Contour Enthusiasts Group Archives Forums General Troubleshooting A/C clutch not engaging

I recently discovered that my air conditioner wasn't coming on. After doing some checking, we've found the following:

-A/C clutch relay is not engaging by itself
-There is power at the relay socket
-A/C clutch engages when manually jumpered
-When A/C clutch is manually engaged by jumpering, the radiator cooling fans do not come on
-Relay coil is good
-Blower fan does come on

It looks like something is not telling the system to engage itself.

Also, we can't identify which fuse that controls the A/C (looking in owner's manual).

Any ideas on this?

There is an AC pressure switch in the line that tells the clutch to engage at a certain pressure. You need to be sure that you have no leaks...if the 134a is low the clutch will not engage. If your pressures are ok, then I suspect the pressure switch has failed.

For early production 99s, Fuse F37 in the CJB provides power to the compressor clutch via the A/C clutch relay. The same fuse also powers the heater blower motor, so if it works, the fuse is fine.

For late model 99s, F23 in the CJB provides power via the A/C WOT relay.

As mentioned, the refrigerant charge might be low, the low pressure cycling switch might be defective, the high pressure cutout switch might be defective, one of several relays might be defective, the PCM might be defective, or there might be a wiring fault.

Start with a pressure test of the refrigerant charge with a proper guage. The low pressure switch requires about 45 psi minimum behind it in order to "enable" the system.

Steve

Thanks for the replies guys. Actually right after I posted this question we went out and checked the pressure...there isn't ANY.

It looks like when about 6 months ago when I hit an empty oil case cardboard box in the road and didn't APPEAR to have done any damage that I actually did! That would also explain why I didn't notice it until now, since it just started getting warm out.

Now I just need to find out where the leak is...

Swap out the relay anyway because it will go bad soon. Most of them are junk! Bad contacts on relays will burn up more coils and motors than anything else.