a/c variable stroke compressor on it (it does not cycle by design- therefore, no cycling switch)