New Problem: A/C full 45 PSI goes on then off

[SMD69]

OK here we go.

I got a new A/C Compressor, Clutch, Low Pressure Switch.

The system is R134A

I have a gauge on it and it reads 45psi.

The car is on & A/C is on full

Switch turns on the Compressor and the 45 psi drops below 25psi in a matter of 3 seconds and the compressor turns off.

3 seconds later the PSI is now back to 45 psi and the compressor turns on and its a cycle that went on for 30 min. of on then off over and over every 3 seconds or so.

 

[Rob94]

What do you mean you filled the system to the green marker?? The proper way to charge the refrigerant is with a set of gauges. You either do not have a proper refrigerant charge, or the cycling swithc is defective.

 

[SMD69]

My guage goes by colors.

GREEN-full
YELLOW-over filled
RED- U B FUKED

As for the Swith I replaced that this morning and Autozones policy is if you open the little plastic bag it comes in then NO returns.

 

[Rob94]

I have had numerous problems with Autozone's cycling switches. If you bypass the switch by jumping the connection and the clutch engages, you are either low on refrigerant or the switch is junk. I'd check the refrigerant level with a more precise gauge, one that reads in psi. If the pressures are correct, then that AZ switch is defective. Autozone will replace a defective part. You just can't return it for a refund.

 

[SMD69]

Ok I topped off the R134A and it read 35psi. No more R134A will go into it at that point.

I put the 2nd new gauge on it that I got today and now it reads 30 psi.

Cluctch still wont turn on unlesss I jumper it.

 

[Rob94]

Get a new switch.

 

[SMD69]

OK here we go.

I got a new A/C Compressor, Clutch, Low Pressure Switch.

The system is R134A

I have a gauge on it and it reads 45psi.

The car is on & A/C is on full

Switch turns on the Compressor and the 45 psi drops below 25psi in a matter of 3 seconds and the compressor turns off.

3 seconds later the PSI is now back to 45 psi and the compressor turns on and its a cycle that went on for 30 min. of on then off over and over every 3 seconds or so.

Please HELP !!!

 

[rangerj]

Did you vacuum the system BEFORE you added refrigerant? Usually the vacuum in the system will draw in enough refrigerant to activate the low pressure switch. If you did not vacuum the system you should be thankful the compressor will not activate.

Moisture in the air in the system will do the same thing that water in the crankcase will do to an engine. rangerj

 

[SHOoff.]

You probably need more refrigerant, IIRC it takes 2.5 lbs

 

[Bizzy]

SMD69,

Sometimes it's more helpful and easier to keep track of if you make one topic and add to it as you go along, updating the original title to reflect the updates. As I read through your posts I found it very hard to figure out whether you were having problems getting the system to come on, or if you had a pressure problem. Plus you might keep getting answers on how to fix a problem that's already fixed. I merged your two posts together, hopefully this will make it easier for us to help you.

 

[sdpatt]

It sounds like the cycling switch is doing its job correctly. Thirty-five pounds static pressure is very low at the current ambient temperatures. For R134a and an ambient temperature of 80-90F, there should be about 75-85 psig in the system. You need a real pressure gauge that displays the temperature versus pressure scale.

It also sounds like you are adding refrigerant with the engine off. To properly charge the system you must have the engine running with the A/C to max with the compressor running. With the compressor pumping, the low pressure side (suction side) fill valve is at a reduced pressure to help draw the refrigerant from the can. You might want an experienced hand on hand when attempting this again.

 

[redalfa164]

According to the Helms ac troubleshotting section there should be at least 50psi in order that pressure switch to allow the compressor clutch to kick on I readed you have 35psi which is way to low.

 

[SMD69]

OK here we go.

I got a new A/C Compressor, Clutch, Low Pressure Switch.

The system is R134A

I have a gauge on it and it reads 45psi.

The car is on & A/C is on full

Switch turns on the Compressor and the 45 psi drops below 25psi in a matter of 3 seconds and the compressor turns off.

3 seconds later the PSI is now back to 45 psi and the compressor turns on and its a cycle that went on for 30 min. of on then off over and over every 3 seconds or so.

 

[CheckerSHO]

45psi static(system off) pressure sounds really low, and the fact that its cycling fast also sounds like its low. That, or your orfice is restricted causing the low side to drop real low and the high side spike high. It would really help to know what the high side is doing while all of this is going on. sounds like the switches and associated controls are probably doing their job.

 

[sdpatt]

Please read carefully: Your refrigerant level is low.

Please add more R-134a (through the low pressure valve with the engnie running) until the static pressure on a cold system (after an overnight rest) matches the value for R-134a in the pressure-temperature table here.

 

[SMD69]

Ok Engine on

AC on full blast

put in more r134a until it said 70psi Which is in the red on the gauge (overfilled)

AC pulses on the off and when it goes off the low presure says 25psi then jumps back upto 45 psi and turns on and as quick it turns on it goes off agin saying 25psi

I turn off ac and the pressure reads 70psi on the low side

I jumper the switch and turn it back on. And it wont take anymore R134A.

There is a metal hose coming out of the firewall under the evaporator and it is covered with white frost and runs to the passangerside of the ca and down.

The high side pipe 2" below the pressure valve is hot to the touch.

I am really lost here.

I took it to a shop and they wanted $149 to diagnose it. (no way)

 

[sdpatt]

Did you click on that link to the pressure/temperature table? A 70 psig static pressure in the morning with the engine off and cold would be an appropriate charge if the ambient air temperature was about 69F. I'll bet you checked the static pressure with the engine compartment hot. The static pressure with the engnie compartment hot would be more in the 100+ psig range. You should check it cold and you still need to add more R-134a.

And your gauge is very misleading. You are not overpressuring your system.

 

[SMD69]

I checked it an hour ago cold. I didnt use the car today.

It's 62 degrees out.

With the car off it reads 70psi

Car on 70psi

AC on 45psi turns on then drops to 25psi and off for 3 sec till it says 45 psi and then goes back and fourth

 

[projectSHO89]

Sounds like a restricted orifice or evaporator or there is moisture in the system.

You did vacuum the system, didn't you?

You really need a set of manifold guages so you can see what the high side is doing. Without that number, it's just guessing.

Steve