I have a 1991 Toyota Pickup 4WD, 22RE. How do I know if my Air Conditioning Clutch is going out? what are the common signs & symptoms?

 

First rule of problem diagnosis -- Go from the symptoms to the cause, not the other way around. Or, as Sherlock Holmes would say, "It is always a capital mistake to theorize before you have the facts, Watson. It biases the judgment."

So, what are your symptoms? Why do you think the AC clutch is going out?

AC clutches usually fail catastrophically, by the coil burning out, so that the clutch doesn't operate at all. The coil will usually fail open (clutch won't engage) or shorted (blows the AC fuse and the whole AC system is dead. Replace the fuse and it immediately blows again.)

If you're simply getting intermittent operation and/or poor cooling, it's more likely something else. Start with making sure you have the right amount of refrigerant in the system.

 

Cool air comes out. The blower works good. I replaced my Blower Switch, Blower Relay, and Blower Resistor.

After it runs for around 20 to 30 min it clicks. Still blows cool air. I feel my engine rpms change when this happens. It clicks several times a minute, sometimes it makes a loud yaw thud sound. All these sounds are coming out of my Cooling Unit under my dash. Could it be the Expansion Valve in the Cooling Unit that is the problem? Or...???

 

As I mentioned in a response to your earlier post on this subject, cycling happens when the refrigerant pressure is either too low on the low side (not enough refrigerant, or getting too cold), or too high on the high side (too much refrigerant, danger of rupturing something.) The wrong amount of refrigerant can cause this, as well as a clogged expansion valve (low side pressure will be too low) or clogged condenser (high side pressure will be too high.)

If you haven't already, have a knowledgeable person put some gauges on the high and low pressure ports and run it until it starts cycling. The pressures on the gauges at that time should point to the area of the problem.

The various pressure switches are all combined into a single device which resides under the dash, so that is likely what you hear clicking. Unfortunately, since both the high and low pressure cutoff switches are combined into a single device, it's not possible to use a meter to tell whether the system is cycling due to low pressure or to high pressure. That's why you need to put some gauges on it.

I would guess your AC clutch is just fine.

 

My A/C was overpressured, plus my Blower Resistor was corroded. Discharged and recharged my A/C at the correct pressure and changed the stuff I mentioned earlier. Works great now!

Thank RJR for pointing me in the right direction!

 

[Ya gotta love a guy who quotes Sherlock Holmes on engine diagnostics ...]

 

Sherlock is my favorite literary character:-) There are a lot of similarities between solving an automotive mystery and a criminal one.

Glad you got the AC fixed, tsh2014. Thanks for the follow-up and letting us know.