A/C Compressor cluch in and out every 4 seconds

[SDQFORD]

Please let me know if the A/C compressor have a problem is in and out every 4 seconds, any ideas about what the problem is? is maybe low gas in lines...help me please...thanks

 

[Four0Sport]

my 91 did that b4 i sold it.. so i just unplugged the wire hook up, the clutch and/or compressor could be low on oil, which runs with the freon in the line, or the clutch itself could be failing

 

[Skibug]

Check the pressure of the lines on the low side. The compressor will kick off when it senses a low pressure and then once pressure is bled off the high side it will kick back on. May be low on freon.

 

[Interstate]

When the compressorturns on and off like that, it means there isn't any freon in the system, which means you've probably got aleak somewhere. Did you let you X sit for a long time or not run the A/C for a long time?

 

[Jason94sport]

Yes what he said

 

[Jeeps&Fords]

It is perfectly OK for a 134 based system to cycle. In fact, most 134 systems will cycle on and off. If you have no freon, the compressor will not cycle at all. The best thing to do is to check the pressures.

 

[Glacier991]

a cycling condition does not mean you have no refrigerant. The clutch will not turn on without pressure in the system. This is to proetct against a run dry, because the refrigerant carries the lubrication. No pressure = No refrigerant= No Oil = ZAP.

The typical cycling issues is that the charge is low. Now for an odd reason I will not go into here... until a system becomes seriously low, the static - that is non-running -pressure will be the same on a fully charged system versus a partially charged system. (Ex. a half full can of rerigerant will have the same pressure of a full one).

That pressure will approximate ambient temperature in degrees F. So checking system pressure with the A/C off will tell you nothing in most cases, unless it is SERIOUSLY low. So rule 1 - you need to check the low side with the system running.

There is a protection switch will cuts out when the low side pressure gets down around 30 psi. In a fully charged system this protects the evaporator from freezing. (remember that temp = pressure thing?). On a hot day the compressor may run full time.... on a cooler day it may cycle frequently as the refrigerant is pumped OUT of the low side and into the high side, lowering the low side pressure eventually to the cutout perssure. Depending on how frequently it does this can be a clue to the system's charge, and you likely need to bring the low side pressures up by adding refrigerant.

Now back to that temperature thing... running the AC when the outside temps are near freezing means the system pressure is practically AT the cutout pressure before you even start... that can result in rapid cycling - obviously. The AC will run when the Defrost is on... (to dry out the air). The constant cycling in wintertime drives me nuts and I unplug it for portions of the winter. I don't do it ALL winter, it should be run frequently to keep the seals intact and lubricated.

There is a lengthy thread on AC in the Useful Threads forum... although it started out explaining a conversion to 134 refrigerant, by the end it was a thread ALL ABOUT AUTO AC. You might enjoy it. Lots of fun info.

 

[Jefe]

I have also seen the compressor cyle constantly where a system had been over-charged. (goes over pressure on the high side?) I'll assume this isn't your problem unless you've recently had it recharged.

 

[Glacier991]

Same can be true of a clogged system. (rare)

 

[Interstate]

The "BLACK DEATH" could cause that too couldn't it.

 

[Glacier991]

mmmm well I cannot say categorically no, but I'd doubt it is a Black Death case.

 

[mctoy]

For what it's worth,...Im an HVAC contractor in 5 states and as usual Glacier991's explaination of temp/pressure relationship and probable diagnosis (Low charge=leak) is darn near textbook! Get a can of interdynamics lube/charge (The small one, around $8 at Walmart) and put it in. Or, if you want you can pull the leads off the low pressure switch and jump them together and see if it runs longer. Note that if it is low (Probably) you dont want to do this for very long! (Just long enough to see if it will stay running) As Glacier said, the refrigerant flowing thru the Comp. contains the oil!
Good luck!