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AC Compressor Cycles When Very Hot Outside


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Ron007
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Jun 24, 2012, 10:34 AM

Post #1 of 29 (2679 views)
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     AC Compressor Cycles When Very Hot Outside  

I have a 2009 Ford Focus SEL 2.0L 35K mi. I have had two dealers look at this and are stumped. Here's the low-down. When it is 90 outside or hotter and the car has been sitting in the sun, the air coming out of the vents is just cool. I noted the vent air was not continuous and you can feel the compressor engage and for five seconds, or so, and then release when on the freeway.

Dealer says they checked (was over 90 outside) the vents and the air was 45 degrees, pressure differentials and freon levels were in tolerance. No problem.

My big question is: shouldn't the compressor stay engaged until the evaporator freeze switch activates? Even when it is raining outside and the defog is on (compressor on) the compressor will not stay engaged and the defog operation is sporadic. I use the compressor to as a "jake brake" going down this long hill. (AC w/o recycle, full fan, not cold outside) The compressor will not stay engaged.

Please help! Dealers think customers are generally clueless (maybe they're right!) so I cannot get through to them. I've been following this issue for two years.

Thanks so much.


Tom Greenleaf
Ultimate Carjunky / Moderator


Jun 24, 2012, 10:48 AM

Post #2 of 29 (2674 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

That new and fairly low on miles this could be a high pressure cut out switch sensing over the limit, not in spec or heat just can't get enough air thru the condenser.

Get the best look you can at how clean it is from whatever - bugs, foliage garbage, plain dirt. Some can trap stuff in between condenser and radiator that you can't see easily. No harm in rinsing thru it with garden hose spray (do when cool) and see if junk comes out.

From there you may need and should get some pro A/C help. If fan(s) don't come on and stay on with high heat that's a problem of course,

T
_________________________________________
Long retired now


Hammer Time
Ultimate Carjunky / Moderator


Jun 24, 2012, 10:57 AM

Post #3 of 29 (2668 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

The bottom line here is that you have 45 degree air coming out of the vents. Assuming that was tested while on high blower, that pretty much put the issue to bed.




~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Veteran / Moderator


Jun 24, 2012, 11:44 AM

Post #4 of 29 (2635 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  


Quote
When it is 90 outside or hotter and the car has been sitting in the sun, the air coming out of the vents is just cool.


It takes a while for the AC system to transfer the heat from inside the cabin to the atmosphere. Your not going to get instant cold air if the vehicle has been sitting in the sun at that temperature.

Compressor is going to cycle depending on what the HVAC module is seeing as an evaporator discharge temperature and what the PCM is seeing from the TPS and ac pressure transducer. All these things would have to be monitored to see if the engagement and disengagement of the ac clutch is appropriate.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Sidom
Veteran / Moderator


Jun 24, 2012, 1:46 PM

Post #5 of 29 (2600 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

What you can do is get your own thermometer (a verified acurate one) put it the vents and check the temps. You can't go by "feel". Like the others mentioned an a/c system works by removing the heat from a cab (not putting in cold air), if its been sitting in the sun in 90+ degree heat it is going to take a while before the air "feels" cold.

One thing you can do to help would be to use a sun shade when the car is sitting. The next time its been sitting in the sun, put your hand over the dash board and feel the heat coming off it, this is basically a "heater" adding more heat into the cab that needs to be removed by the a/c system before the cab is going to feel "cold".

The hvac box where the evap is, is sealed so even though if feels hot in the cab when the temp reachs the cutoff in the box the compressor will cycle.






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(This post was edited by Sidom on Jun 24, 2012, 1:48 PM)


Tom Greenleaf
Ultimate Carjunky / Moderator


Jun 24, 2012, 2:00 PM

Post #6 of 29 (2593 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

Yes as Sidom said - an accurate reading of actual temp while driving around and sitting still.

Other from top/first post. Not the issue IMO but what is with "Jake Braking" via A/C? Engine would be at the same idle speed to cover that load so I can't see that as doing anything helpful?

T
_________________________________________
Long retired now


Ron007
User

Jun 24, 2012, 3:40 PM

Post #7 of 29 (2576 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

These are all excellent comments.

- The airflow through the condenser is clean.
- I had an 07 Focus and it worked great. You could chill your root beer at the vents (like normal good AC, these days) - this guy is different.
- I understand totally about BTU removal when the cabin is toasty. I have accounted for that.

Remember, this phenomenon is in conjunction with the compressor CYCLING. It will only engage for a short while during failure. When the air at the vents starts getting chilly, it will disengage. Air will then warm up at vents. Again, fan on max and air from outside. Compressor should stay engaged.

I agree, it seems to be either pressure switch (problem likely at higher RPMs like on frwy) or accumulator. I wish I could hook up an LED or lamp to show the tech that the compressor is, indeed, cycling. When it comes on in a Focus, you KNOW it!!

Thanks folks. Appreciate the brainstorming. I want to take to a real AC specialist, but I have an extended warranty through Ford. So....


(This post was edited by Ron007 on Jun 24, 2012, 3:43 PM)


Tom Greenleaf
Ultimate Carjunky / Moderator


Jun 24, 2012, 4:18 PM

Post #8 of 29 (2565 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

If you have an extended warranty to cover this than if you mess with it and they know it you are screwed IMO. It can cool so I don't think any of us think this is a refrigerant problem but rather as it seems that both higher speed and presumably higher extended RPMs are allowing this to cycle too much.

Either high or low on a CCOT system which it must be if you mentioned an accumulator could do this OR even an air dam under bumper if missing at speed might actually hurt airflow thru condenser, fan(s) or not creating pressure on engine side from air speed under the car. When tech(s) tested it, it wasn't in the conditions you seem to have the issue with.

If your warranty place doesn't have the equipment they should send it out or go for a run and witness this even with gauges attached, placed under and held by tape or wiper so they can see actual pressures when this happens driving the car. It's really theirs to figure out with warranty. If you can, take them for a ride or let them drive it and witness it if no other testing is helping them,

T
_________________________________________
Long retired now


Hammer Time
Ultimate Carjunky / Moderator


Jun 24, 2012, 4:30 PM

Post #9 of 29 (2557 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

This is an expansion valve system so it shouldn't be cycling. In order to diagnose it properly, it requires a set of professional gauges and a factory/professional scan tool. You have to compare actual pressures with reported pressures in the computer to analyze what is happening.




~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Ron007
User

Jun 24, 2012, 5:27 PM

Post #10 of 29 (2547 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

oh, trust me... I am NOT going to screw with the system. I know enough not to stick my hands under the hood these days, even though I've done all sorts of major repairs (engine change, transmission repair, etc.). The visual system (panels, cores, etc.) are all in exceptional condition. I am thinking it is an accumulator switch. I will try some 'in place' tests with revs up and someone actually looking at the compressor. Perhaps we'll be able to see if the problem is see-able. It just seems like the Ford dealer is stuck to primitive diag charts and quick checks instead of doing thorough work ($$). Feel like I'm over the proverbial barrel!

I seriously doubt they will hook up manifolds and drive the car monitoring the gear! I may pay my pro specialty AC dude for a consult - like we do with docs.


Hammer Time
Ultimate Carjunky / Moderator


Jun 24, 2012, 5:52 PM

Post #11 of 29 (2543 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  


Quote
I am thinking it is an accumulator switch


Not only does it not have an accumulator switch, it doesn't even have an accumulator. You just need to leave it alone.




~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Sidom
Veteran / Moderator


Jun 24, 2012, 7:07 PM

Post #12 of 29 (2532 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

I'm not around my data base to pull up the exact specs on this system but going off what you are saying we'll assume the charge is correct and this is an intermittent electrical problem (I would verify the charge 1st)
There is basically one of 2 things that could be happening either the PCM is ungrounding the relay due to bad input info it's gettting or the there is something failing in the clutch circuit.
If you have a good enough scanner, you can monitor the a/c relay pid and if the pcm is ungrounding the relay causing this problem, then you have to find out what input is causing the pcm to kill the a/c. If the problem is happening & the pcm is still grounding the relay, then something in the clutch circuit is failing. But at least that will help narrow the search, a clutch problem would be way easier to track down






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Ron007
User

Jun 24, 2012, 7:30 PM

Post #13 of 29 (2521 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

As reported earlier, the last visit to the Ford dudes, they said that the pressures are good, the differentials are good, the freon level is good (of course!). I asked about picking up computer data and he said (in so many words) there is no data. I am ready for a showdown at the not-OK Ford corral.

Good info on no accumulator. That totally hosed my guess. So the pressures are relayed to the PCM which controls the cycling. Now THAT makes a lot more sense as to why the problem exhibits regularly when the cabin has been super hot and the outside is hot - especially after sitting from some amount of hwy driving.

Good fdbk folks. I really appreciate your comments. Good brains out there!


Sidom
Veteran / Moderator


Jun 24, 2012, 7:47 PM

Post #14 of 29 (2517 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  


In Reply To
I asked about picking up computer data and he said (in so many words) there is no data.

That is an incorrect statement. They are using and IDS and you don't get any more infor than that....There must of been a misunderstanding..... If the problem is electrical, either the PCM is getting bad info & shutting down the system until it gets good infor or there is a problem in the clutch circuit, whether it's bad a coil shorting out, to wide of air gap, bad ground, bad relay, bad power source, something. I can't see the car but if it's cycling rapidly like you say it is and the refrigerant charges is good and vent temp is too high, then it's an electrical problem becausing even a mechanical problem could affect the pressures and send bad input data to the pcm.... I'm gonna have to pull this system up and take a look.....now I'm curious






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Ron007
User

Jun 24, 2012, 8:16 PM

Post #15 of 29 (2511 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

in my dialog with the service interface, I asked if the tech if the computer had data for reference. He said there were no codes issued so nothing could be observed. Clearly he was thinking of engine malfunction codes. I should have insisted on speaking with the AC specialist - unlikely they would ascend to that. So you are correct, again, the interface was clueless.

I still like your idea the more I think about it. PCM - hot in engine bay and in the cabin - problem. That really fits if the PCM does, in fact, control the pump clutch. I have to look at an AC chart for this application. And a flow-chart.


Hammer Time
Ultimate Carjunky / Moderator


Jun 24, 2012, 8:44 PM

Post #16 of 29 (2507 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

Of course the PCM controls the clutch but only after it is entirely satisfied with all the input data that it monitors to make it's decision so don't assume there is a problem with the PCM.




~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Ron007
User

Jun 24, 2012, 8:48 PM

Post #17 of 29 (2503 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

10-04. But - it seems like the highest probability at this point. I just wonder if the dealer is skilled enough to troubleshoot this level of problem without "easter-egging" solutions!


Hammer Time
Ultimate Carjunky / Moderator


Jun 24, 2012, 8:54 PM

Post #18 of 29 (2497 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

No, it would be the lowest probability.




~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Sidom
Veteran / Moderator


Jun 24, 2012, 9:18 PM

Post #19 of 29 (2491 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

Don't misunderstand what I am saying.....I'm not saying it's a bad pcm, just the pcm may not be grounding the relay.
The pcm decides if the driver gets a/c, not the driver. The driver pushed the a/c button, which is seen as an "a/c request" by the pcm.
Then the pcm looks at it's long list of chores (data) an if one is not done, the pcm won't ground the a/c relay and the driver gets no a/c.
The list is too long to list but does include an overheating engine or altenator that isn't charging so even a defect ECT sensor or bad battery can cause the a/c not to work....

OR.... a clutch problem, that is why I suggested looking at the a/c relay PID. If the relay is on and the problem is happening, then it's not PCM related.....

A dealer is just like any other shop with experienced techs & less experienced ones. The one leg up they have is their techs do have access to factory training, equipment & lastest TSBS.

I'm not sure if there is a miscommunication or what going on. One thing I will mention is how info is relayed to them. If it's in a question form then fine but if they are getting the drift you are "telling them how to do their job" then you may be getting blown off. There is a lot of misinformation out on the net and I've been on the other end. Someone with a diag problem that's been at who know's what forum and telling me to run this test & that test that has zero bearing on the problem I can see in front of me. I'm not gonna waste my time arguing with them.....I'll just shut the hood & let their "online expert" fix the problem...

The info we are offering here is too help you understand the problem a little better, but at the end of the day, they have the car in front of them so they are the experts.






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(This post was edited by Sidom on Jun 24, 2012, 9:20 PM)


Ron007
User

Jun 24, 2012, 9:51 PM

Post #20 of 29 (2484 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

I understand.

The discussion had two phases. The initial problem reporting (no I never tell the service contact what to change out!) was a careful description of the symptoms and when they occurred. The second discussion was based on his reply that all the measurements (pressures, etc.) were nominal. Customer problem. I simply asked, knowing that some problems have reporting capability, if there were any computer dumps possible to illuminate a malfunction. That's all. I am diplomatic, not a pain-in-the-___.

And I don't intend to use this fine exchange of information to go blast someone with MY take on what they're doing wrong.

I need to help flush out the problem and then intelligently show them how it can be created and what I was able to see when it was failing. Just dropping the car off and telling them to "fix it" for a problem that is high intermittent without doing my part somehow is not good. I appreciate you attitude adjustment safety. I have never put off any auto mechanic for any reason. We work as a team to handle issues. I must say, however, in that I have been lied to so many times, I like being armed with information to flush out being tech-fogged with BS - it has happened several times to me and many times to my daughters.

(you must get a lot of turkeys here!!)

peace.


(This post was edited by Ron007 on Jun 24, 2012, 10:06 PM)


Sidom
Veteran / Moderator


Jun 24, 2012, 11:30 PM

Post #21 of 29 (2466 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

Thats a good way of going about things....
One other thing I will mention and it's especially important on these werid intermittent problems but sometimes it's actually best to talk to the tech doing the work if possible...

That can actually be a problem sometimes where a customer gives some very good info on the problem and it doesn't make it from the service desk to the tech. He just gets a WO that says "a/c not cooling".

Customers can be the best source of info on problems like this. Most techs won't mind a customer decribing a problem, things that recently happened or recent work done or even going on a test drive. That can really help narrow the search.

Now once you start telling them what tests to run or systems to check..........welll..............hmmmm leave that up to you ;)






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Ron007
User

Jun 25, 2012, 12:24 AM

Post #22 of 29 (2456 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

I've decided to purchase time with a tech at an AC joint I respect. This guy knows his stuff. I feel more comfortable with him than the dealer. If he sees something, I may be able to pass that finding to the actual AC tech at the dealer.

You are dead on re simple descriptions. I did, however, tell the agent that he could call me anytime to discuss the issue personally. Nada.

Extremelhy frustrating situation, indeed. Wish there was just a fuse I could change!!


Tom Greenleaf
Ultimate Carjunky / Moderator


Jun 25, 2012, 6:57 AM

Post #23 of 29 (2438 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

Ron007 - Yes try to talk to techs as Sidom just mentioned. If you simply tell one with your own research or worse a service manager that will just relay it on the errors happen with things like this. Go in an insist of a service or repair and you probably will get just that whether the problem or not - careful there.

No harm meant but I didn't think this was a CCOT (clutch cycling orifice tube) set up and mentioning an accumulator would suggest that. No matter, just know as the guys have expounded on about how involved computer controls are.

Things A/C being watched not limited to but include shutting down compressor (could behave like cycling) if computer finds things out of perimeters like pressures, temps right at compressor, high pressure. More and more are coming out with two speed fans and fans that will wait for the high side pressure to get to a certain point and shut off if vehicle speed is enough and more. This both depends on the boss(computer) getting the right input AND sending the right command and that's where the right scanner comes in. That if the actual tech (personal but I have a problem with service managers just deciding/interpreting what should be done) has the symptoms of what happens and conditions if not just all the time with assorted repairs.

Communication is key to targeting a fix and how to approach it. Things that plain behave when observed are naturally going to be dismissed at "No" problems found. If that dealer doesn't have the tech(s) or equipment they should be set up with a regular shop or another dealers of same brand that does or at least do that where I am,

Tom
_________________________________________
Long retired now


(This post was edited by Tom Greenleaf on Jun 25, 2012, 6:59 AM)


Ron007
User

Jun 25, 2012, 10:10 PM

Post #24 of 29 (2397 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

Appreciate that, Tom. The huge question that I need to know before my next attempt at "the visit" is: under normal conditions and a working AC system, what keeps the clutch engaged? If I can set that mode up (like defrost or AC with full fan and outside air, etc.) I can observe the clutch to see under what temperature combos it will begin cycling. Then I can reliably duplicate this setup and show the AC dude.

--Ron


Hammer Time
Ultimate Carjunky / Moderator


Jun 25, 2012, 10:31 PM

Post #25 of 29 (2392 views)
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     Re: AC Compressor Cycles When Very Hot Outside [In reply to]  

You've been told multiple times that you can't diagnose this problem without a scan tool. You have to read the same data that the computer is seeing.




~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.





AC Compressor Cycles When Very Hot Outside


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