When jumping out the cycle switch on the low line, the compressor does not come on. But while its still jumped, if you ground it out the compressor comes on and blows cold, although the secondary cooling fan doesnt come on. If this is a bad ground, where would you start? could this cause both problems?
thanks

 

If your car has electronic A/C see if the green light is flashing on the dash display. If it is you will need to disconnect the battery to reset or clear the code before the compressor will function correctly.

 

In regard to your comments and reviewing the 94 schematics which should be the same as the 93.

By grounding out that point you are doing what the HVAC programmer does when it operates normally. It does ground that point to enable the A/C clutch relay to close by grounding the low side. So as stated in above post, it may need to me re-set because it does not seem to be functioning now. That would be the first step, then go from there is it does not resolve the problem.

The secondary fan (passenger side) does not come on with the A/C. Only the primary fan. The secondary fan comes on in regard to engine temperature which is 239*. The sensor in the water pump feeds the ECM which then makes the decision to turn the fan on at 239*. So that does not seem to be a problem for you.

 

Programmer grounds nothing - Low Pressure Switch is closed above 50 psi and open below 25 psi. Jumpering the harness is the same as a closed switch.

PCM drives/grounds the Compressor Relay. Signal is from the Controls over serial data lines to the Programmer and then to the PCM.

Low Pressure switch is monitored by the PCM for rapid cycling (open/closed conditions). The open removes ground from the Relay. Rapid cycling is read as a low charge condition. Trouble code, via the CCM link (where it's stored), is sent to the Controls.

PCM monitors the Pressure Sensor Voltage (high pressure line) and looks for it to rise when the Clutch is engaged. If it doesn't, ground is removed from the Relay. If it rises above 400 psi, ground is removed for safety reasons.

Fans are driven based on the Pressure Sensor Signal. Primary around 2 volts or 200 psi - Secondary north of that Pressure. Target is to maintain head pressures that average 200 psi. Depending on outside air temp, one or both fans will be running with the compressor engaged.

Start by disconnecting and reconnecting the battery to clear any codes. If it still won't run and if you don't have a Scanner or Manifold Gage Set, verify that the Low Pressure Switch contacts are closed (use a DVM) and if they are, you might try a new Relay. Otherwise, diagnostics (and it's the only way to verify your fans) is easier with at a scanner as you can then view the Pressure Sensor Signal. Any gas in the system will close the Low Pressure Switch contacts and that signal should show 50 psi or better with the engine off. With the clutch engaged - 50 degrees or better at the Condensor - the signal should rise to 200 psi and engage the main fan. A manifold gage set is necessary to evaluate charge and any system problems. If you don't want to buy one (about $80 to $100) have a shop check it out.

 

This is correct and my mistake. Had some sparse info at work should have known better. Check it out at home with the books and information was obvious.

Would like to still hear the outcome from Al90Vette.