A/C Problem

[zx6-guy29]

OK, here goes. A/C is charged but clutch will not engage. I am thinking possibly a relay or pressure sensor. Any ideas?

 

[BrooklynBay]

Did you check the fuses?

 

[budwich]

As indicated check the fuses. After that, if you want to see if your compressor is functional, short the pressure switch which should cause your compressor to run. If it does and you get cooled air then perhaps the switch is faulty. If it runs and you don't get cool air then something else is wrong and don't let the compressor run in this mode without further checks probably at a service center.

 

[ExplorerDMB]

check your a/c clutch relay

-Drew

 

[BrooklynBay]

There is a diode that is connected to the clutch's coil that could have blown out. This is used to suppress the sharp voltage spikes with is also referred to as back electromotive force (EMF). If it is in series with the coil, then it could be open. If it is parallel, then it wouldn't be your problem unless it were shorted. That would cause the fuse to keep blowing out.

 

[zx6-guy29]

fuse is good, already checked that. As for the relay, once I pull it, how do I tell if it is bad? Dumb question maybe, but I have never had to mess with them before. Also, the pressure switch that I should short to test the compressor, is that the one connected to the compressor itself or is it somewhere else?

 

[budwich]

there is a "wide open throttle relay - WOT" but I wouldn't worry about that. The pressure switch is on the line near your fire wall by your accumulator / heater / fan. Unplug and there is two wires which you short together with the engine running and AC on. If the compressor kicks-in, then perhaps the switch is faulty.... HOWEVER, it could also mean other things. How do you know you have a "good freon load"?????

 

[zx6-guy29]

had my mech check it, he said there is pressure in the system.

 

[zx6-guy29]

ok there is more. I jumped the sensor, and the compressor kicked in, but the lines never got cold. There is definitely pressure in the system. What next?

 

[budwich]

Probably at my limits of knowledge on AC but I would suspect a plugged orfice tube which is causing not enough refrigerant to pass into the evaporator and therefore you get not cooling and low pressure causing the switch to be activated (ie. open). You have to probably take it to a service center where they have to remove the refrigerant, pull/replace the orfice tube and then refill the system assuming the the plug (if it was the case) wasn't a result of "bad things" like metal / rust "stuff" floating around inside the system. Maybe someone else will chime in with thoughts.

 

[BrooklynBay]

I was also going to mention the orifice/expansion valve, which is basically an inline filter. This balances the line pressure from the high pressure side to the low pressure side. What were the reading of both sides?

 

[Brock94]

had my mech check it, he said there is pressure in the system.

This doesn't mean there's enough refrigerant in the system-- the static (non-operating) pressure of the system will be the same whether there are 5 oz or 16oz of refrigerant in the system.

The best way to check how much is in the system is to recover it and wiegh it (I know that's probably not an option for you.) The only other way that you can correctly charge the system is to use a manifold gauge set (with both high and low pressures) and charge based on the pressure readings, ambient temperature and vent temperature. At a minimum, you should get a manifold gauge set if you are going to do DIY work on your A/C. Check out some of Glacier's posts on the subject-- he has a great post on r-12 to r-134a conversion that addresses a lot of these issues. (Probably in the useful threads forum).

Once you know there's really an adequate charge and you're still not cooling, then you can move on to other possible issues.

 

[Papa]

Brock94 is correct about 5 OZ of refrigerant giving you the same static pressure you would get if you had a fAull charge which I think is three cans. A set of gages can be had at Discount Auto for about $25.00 a whole manifold set is nice but you can get by with less.