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2001 Mercury Sable - AC/Idle/Mileage problem

This is a discussion on 2001 Mercury Sable - AC/Idle/Mileage problem within the Automotive Support forums, part of the Tech Support Forum category. I had the AC compressor and receiver drier replaced on my 2001 Sable wagon due to a clutch that went


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Old 02-16-2008, 08:32 AM   #1
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I had the AC compressor and receiver drier replaced on my 2001
Sable wagon due to a clutch that went bad.

I noticed from the day we picked the car up that the idle kept surging at least 200 and sometimes 400 rpm. It does this every 7 seconds or so. It's enough to pull the car forward at a light if you don't have your foot firmly on the brakes. My highway miles dropped at least 3 MPG. When I take the climate control out of AUTO mode the problems including mileage issues stop.

The repair shop says this is normal. It's not. This car never did this before the repair. They tried an idle air control valve which I didn't think would work and it did not.

Is there some computer configuration that needs to be be reset or a bad/disconnected sensor involved? It's cycling the A/C on off very frequently. It also doesn't seem to do it when in Park.

These guys seem stumped - help.

Thanks.

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Old 02-16-2008, 03:53 PM   #2
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Good Morning staatsof, I am not familar with that vehicle or that system but can describe how the system probably operates.

I suggest the computer would be receiving a signal when the aircon clutch is operated, this would likely allow fast recognition for engine idle for power increase to compensate for the extra load.

It is common for vehicles with air conditioning to have modified computers or contain different modules to those without.

It is likely that another thermostat in the system is calling for more cooling which is not present or available.

So this may suggest the aircon system is not producing effective cooling operation as expected.

This may suggest the system charge is incorrect or the expansion valve is not functioning correctly as expected, the system would gave been de and re gassed during the clutch and drier replacement process.

I do feel this is a safety issue and should be addressed ASAP.

I would suggest contacting the vehicle manufacturer technical section and explaining the condition under a Safety Item heading and request information as to what may be the problem cause.

At a guess I suspect there is a problem in the aircon where demand is not happening but engine is being up scheduled.

That frequent cycling seems out of whack and also possibly suggests something in the cooling process is odd.

This is just a guess, but it is not uncommon for a bit of odd material to enter the system when driers are changed or the system is opened, and for something to migrate to the expansion valve which may explain what is happening.

For your information the expansion valve is the device that allows a constant spray of liquified gas into the cooling box, (expansion system) this is a pressure controlled variable orifice that maintains a constant pressure spraying effect of the gas as it de-liquifies, any restriction in that path will produce poor cooling effect and may produce odd effects.

Others will have different ideas.

Cheers, qldit.

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Old 02-17-2008, 03:40 AM   #3
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Thanks for the reply. Yes I know it's very difficult to diagnose these things
remotely. It's trhe middle of winter here now and even though one doesn't expect a heavy A/C load at this time it is none the less used to de-fog windows and this happens automatically with the Ford based system when in AUTO mode. I suspect it may accomplish this through periodic cycling the AC sdystem on/off. But every 7 seconds is absurd.

I can verify that the AC is accomplishing that function so it's functional.

This system uses an orifice tube and I had that plus the receiver-drier and compressor changed.

What I think I need here is someone very familiar with the Ford system.
I had thought about an over-charged situation but I cannot explain the very quick cycling symptom with that condition. It's like something is not registering that the AC has functioned and so it keeps on asking for it.

The idle regulation is also too severe. I don't remember the car surging at stop lights to the point that either the car moves or you feel it at the brake pedal.

This has been a bad service job and I get very angry when they tell me "oh that's normal".

Thanks again for your input, a number of good leads to follow.

Bob S.
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Old 02-17-2008, 04:10 AM   #4
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Good Evening staatsof, yes the AC is the best defogger.

Actually the system in normal is probably controlled by a thermostat in the airbox, and I suspect it is not operating cooling efficiently so is calling for more cycling.

The fan speed might alter the cycling rate if that were so.

It is likely a second thermostat is used in the auto mode.

It will be interesting to see how this progresses.

Do you mean to say that system uses an old capilliary tube type idea!

I thought that was obsolete.

Most systems I have worked on are all expansion valves and I have replaced a few because of restrictions or blockages.

Anyway see who else might shed some light on it.

I expect it would be R134.

Cheers, qldit.
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Old 02-17-2008, 07:56 AM   #5
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vacuum leak
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Old 02-17-2008, 08:33 AM   #6
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Good morning
This ford uses a clutch cycling fixed orfice tube (CCOT) AC system hence the ac clutch cycling on/off frequenty.With thouse parts replaced and your symptons I would suspect an overcharge of R134 or oil.The oil charge needs to be computed very carefully with multiple componant replacement.A vacuum leak could couse engine surge and miliage problems but would not be effected by ac operation.an overcharged system would cycle repeatedly with the hi pressure sensor repeatedly shutting down the system.This would also put more load on the engine and the ecm would respond with by richinng the fuel charge.Also check electric cooling fan operation.Pressure swithes signal ecm to turn fan on for air flow thru condenser esp at low road speeds.With ac gauges connected look for high pressure spikes.In cold weather high side gauge shouldn't read more than 175 psi low side in the 20-30psi range. The gauge readings sound like the key to your diag.
Good luck.
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Old 02-17-2008, 12:25 PM   #7
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Quote:
Originally Posted by cardoc View Post
Good morning
This ford uses a clutch cycling fixed orfice tube (CCOT) AC system hence the ac clutch cycling on/off frequenty.With thouse parts replaced and your symptons I would suspect an overcharge of R134 or oil.The oil charge needs to be computed very carefully with multiple componant replacement.A vacuum leak could couse engine surge and miliage problems but would not be effected by ac operation.an overcharged system would cycle repeatedly with the hi pressure sensor repeatedly shutting down the system.This would also put more load on the engine and the ecm would respond with by richinng the fuel charge.Also check electric cooling fan operation.Pressure swithes signal ecm to turn fan on for air flow thru condenser esp at low road speeds.With ac gauges connected look for high pressure spikes.In cold weather high side gauge shouldn't read more than 175 psi low side in the 20-30psi range. The gauge readings sound like the key to your diag.
Good luck.
These were the first questions I asked but I did not know about how the CCOT worked since most my other vehicles utilize expansion valves, I have a lot of older cars. These questions were dismissed without even checking. Another source of my anger.

But your diagnosis makes the most sense given all the symptoms. Now if I can only get the shop to reconize their potential errors.

Thank you very much for the input.
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Old 02-17-2008, 05:59 PM   #8
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Good Morning Gentlemen, interesting thread, I have just dismantled one of these CCOT valves to see what made it "tick" and it appears to be very similar to an expansion valve the way it operates.

Would there be any chance that a lesser capacity valve may have been fitted.

There appear to be quite a few different types.

I have never replaced one previously.

Certainly sounds as if the "experts" that did this work are not quite as expert as might be desired.

Thanks for the explanation statsof, I never stop learning all this stuff.

Cheers, qldit.
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Old 02-18-2008, 08:48 AM   #9
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Good day
On most newer fords the orfice tube is usually fixed in the liquid line and held in place by a couple of dimples.To replace it requires cutting out that section of line and installing a orfice tube repair kit sealed with compression fittings or replacing the whole line assembly.If the old compresser didn't put debris in the system it's not really necessary.Basically the modern CCOT system is cheaper to build but a pain to service.As always good luck.
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Old 03-14-2008, 10:09 AM   #10
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OK, so here's an update. The original service place just plain refused to go any farther on this issue. They attempted to be clever by sending several technicians out for test drives (without me along) and then they came back and proclaimed nothing is wrong. They would not even put a set of gauges on the car to measure the AC system because "it was done right the first time". No point in wasting anymore time with these assholes.

It did it AGAIN immediately as I left their lot. They have zero explanation for why my mileage dropped from 24+ highway to 18+.

So fast forward and as I was leaving for an appointment with Ford dealer for a documented and qualified second opinion the damn thing FIXED ITSELF!

I had gotten warmer out 40-50F instead of 25-40F so I decided to wait until it was cold again and see if it returned.

It did get cold again but the problem has not returned. The system functions correctly. The idle fluctuates only slightly and about every 7-10 seconds. Mileage is back @ 24.4 highway.

I should be happy right?

*** is going on here? Does anyone have a good knowledgable idea of what has happened?

Before I drop my claim with the credit card company I'd like to have an idea of what could have possibly happened.

I also want to return to the place that blew off a 7 year customer with their bad customer service and "splain" to them what they missed.

Bob.:4
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Old 03-14-2008, 02:53 PM   #11
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maybe you have a small leak in your system still and it has leaked enough now to get within the correct pressures.

good luck on this one i doubt your problems are over just yet.
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Old 03-14-2008, 05:06 PM   #12
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Hi Staatsof
Budfan8's theory could be very true.The system pressure may have lowered due to to a small leak in the system.Time will tell.See how it works in warmer weather.Also could be debris cleared orfice tube sreens or excess oil charge finally moved to accumlator.Acts as an oil storage devise to a point.If they used R-134 with dye added(very common)you search for leaks with a blacklight.If there is dye in system you can usually tell by opening low side service port(near accumultor)and see yellow dye trace on threaded fitting under plastic cap.
Good luck
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Old 03-14-2008, 05:43 PM   #13
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Good Morning staatsof, it certainly sounds odd.

The only explanation I can think of is that there was some foreign material in the system that was affecting the orifice.

That could possibly make the system substantially inefficient and cause longer running times which could have bearing on fuel consumption and in cab temps.

That foreign material may have been pushed through and that could explain why the thing has come good.

If that were the case that material would likely eventually end up in the drier and the problem not recur.

I can't think of any other possible explanation.

Others will have different ideas.

Cheers, qldit.
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Old 03-15-2008, 02:08 AM   #14
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Ok, about the leak idea. This happend as though someone turned off a switch. Instantly it stopped doing it, well with in a day it went from awful to no problem. It was after the weather warmed up and I performed another 175 mile mileage test run for evidence against the shop. After the trip I found my mileage was decent and the surging stopped. At the beggining of that 175 mile trip it was still surging.

It certainly sounds like something "cleared out".

They do show a new orifice tube on the invoice so if they actually put it in perhaps they also introduced junk. That or enough of the oil is no longer in a position to cause trouble.

Could excessive oil do that? Cause an initial problem then settle in the accumulator? Will it come back as an issue? I do have a 1 year warranty.
If they choose to honor it ...

Now one last point. Before the clutch went out on this compressor back last summer we did have some issues with the system freezing up (I assume) and it would stop working for a few minutes. Usually I turned it off for 5 minutes and it would come back. This was only on very hot days after long periods of use. I also had the engine coolant overheat on one of those days going up a long grade. Only time that happened. The coolant was less than 2 years old and I do flush the system regularly. Is it possible that this caused the overtemp of the radiator? BTW I told them all about this which is why I insisted on them changing the orifice tube and and the receiver/drier even though they didn't think I needed to. So they knew all about this. We even flushed the cooling system again on a BG flushing machine right after the car overheated.

BTW, recent mileage check yielded 24.4 mpg in full auto AC mode. Before it "fixed itself" it was 18-19. That's significant.

Thanks for all the input.
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Old 03-15-2008, 03:03 AM   #15
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Good Evening staatsof, that overheating instance is interesting, on one occasion with a vehicle, I discovered a switch on the bottom of the radiator that was in the AC clutch circuit and opened at some specific temperature obviously to reduce engine load and heat generation.

The chances are your vehicle may also have one of these switches, it may be worth checking the wiring manual and if it does, checking it is actually working. (if you wanted)

The other situation of icing is quite common in high humidity situations and the process of turning the system off for a period is the general fix as far as I know.

Usually having different fan, temp and airflow settings helps to avoid it. (Higher airflow)

I don't know any other method to avoid it but one of the other fellows may know.

Contaminating a system with foreign material is difficult to avoid in some cases where a lot of work is carried out, a piece of "O" ring material or "swarf" from a flare fitting can easily be inadvertantly introduced with difficult installation work.

It is often interesting to cut a drier open and actually inspect what has been collected in them after years of service.

Although oil would be expected to remain in the compressor, it does constantly migrate throughout the entire system, the drier helps reduce this tendency, but oil still circulates, probably more as a mist in the lower pressure areas. The amount of added oil is quite critical and needs to be absolutely moisture free. I would expect the servicing people would have been pretty careful with this.
I would doubt that excess oil could cause your symptom.

As a general rule of thumb it is not a good idea to open any system unnecessarily and really not do too much interfering kind of work on these systems that are giving good service.

Drier replacements are recommended periodically but I suggest if the thing works well leave this until it needs servicing, or a problem part replacement.

Others will have different ideas.

Cheers and let's hope that thing keeps operating properly. qldit.

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