Engine Testing A/c Compressor

[boostfrk]

My A/C system is currently dead on freon, so the next time I got it charged I was going to convert to R-134a. I've read Jrichker's thread and how-to on doing the conversion yourself but I'll probably end up taking it to a local shop since they have all the machines and equipment.

Obviously I want to make sure all the components are in good shape before I take it in. I don't want to have to pay for someone else to replace the compressor or dryer, etc. The compressor has never kicked on, and when I jumper the switch at the dryer it still doesn't kick on. Is this indicative of a bad compressor? Is there another way to check the compressor and see if the clutch engages?

When it comes time to get the system charged, is there a specific kit for replacing all of the o-rings? Any guides about where all of these o-rings are located?

I'm sure I'll have to also replace the dryer, but I'm hoping I don't have to replace the compressor as well.

 

[jrichker]

Check the wiring for the A/C WOT relay for heat damage , broken wires and relay failure. The A/C WOT relay is mounted on the passenger side wheelwell below the MAF. If you have a 92-93 Mustang, the fuel pump relay is mounted there as well. It can be very easy to confuse the two relays.

The wire colors on the diagram below may help.

Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pin out
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92 PowerWindowWiring.gif

93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif

 

[boostfrk]

Check the wiring for the A/C WOT relay for heat damage , broken wires and relay failure. The A/C WOT relay is mounted on the passenger side wheelwell below the MAF. If you have a 92-93 Mustang, the fuel pump relay is mounted there as well. It can be very easy to confuse the two relays.

The wiring looks OK going to the relay. No broken, frayed or apparent damage to the wires.

How can I check the relay for failure? If the relay is bad, would that cause the compressor to not kick on when I have the switch jumpered?

 

[jrichker]

Get out your test lamp or voltmeter and start checking voltages.

Turn the ignition switch to Run
Look for 12 volts on the red wire.
The green/purple wire should have 12 volts with the A/C on and fan on.
Jumper the Low pressure cutout switch and the green/purple wire and the pink/lt blue wire should have 12 volts .
With the A/C on and fan on & the Low pressure cutout switch jumpered you should have 12 volts on the black/yellow wire. No 12 volts on the black/yellow wire and the relay has probably failed.
If there is 12 volts on the black/yellow wire, then the clutch coil or clutch coil ground is bad.