95 Firebird / Camaro A/C problem

[96CamaroSS]

Ok maybe someone can shed some light on this problem. My wife's car 95 Firebird formula a/c quit a few days ago. So far I've checked the charge and changed the high side pressure sensor, but the clutch will not engage. If I bypass the relay the clutch comes on and the a/c works. I've swapped out the relay with another one from my car that works and still no luck. I've read through my 93 GM camaro service manual and it shows a low side pressure sensor next to the high side one. I've been all over under the hood of this car and there is no sensor that I see. So the next question is did gm change the a/c system between 93 and 95 and move the sensor? Where in the world is the low side sensor?

[j cAT]

Originally Posted by 96CamaroSS

Ok maybe someone can shed some light on this problem. My wife's car 95 Firebird formula a/c quit a few days ago. So far I've checked the charge and changed the high side pressure sensor, but the clutch will not engage. If I bypass the relay the clutch comes on and the a/c works. I've swapped out the relay with another one from my car that works and still no luck. I've read through my 93 GM camaro service manual and it shows a low side pressure sensor next to the high side one. I've been all over under the hood of this car and there is no sensor that I see. So the next question is did gm change the a/c system between 93 and 95 and move the sensor? Where in the world is the low side sensor?

not sure on this model but the low side pressure switch with a pressure on the low side at 5psi or more should be closed.. the switch screws into the piping or the receiver dryer tank..with the vehicle engine off remove the connector to this switch then using a ohmmeter measure resistance it should be zero ohms / a dead short...if open this switch is bad this switch works all the time... the high pressure switch does not and therefore normally is not an issue...

make sure all fuses are good..

after all that then check for voltages at the compressor clutch..could be relays and other wiring issues..including an open clutch coil....

[danielsatur]

Check the AC relays too!
The low pressure side is larger for vacuum.

[96CamaroSS]

Well after all the headache the a/c started working on its own again and has not quit yet. I never did find a low pressure switch in the a/c system, because I don't think it exists. On these cars the ecu gives the signal to turn the compressor on and off.

[j cAT]

Originally Posted by 96CamaroSS

Well after all the headache the a/c started working on its own again and has not quit yet. I never did find a low pressure switch in the a/c system, because I don't think it exists. On these cars the ecu gives the signal to turn the compressor on and off.

the ac system must have low and high pressure switches. this is a safety device. the pcm needs input on ac system operating parameters it must have input to control anything on your vehicle.no input no control !

this may have started working again because of wiring issues or the switch just started working again..these switches are known to be erratic in failing.. I suspect this will return..I'm sure if you really want to know whats up with this,,,, a repair manual you buy , or a library has to review the location of these switches...

normally the low switch fails because it works all the time...high pressure switch would be used if overcharged or a condener unit blocked with a very hot air temp...this is not that often if ever....

[j cAT]

Originally Posted by 96CamaroSS

Well after all the headache the a/c started working on its own again and has not quit yet. I never did find a low pressure switch in the a/c system, because I don't think it exists. On these cars the ecu gives the signal to turn the compressor on and off.

I found info on your issue. the low pressure control with your vehicle is not a mechanical switch but a solid state switch [more money greater failure] with this it is still located in the line going to the evap unit mounted on the passenger side of the vehicle in the engine compartment .


the diagram clearly shows high pressure and low pressure measuring devices which input into the ac control unit.. the relay then allows power to the ac clutch ...