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Compressor cycling at high ambient temps

redlightning93 on Sun May 10, 2009 10:17 PM User is offlineView users profile

Year: 2000
Make: Chevrolet
Model: Malibu
Engine Size: 3.1
Refrigerant Type: R-134
Ambient Temp: 88
Country of Origin: United States

For the last couple of years the Compressor will cycle for about the first thirty minutes of operation under higher ambient temps. Today I started the car, after sitting out in the sun for several hours, with ambient temp of 88* and under high blow operation the compressor would cycle on and off and would not bring the interior down to a comfortable level. This only happens under higher temps as later this afternoon, with ambient of app 80*, I started the car and the compressor held in fine dropping the interior temps rapidly as it should. Also, the recirculate mode will not hold for more than a minute or so returning itself to the normal mode. You can force it to stay in recirculate by manually holding the button down but as soon as you release the button it returns to normal.

Having bought this car new I know it is a virgin system and has never been serviced at all. I have not put gauges on it so I have no idea of pressures but intend to start checking it out soon. My first thought would be a HPCO switch but would appreciate any input as to where to start looking.

Edited: Sun May 10, 2009 at 10:20 PM by redlightning93

Matt L on Sun May 10, 2009 10:52 PM User is offline

Virgin system but with ten years of use, is not really virgin. It has likely lost enough refrigerant to cause trouble. Could be the LPCO switch.

Given that there is a (slight) possibility that you still have a full refrigerant charge, the airway could be a problem. Well, it probably is a problem anyway, which will show up as a very high head pressure once you get the system properly charged.

Chick on Sun May 10, 2009 10:59 PM User is offlineView users profile

Get the pressures and post the low and high side when it kicks out and when it kicks back in, no sense guessing.. hope this helps..

PS: Make sure the condenser fan is operating when the AC is on...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Edited: Sun May 10, 2009 at 11:00 PM by Chick

NickD on Mon May 11, 2009 11:03 AM User is offline

Pressures are worthless as air conditioning has the key word of AIR flow before taking proper pressure readings. On a ten year old vehicle common to find layers of debris on the face of the evaporator and a condenser loaded with bugs, also can find a pile of it between the radiator and condenser with even more bugs jammed in the radiator fins. Proper blower and radiator fan operation is a must.

Can't really call myself an AC mechanic as 90% of my time is spent cleaning, so more like an AC janitor, with proper air flow, then you can get accurate pressure readings, so the air flow part comes first. Removing the blower motor generally gives access to the evaporator and you figure the blower squirrel cage is more of a debris chopper than anything else, always find a mess in there plus a huge mess after you remove the fresh air intake grill.

With a ten year old R-134a system with the EPA jumping all over the techs, but not the OE's, some if not a lot of R-134a loss is common.

GM Tech on Mon May 11, 2009 4:38 PM User is offline

Well, since V-5s do not cycle by design, it has to be be high pressure cut-outs, so I would assume your cooling fan(s) are inop...I'd check them as well as the suggested pressures.

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

redlightning93 on Mon May 11, 2009 8:24 PM User is offlineView users profile

OK Guys, thanks for all the response and lots of good advise.

I now have pressure readings:

Ambient temp: 79*
Humidity 69% (Typical lower Alabama)
Low Side 28+
High Side 165+
Vent 42*
Static 90 (High and Low)

RPM's were app 1800 and fan was placed in front of Rad. Blower fan on high and doors open.

Both electric cooling fans are operating with A/C on.

Now, the compressor will cycle after about three minutes operating with these pressures, kick off and then stabilize to 90 lbs for a short while and then kick back in and will repeat this over and over. Once, the pressures got to 40 low and 310 high and just about the time I was ready to shut it down, the compressor shut off and after it stabilized the pressure went back to the 28/165.

Its hard to believe that air flow could be a problem as the condenser is relatively clean with just a few bugs. I can't say about the evaporator as I have not pulled the fan motor but seems to get plenty of air out the vents.

So, again I appreciate the help as I have been a lurker here for a while, just trying to learn as much as possible, but would really like to repair this system myself with your help.



Edited: Mon May 11, 2009 at 8:52 PM by redlightning93

bohica2xo on Mon May 11, 2009 9:45 PM User is offline

Since this is not a cycling system, you may need to connect a test lamp to the actual clutch circuit to see if it is staying energized during the cutout.

Obviously pulling the charge & weighing it would be a good reference, but with 40f vents on high blower with the door open I will say the charge is not too bad.

Alabama is bug country. Just because no big ones are smashed on the front of the condensor, you are not necessarily "clean". The little ones (gnats etc) get stuck deep in the fins, and can really cause a blockage. On a 9 year old car, it is time for a deep cleaning of the air path.

Use a strong surfactant like Simple Green or Zep Citrus, and spray it full strength deep into the fins on a cold condensor. Let it soak for a few minutes, then hose it out with a low pressure (garden) hose. You will be surprised at what comes out. It may take a couple of cycles to see clean rinse water. The surfactants dissolve bugs just fine. For really stubborn stuff you can use floor wax stripper, but this can be hard on paint so be careful if you do.

You may have to remove the grille to get a good shot at the condensor, but it is worth it. A droplight in the engine bay at night will let you look through the heat exchanger stack without tearing it down. Look straight through the condensor from the front of the car. If you see any spots that are blocked, there is probably some trash between the condensor & radiator.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

GM Tech on Mon May 11, 2009 10:18 PM User is offline

The key to this problem is whatever caused the 310 psi high side-- and why is it intermittent- could be some internal blckage as well- but that is pretty rare- once you get it to rythmatically cycle- put the garden hose to the condenser- see if pressure drop like a rock- and it quits cycling- that transducer should shut off compressor at about 427 psi, and on at about 300psi- so are your gauges accurate?

A "stall-saver routine will also shut off the compressor, when engine rpm drops to about 500 rpm..-- is engine rpm getting very low-- this could happen if the compressor is causing an excessive load, or another component, like a water pump, alternator etc-- the engine will sacrifice a/c compressor to avoid an engine stall-- so this is another way the non-cycling system will cycle- especially if high side never sees 400+ psi. You may want to unbelt, and spin individual components- even the compressor, again if high side is not seeing 400+......Just my thoughts..

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

redlightning93 on Mon May 11, 2009 10:49 PM User is offlineView users profile

"Since this is not a cycling system, you may need to connect a test lamp to the actual clutch circuit to see if it is staying energized during the cutout."

Good idea and after thinking this thru I am wondering if the air gap on the clutch could be the problem?

"Alabama is bug country. Just because no big ones are smashed on the front of the condensor, you are not necessarily "clean". The little ones (gnats etc) get stuck deep in the fins, and can really cause a blockage. On a 9 year old car, it is time for a deep cleaning of the air path."

You are right and I will be cleaning the condenser to optimize the air flow.

"The key to this problem is whatever caused the 310 psi high side-- and why is it intermittent- could be some internal blckage as well- but that is pretty rare- once you get it to rythmatically cycle- put the garden hose to the condenser- see if pressure drop like a rock- and it quits cycling- that transducer should shut off compressor at about 427 psi, and on at about 300psi- so are your gauges accurate?"

As far as can be determined the gauges are right GM Tech, but am I confused here that maybe I should be seeing presures of 300 to 427psi?

"A "stall-saver routine will also shut off the compressor, when engine rpm drops to about 500 rpm..-- is engine rpm getting very low-- "

No, engine never idles lower than about 700.

Edited: Mon May 11, 2009 at 10:52 PM by redlightning93

GM Tech on Mon May 11, 2009 11:10 PM User is offline

Malibus also have the irritating goofy a/c control head intermittent problem-- when system shuts off IS the green light on or off on the control head?

If t is off, and comes back on when a/c compressor comes back on, then therein lies your problem-- the fix is to clean the brushes contacts on the master on-off switch (which is the blower motor switch also) Take out the control head- remove the blower motor selector switch- then use a pencil head eraser and clean the brushes wiper area- it works every time- I have done about a dozen-- but most folks tell me the a/c light is off- don't say the a/c system is cycling- is also a problem on the sister vehicle, the Intrigue

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

redlightning93 on Mon May 11, 2009 11:34 PM User is offlineView users profile

Quote
Originally posted by: GM Tech
Malibus also have the irritating goofy a/c control head intermittent problem-- when system shuts off IS the green light on or off on the control head?



If t is off, and comes back on when a/c compressor comes back on, then therein lies your problem-- the fix is to clean the brushes contacts on the master on-off switch (which is the blower motor switch also) Take out the control head- remove the blower motor selector switch- then use a pencil head eraser and clean the brushes wiper area- it works every time- I have done about a dozen-- but most folks tell me the a/c light is off- don't say the a/c system is cycling- is also a problem on the sister vehicle, the Intrigue

Ahhhhh, this my friend sounds like my problem! Yes, the Green light goes off and on each time the compressor cycles. I will try this as soon as I can and let you know the results. Thanks!

GM Tech on Mon May 11, 2009 11:54 PM User is offline

Here is a link that may help you-- just search for malibu control head

malibu contol head - intermittent

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Edited: Mon May 11, 2009 at 11:59 PM by Automotive Air Conditioning Information Moderator

TRB on Tue May 12, 2009 12:00 AM User is offlineView users profile

I edited the extra https out of the link.

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

redlightning93 on Thu May 14, 2009 8:22 PM User is offlineView users profile

Quote
Originally posted by: GM Tech
Malibus also have the irritating goofy a/c control head intermittent problem-- when system shuts off IS the green light on or off on the control head?



If t is off, and comes back on when a/c compressor comes back on, then therein lies your problem-- the fix is to clean the brushes contacts on the master on-off switch (which is the blower motor switch also) Take out the control head- remove the blower motor selector switch- then use a pencil head eraser and clean the brushes wiper area- it works every time- I have done about a dozen-- but most folks tell me the a/c light is off- don't say the a/c system is cycling- is also a problem on the sister vehicle, the Intrigue

ITS FIXED!!!!

Thank you Mr. GM Tech! Also, thanks to all the others that posted very good information trying to help me repair my problem.

I can't believe I have lived with this problem for over 2 years and it was such a simple fix. The compressor stays on as it should now and it will stay on recirculate instead of defaulting back to normal after about a minute. This forum is such a help and I so appreciate the information from everybody.

Thanks again

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