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).


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

> 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
> 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.

› See More: UPDATE: A/C Pressure Sensor Simulate, 94 Chev. Lumina Sedan