The salesman’s explanation is totally correct as far as it goes. Chances are the “blend” door is not moving and the air is going in the default mode, which is generally to defrost the windows in bad weather for safety. When the door blocks off the heat, the AC can come through. The cause of the door not operating can be cheap or more expensive, but if they fix it, everything should work. It’s not enforceable unless the promise is in writing. Are you feeling lucky?
Took the car to a mechanic (an awesome guy, but that’s another thread). Because the dealer had just filled the freon, he said he couldn’t really test the system for leaks, but I could bring it back to him tomorrow.
Back to the dealer where I negotiated a one month warranty on the AC, everything covered.
The air blows fast and cold now; hope I won’t need the warranty.
Thanks to all, lots of good info provided here (as always).
mmm
Tell him time is money and you’re going to the lot down the block (so to speak.)
Ooops I see I’m too late.
Dealer added freon??? Red flag.
There were some GM cars from the 70s through the 90s that used a centrifugal compressor that routinely leaked a small amount of freon and oil out of the front seal when it became slightly worn. You’d have to add freon to these cars at intervals. In fact, the owners manuals on these cars would tell you to run the AC at least weekly for 5 minutes or so year 'round in order to keep the lubrication on that seal from drying out and leading to wear and a leak.
I am, however, unaware of any later vehicle or vehicle of a different brand that routinely leaks freon, and I’ve never seen a Ford that needed that kind of service.
If freon had to be added, the system is leaking. If the system is not leaking, then it doesn’t need freon.
Finally a good answer.
Two things to check
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A/C clutch operation
a. with the A/C off, open the hood and see how the A/C compressor is operation.
b. with the A/C switch ON, the clutch on the A/C compressor should have engaged -
As AlBundy says, check the blend door operation
the air is routed into the HVAC system through the A/C heat exchanger and the heater core. The percentage of air through each path is controlled by the temperature control switch in the cabin. If the path through the A/C heat exchanger is blocked, then only hot air will be driven through the vents even if the A/C compressor is working and there is enough refrigerant in the A/C system–no air flows over the cooled coils and into the vents and therefore not cold air.
Usually this is caused by a disconnected/damaged vacuum hose because the default [failsafe] position of the blend doors is to route air 100% through the heater core path.
phxjcc - could you please clarify 1a? I assume the engine is running and the AC is off - not sure what I am looking for at this point.
And while we’re here…
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The mechanic (not connected to the dealer I went to) told me the system is low on refrigerant. He pointed to the compressor cycling on and off with the car running and AC on as evidence of this. Does this sound correct? (he had no reason to lie to me, he spent a half hour looking over and driving the car and charged me nothing).
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The clutch on the compressor does engage, as described above. Does this mean the compressor itself is OK, or not necessarily?
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The dealer/salesman showed me the part they replaced. It is a cable about a foot long with two wires at one end and a plastic component on the other end about the size of a strawberry. He said they commonly fail in Ford Focuses (Foci?). Anyone familiar with this part?
ETA: Perhaps this cable part controls the “blend door”?
mmm
Can’t say I see the point to that either. Sorry to be critical, but I don’t see any value to you from that post.
A typical symptom of a system low on refrigerant is rapid cycling of the compressor clutch, as in every few seconds. Along with that there is generally insufficient cooling. The bottom line question is, does the system cool properly? It is normal for the clutch to cycle on and off – that’s how it regulates the temperature – somewhere around every 30 seconds to every two minutes, depending on factors like ambient temperature and humidity. I wonder about this mechanic’s competence because of his contention that it couldn’t be leak-tested shortly after the freon was topped up. That is simply not true. I’m suspecting this guy has that dangerous thing, a little knowledge.
What it specifically means is that the system controls are turning on the compressor. If the system cools, its operating pressures are within specs, and there’s no untoward compressor noise, then that tells us the compressor is working okay.
Pretty good bet it’s the mode cable assembly, which controls which ducts the air comes out of. According to my repair info, there is a separate cable assembly for the temperature control which controls the blend door (blends hot and cold air as needed to get the desired air temp out the ducts). This is contradictory to the dealer’s earlier contention that one part would affect both the stuck-on-defrost problem and the not-cooling problem. It sounds like the not-cooling problem was due to low freon.
Here’s the thing: with the system cooling properly now, it is fixed. However, the fix may not be permanent, in that it appears the not-cooling was due to low freon, and that means there’s a leak. What really matters is how big the leak is. If it’s pretty big, it will lose cooling during your one-month warranty period. If it’s pretty small, it could be too small to detect, and the system may need topping up every year or two – not uncommon, and in my opinion acceptable (what can anyone do if the leak is too small to find?). The worry would be if it’s a medium-sized leak that will require topping up in, say, two months. My thought is the system should be leak-tested now, and if a leak can be found it should be fixed.
You didm’t specify what kind’of vehicle it is, but I can give you some information based on personal experience. Oddly enough, both Chrysler products.
The first is our 2004 Jeep Grand Cherokee. The air stopped’respondimg to the controls and would only blow out of the defrost vents. This was an incredibly easy fix. The vacum line had worked it’s way loose fron the engine block. A quick look at the hose connections on the drivers side of the engine and I could visually see which. line had come lose. I was able to push the line back on the “tit” and problem solved.
The second was in our 2010 Dodge Ram that just went out of warranty. It started doing the same thing, a quick search on the internet and I discovered that the air direction is not controlled by vaccum, but rather it is done electronically. Notice how I’said’out’od warranty? Dodge is quoting $600 for the repair, so I guess we will live with it for now. Though oddly at times it will work and blow air from the correctly selected vents.
In short, it could be a very simple fix or a very expensive. I think that most vent designs are controlled by vaccum, so if yours is, it very well may be a simple fix.
The dealer just filled the freon and now your mechanic says it’s low? That can’t be good.
Conceivable the dealer didn’t get it full, conceivable it’s got a big leak, but seeing as it’s cooling and said mechanic thinks (wrongly) that you can’t leak-test when it’s just been filled, most likely mechanic doesn’t know what’s he talking about.
what the independent mechanic may have intended to mean was “that unless the leak was really big then you won’t see any leakage in a test now, wait and test in a day or two and see if it shows that it is low”.
No, if there’s a detectable leak (which doesn’t have to be big, just can’t be really small) it will show up. Refrigerant leak detectors claim sensitivity to leaks as small as one ounce per year; most systems contain 20-30 ounces.
The OP wrote “Because the dealer had just filled the freon, he said he couldn’t really test the system for leaks, but I could bring it back to him tomorrow.” This is nonsensical, there’s no way that just having it filled proscribes doing a leak test, and there’s no reason to wait a day.
Very very difficult to use an electronic leak detector on a car. The car’s fan and other moving parts stir the air quite a bit, and disperse the freon away from the leak. You’ll only find a gross leak with an electronic leak detector, and then only sometimes.
If you really want to search for a small leak, the best way is to use a dye pack. Inject it into the system (it’s compatible, if you purchase the right dye) then use a fluorescent light to hunt for signs of it on the outside.
Easiest way, as I stated previously, is just to do a careful visual inspection. There will be oil around the leak, and since that oil will capture dirt, there will be an oily, dirty spot around the leak. 99% of the leaks will occur in a joint or a rubber hose or the front bearing of the compressor. Those are the places where you look. Of course, it COULD be inside the dash. Isn’t usually, but could be. In this case, it is really painful to diagnose.
When you find a suspect spot, clean it up thoroughly, turn on the AC, then just use the old soapy water trick. If there is even a tiny leak, it will blow a bubble. Works well.
I don’t know where you got that idea, but it’s rubbish. There are electronic detectors designed for automotive use, and using them is standard procedure in the industry.
That would be a problem if one were ignorant enough to try to leak test with the engine running, but that’s not how it’s done.
That can work well for visible parts of the system, especially on the high pressure side. It’s often not quick, though – it can take days, sometimes weeks, for enough oil w/dye to leak out to where it can be seen. And it’s rather useless for leaks in the evaporator, which is out of sight enclosed in its case. (The dye flouresces in ultraviolet light, not flourescent light.)
There will sometimes be oil around the leak, but certainly not always.
This is simply wrong. Evaporator leaks (inside the dash) are not that rare, and on some models are fairly common. They are typically easy to find with an electronic detector if it’s used properly.
Again, no need to run the system. This method can work, but it can be messy and difficult to apply to less accessible parts of the system. Using an electronic detector is quicker, easier, and cleaner.
Re you Q? on 1a.
there is a relay involved in engaging the A/C compressor clutch. If this relay is shot the A/C compressor clutch will not engage. All I am saying is start as far upstream of the problem as possible and then progressively trace the problem downstream.
Well, I got that idea because I own one and have used others. Hard to use 'em in any but the most perfect conditions. Using one under the dash would work well enough; it is still under there.
That’s how it’s done if you want to find a leak that is more than a static leak, or a leak on the high side, which might not leak unless pressurized.
My bad. I wrote fluorescent when I meant UV. And, yes. It can take a long time for the dye to appear, but that means the leak is very small.
Oil is carried in the freon. If freon leaks, oil leaks. If oil doesn’t leak the system is critically short on oil. That’ll burn up the compressor in short order.
Well, all right. I only work on vehicles when I have to because they are such a PITA under the dash. So I can’t claim extensive experience with lots of different types of cars. I’ve only found a leak in the dash once, but perhaps I’ve been lucky.
Wouldn’t want to do it inside the dash, for sure. Works fine under the hood.
Don’t quite know how to tell you this, but the system is always pressurized. If it isn’t pressurized, either you are outside in the dead of winter, or the system is empty. Run the engine and heater until everything is nice and warm and you will have probably about 200PSI in all parts of the system with the engine off.
If the leak is small, then you want to use the electronic sniffer, waiting for enough refrigerant to leak to leave a dye trace, or a dirty oily spot can take way too long.
OH BTW soapy water is NOT an approved leak detection method for finding AC leaks in automotive AC systems.
To continue discussion with Bemused:
I gather that you’re knowledgeable about A/C systems, but I would guess that your experience is more in the home and industrial realm. I’ve been in professional auto repair for nearly 40 years. I’ve worked at a variety of shops, including several independents, a few dealerships, and a shop that specialized in air conditioning, and now have my own shop. I’ve installed A/C in cars (that goes back a few years :)). I’m ASE certified in air conditioning (and other areas - Master certification), I’ve been trained by one of the best there was, and have had ongoing training. When we’re talking about automotive A/C, this is my bailiwick.
To elaborate on some points:
Well, I got that idea because I own one and have used others. Hard to use 'em in any but the most perfect conditions. Using one under the dash would work well enough; it is still under there.
I, and my colleagues, find electronic detectors easy to use. Standard procedure is to do leak testing with the engine off. In my entire career, there have been maybe three times I’ve felt a need to leak test with the system running, when there was a suspicion of a leak that only occurred at very high pressure – it comes up only a fraction of 1% of the time. Actually going under the dash only applies to some older systems with exposed parts under there. Evaporator leak testing is done by turning the blower on and testing at the outlet ducts and/or the drain tube.
That’s how it’s done if you want to find a leak that is more than a static leak, or a leak on the high side, which might not leak unless pressurized.
As I mentioned, that is a very rare situation. Rest pressure is typically 80+ psi, which is more than sufficient to find virtually all leaks. High side operating pressure is in the 150-300 psi range, which only makes a difference in the most unusual circumstances. Low side operating pressure is 20-30 psi, obviously rest pressure is better for leak testing there.
Oil is carried in the freon. If freon leaks, oil leaks. If oil doesn’t leak the system is critically short on oil.
It’s just not always true that oil will leak out with the freon. Those oil molecules are bigger than the freon ones, and don’t always seep out through a hose when the freon does. Especially on the low side, it’s not uncommon to find a refrigerant leak with no detectable trace of oil.
[Re: soapy water testing.] Wouldn’t want to do it inside the dash, for sure. Works fine under the hood.
In my entire career, I’ve never seen it done or even mentioned in an auto repair shop. Without an electronic detector (or an old propane halide detector) it might be better than nothing, but a good detector will do the job better and easier, and using them is the norm.
This. To put it in even simpler terms: air temp and air direction are absolutely NOT controlled by the same parts. He’s a liar.
I had an idiot salesman try to tell me once when the ‘check oil’ light came on that it was my signal that the oil needed to be changed. Uh no… it means it’s low on oil, dipshit.
God I HATE most car salesmen… especially used ones. I even worked as a mechanic a some time ago; and I still find it so much less stressful to buy from CarMax. I respect their right to make a bit more of a profit; but in return they have NEVER given me a problem on fixing anything that came up during the 30 day post sale window.
Must resist the urge.
Must resist the urge.
Want to avoid the ban hammer must resist the urge.
Ah no the check engine light doesn’t mean you are low on oil. Where did you get THAT idea?
::: sigh::: it really is taking longer than we thought.
A check engine light means the ECM has detected something that will cause an increase in emissions.
The ECM don’t know oil level.