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Why is AC clutch cycling too often?

mikeceli on Thu June 28, 2012 5:54 PM User is offlineView users profile

Year: 1983
Make: Chrysler
Model: Cordoba
Engine Size: 318
Refrigerant Type: R143A
Ambient Temp: 70 F
Pressure Low: 15
Pressure High: 225
Country of Origin: United States

Hi Folks! My 1983 Chrysler Cordoba was "Professionally " converted to R134A, by the previous owner. At 70 F ambient, I get the following

When the readings reach Low side 15 PSI High 225 the compressor clutch cycles OFF

and stays OFF till the Low hits 40PSI and HIGH drops to 110 PSI, Cycles ON. AIR DISCHARGE 42 F during this operation.

Bypassing the LOW PSI Cutout switch. makes NO DIFFERENCE.

Buy passing the Clutch cycle switch (the switch w/ the capillary tube) causes the compressor to run constantly, LOW 10 PSI HIGH 200 PSI

with 35 F air coming out of the AC Duct.

I installed a new Clutch Cycling Switch, with new HEAT SINK GREASE, no change.

I KNOW I have a leaking AC hose.

Am I low on R134A? What say youse? Thanks!!

God Bless America!

mk378 on Thu June 28, 2012 6:50 PM User is offline

Your system seems to be operating properly. The switch prevents the evaporator from getting too cold. Air at about 40 F means the evaporator itself is near 32 F. Should it get below 32, the evaporator will ice up and the system can't work. You can't get 35 F air in normal climates without icing problems.

If the 42F air is not keeping the car cool enough, there could be a problem with the interior fan or ductwork restricting the airflow. Leaves and mouse nests are commonly found in the fan area, the debris will clog up the evaporator.

Edited: Fri June 29, 2012 at 7:16 AM by mk378

mikeceli on Fri June 29, 2012 3:56 AM User is offlineView users profile

No other car I can recall working on or owning, had the clutch cycle, that much. (Unless obviously low on charge).

Though I have limited AC service experience, I often get 35 F output temp, inside the car, with out freezing.

I am not yet, convinced, my Cordoba is performing normally. What about the LOW side PSI dropping to 15 PSI?

I am not trying to argue, I just don't understand and would like a little more "KOOL"!


God Bless America!

Edited: Fri June 29, 2012 at 11:56 AM by mikeceli

mikeceli on Fri July 06, 2012 2:28 AM User is offlineView users profile

God Bless America!

mikeceli on Fri July 06, 2012 2:29 AM User is offlineView users profile

Any other input? 107 hits and 1 comment.

God Bless America!

buickwagon on Fri July 06, 2012 3:43 AM User is offline

Originally posted by: mikeceli

I KNOW I have a leaking AC hose.

Am I low on R134A?

That kind of answers itself.

Recover the refrigerant, fix the leak, recharge with the correct amount and then see what happens.

"Correct amount" will probably be somewhere around 10% less R-134a than R-12 by weight, if no components were changed that would affect the volume of the system. Theoretically, the professional who did the conversion should have indicated the amount on a new under-hood sticker.

Also, R-134a has slightly different characteristics than R-12. If the original condenser was not changed out, the system may not be optimal. If the original mineral oil charge was not drained/flushed out, the system' interior volume is effectively reduced. The low pressure cut-out of 15 psi actually sounds a bit low, like someone was trying to compensate for poor efficiency. 23psi is a more common low pressure cut-out for R-134a. Perhaps this is a sign that the conversion process was nothing more than installing 134a style connectors?

I've saved hundreds on service by spending thousands on tools.

JJM on Sat July 07, 2012 4:48 PM User is offline

Charge is probably a little low, but it's kind of hard to check at 70F ambient.

You should also check the evaporator for airflow restriction, which can cause cycling due to lack of heat load on the system. After nearly 30 years, especially if this was a smoking vehicle, the evaporator probably has lots of gunk on it. A good bath certainly can't hurt, and air will probably be fresher.


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