Hi,

Sometimes it is better to do it yourself. I am going to
get an A/C pressure gauge and refill kit. Apparently, my cousin
made an error or his gauge is faulty?

I used a 5K pot to simulate the pressure sensor. From the
ECM are three wires, +5, Gnd, and Pressure sense. With the
engine running and A/C at MAX, I adjusted the pot (preset at
around 2V (logic low/low pressure)) to above +3V (logic high)
and the A/C clutch engaged. After running the A/C at max,
the air temp wasn't getting cold so it looks like the pressure
sensor was working. I will "recharge" the system and see
how long it last. It can very well be that my original conclusion
was correct (leak at compressor).

Brad

On Tue, 01 Aug 2006 14:56:35 GMT, bpetria@verizon.net (Brad) wrote:

>Hi,
>
> My Mom's 94 Chev Lumina (V6 3.1 liter) A/C stopped working. In a process
>of elimination (see "Test Results" below), I have eliminated some things
>already. Note: The A/C compressor clutch doesn't engage when A/C is turned
>on. According to Haynes service manual, this car (3.1 liter engine) doesn't
>have pressure switches (I couldn't find any).
>
> I removed the connector (3 wires) from the A/C pressure sensor.
>This sensor symbol in a Haynes service manual looks like a potentiometer
>with ground on one end, +5V on the other and a wiper arm (pressure).
>The wires run to the ECM. It is extremely difficult to measure the sensor
>resistance so I can use a regular "pot" of the same resistance to simulate
>the pressure sensor.
>
> A Google search did not reveal the information I need.
>
> Do you know any tricks to eliminate the pressure sensor?
>
> Thanks in advance, Brad
>
> TESTS RESULTS:
>
> My cousin brought his A/C pressure gauge and said the pressure was normal
>(checked on low side) with engine running A/C on "MAX".
>
> I checked the A/C relay in my service shop and checked the "HVAC" fuse
>(only fuse for AC). I disconnected the connector from the compressor clutch
>and checked for voltage with engine running and A/C on "MAX". No voltage.
>
>