CHKEE750CF

Ok...I am a retired (not old) Porsche technician. I went ahead and purchased the factory manual for my 1998 Mustang GT 4.6 2V. I have an issue with the A/C compressor not coming on. Here is what I have done so far using the Pinpoint guide in the factory service manual:

I have checked for refrigerant - checks OK

Checked B+ at A/C cycling switch connector/jumpered connections - checks ok/no change

Checked B+ at Pressure cut off switch connector - checks ok

Checked resistance on connections on the Pressure switch that are for the over pressure cutoff(normally closed) for resistance (5 ohms or less) - checks ok @ .2 ohms

Checked resistance on connections on the Pressure switch that are for the fan speed increase (normally open) - checked ok, open circuit

Removed CCM and checked for B+ on the DG/O wire - checked OK

Removed connector on PCM and checked for B+ on DG/O wire - checked ok

Checked to see if compressor clutch will engage with the PCM disconnected - It does

Now the manual says to drag out the Powertrain/Emissions Control manual. HELM is out of them. I reconnect the PCM and low and behold the A/C works just fine until the next morning.

I start up the car and notice that the A?C wont come on. While the engine is cold and the A/C is off, the fan is operating...really weird. I am thinking that there is a temperature sensor that is indicating an overheating condition and cutting the A/C off and operating the fan. Does anyone out there know the rest of the diagnostics procedure?

Any help is greatly appreciated,

CHKEE750CF

CHKEE750CF

Well, I figured it out and here is what it is. THe CCM was bad. At 107k I was suspecting this anyway but it is a $130 part and I dont like playing the guessing game with expensive parts. I did ask the guy at the parts counter if they replaced more PCM's than CCM's and it was a resounding answer on the CCM. So I am now nice and cool...now on to the intake project.