HOW TO FIND OUT IF A/C PRESSURE SWITCH IS BAD

You say you believe the relay is good. Just a thought, I have had a couple cars where the same relay was used for several things. If you have the same relay for something else maybe you can swap them to see if it works. I did this by putting the A/C relay in place of the fuel pump relay and found the fuel pump relay was bad. If you do this and the car will not run long you know the relay is bad.

if you have battery power on the large terminal at the starter and the same on the smaller wire when someone Is turning the key to start and the starter has a good ground then the starter is bad drawing too much amperage causing the clicking sound.

Yes they make a kit to bypass the system, check with your dealer, they can bypass it. If you want to make sure thats your problem, then you can go through this procedure:

The most common cause of a non-starting car is the battery. It is either weak, (low voltage) dead, (zero voltage) or has bad connections. (corroded or loose) I will assume you have a fully charged battery with good connections. (both to battery and starter relay)
If you remove the starter switch lead (small wire) from the starter relay and apply +12v from the battery to its respective prong or lead on the relay, and your starter cranks, your starter switch is faulty. (not to be confused with your key switch). If you jump the two large wires together on the relay and it cranks, then the relay is faulty. If you jump the two large wires together and nothing happens, then starter is faulty, or wires to starter are loose or broken. Picture of starter switch prong on the relay is pictured. NOTE: sparks are to be expected, so don't be too scared. Pictured is starter relay that is mounted seperate of starter, on models with starter/relay mounted together, its similar.

under the hood in the black main relay and fuse box.look for fuel pump relay.the relays most likely bad. or a loose wire to the fuel pump.has it been wrecked? have to ask yourself alot of questions when you bypass the pump straight to battery and it works. start with simplelest 1st. check main fuse relay and fuse panel 1st.then go to wiring harness that goes to the pump. thank you for choosing fixya.com.

If it has the auto air functions.On the passenger side under glovebox remove the black cover under the dash and there is a hidden fuse block with a ac fuse. Check for this a very common issue. Also if the ac is fully charged you can unplug the low pressure switch located on the accumulator( silver canister located by the relays towards the firewall) and take a wire and place between the two terminals just make sure the compressor will does come on.If the ac is turned on and you jump that switch and the compressor does turn and ac starts working then a good possibilty that the low pressure may be bad. Would check the fuse first.

First thing is to look at the a/c fuse and relay under the hood in the power panel. Possible blown fuse or a bad relay. If no blown fuse or bad relay found then go to passanger side of truck and you will see a black canaster with a low pressure switch on it. Remove plug to switch and using a jumper wire jump out the plug to see if the compressor clutch comes in. (have the truck running with the a/c selector switch on ). If the clutch comes on then it's either you have very little freon gas in system or the low pressure switch is bad and will need to replace it. Use small pliers to remove switch and replace it with a new switch, make sure it has a new o-ring inside switch before installing it. Hope this will help you.

When this happens, my first suspicion is that the system needs charging. If you don't have a gage to check the low side pressure, you can bypass the low pressure switch by removing the connector and placing a paper clip across the terminals in the connector. If this allows the clutch to engage, charge the system. If not, then read the diagram at the link to see other possible causes, such as the fuse, the relay, or the control panel.
http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=136025

If you look on the low pressure side of the AC system you will see a plug that is incorporated in to the line. It will have two wires leading to it. Remove the plastic clip that attaches the two wires to the sensor and use a short piece of wire to connect the two terminals in side the plug by putting the ends into the cap. This will bypass the low pressure sensor and allow the AC clutch to engage and begin to cycle again. Remember this low pressure switch is there for a reason. If you don't add more r-134 to the system and allow the AC compressor to cycle you will destroy the compressor. You need to charge the system when you bypass the low pressure switch and get the system up to full charge status and reconnect the switch.

The A/C pressue switch may be bad as well. Also the mode switch on the control head inside the vehicle. There are many other exsisting problems pertaining to a/c. I suggest a manual from Auto Zone for many faults can be noted especially wiring can be at fault

take it to the deeler