Car AC question?

[sublauxation]

I'm hoping somebody can help me with this one. Last night while driving my wife's Explorer the AC stopped blowing cold air abruptly. There was no sound, no squealing or scraping or anything. About 20 seconds later, with the AC still on, I smelled some burning rubber/electrical smell. I turned off the AC and the smell stopped. The serpentine belt is just fine and doesn't make any sounds at all.

The radiator fan and AC Condenser fan are both electric and mounted side by side. If I spin the radiator cooling fan it will do a full turn pretty easily but the AC Condenser fan wont do 1/4 turn with the same pressure. Both make some noise but the AC Condenser fan squeals pretty loudly.

Am I right that with an electric cooling fan there should be some resistance from the brushes but it should still spin relatively easily?

Then it would be likely that the squealing sound is bad bearings in the AC Condenser fan and that would likely be the burning smell?

If the Condenser fan stops working the system overheats and stops cooling?

And assuming this is all true could a minute at most of driving do anything bad to the compressor?

Hoping I'm right as the dual fan assembly is about $150 vs $1500 or more if the compressor died.

Thanks for any and all advice!

 

[alldodge]

Both fans should turn easy, the one not turning has an issue and should be replaced/repaired.

The extra radiator fan is needed to help draw the heat away from the condenser coil and radiator. Don't think you have an compressor issue because it would start squealing. Now if you smelled not rubber but antifreeze, there could be a heater core issue

The burnt smell in the carb was not coming from the radiator fans. Could be the interior fan has an issue. The heat and A/C use the same interior fan, turn the heat on and move the fan speed up and down and see if you smell the burning.

 

[sublauxation]

More or less what I was thinking, thanks! By turn easy I'm guessing you also mean turn relatively quietly? Both squeak a bit but the condenser fan is a constant groan.

We had a lot of thick Canadian fire smoke coming down at that time and it may have made the smoke smell worst than it really was. It definitely wasn't antifreeze, it smelled more like a hot electrical wire or plastic melting.

I don't think it's a problem with the blower fan because we kept the vent blowing and had no problems after shutting off the AC. I checked every fuse associated with the AC that I could find and all were good. I'll probably replace the AC clutch relay just because it's cheap. I'm banking on the fan being the only problem, or at least hoping.

I'll check theAny other thoughts on what else to check?

 

[sam am I]

I was thinking that since the cold stopped "abruptly", It's the compressor?

I'd guess a fan crapping the sheets would smell perhaps but not "abruptly" stop the cold but, would only "effect" the cold by increasing the temp a bit and a half or twelve. My money is on the compressor (the electro mag clutch burnt up and stop engaging the pump) and the fans are probably just worn but both work still.

If and when the electro clutch went out, it may have also blown a seal and you lost all the ice cube juice as well. You'll find that stuff right next to the blinker fluid at your local Auto Zone. :]

 

[alldodge]

Using blend air which some air flow comes outside, you could be smelling the AC fan burning up. The fan should not squeak and should be quite when turned. Sounding to me more like it's just the fan

 

[sam am I]

You could be right Dodge, I'm just guessing with the sudden cold to not cold. And agreed, the normal good fan shouldn't squeak and spins freely.

 

[mla2ofus]

I'd say with abrupt temp change, if it's a vacuum actuated mixer door something could have happened to make it turn off the cold air and just let in outside air. If you lost the compressor clutch there would be a gradual warm up over a minute or so. If the condensor fan quit the engine might start running warmer.
JMHO,
Mike

 

[sublauxation]

Keep the JMHO's coming!

I just went out and let it run for 10 minutes, nothing bad happened. Air blows out of the vents with no problems and no smells. I took off the Serpentine belt and played with the Compressor pulley and it seems fine.

Then I got brave and turned on the AC. It worked just fine. I let it run for about 3 or 4 minutes and nothing bad or unusual happened. The electric Condenser fan definitely sounded a bit loud. Maybe I should have left it run longer but I didn't want to break anything. Once I turned it off I spun the condenser fan and it definitely squeaked pretty loudly when turned by hand.

Which brings up the question, if it was the compressor clutch would it be all or nothing or can it fail gradually?

I hate throwing $150 into the condenser fan but it looks to be a pretty quick job and seems likely to be bad even if it isn't the whole problem. I'm afraid if I bring it in I'm getting a new compressor regardless of the actual problem as it seems many shops diagnose by replacing parts, and they often start with the most expensive.

Thanks for any and all further info!

 

[sam am I]

Dollar still says its the compressor.........Guessing the thermal protector integral to the compressor shut off the compressor. Takes maybe 30/45 sec's (depends on ambient of course) and warm air would start to blow once the switch stays opens.

Again guessing that perhaps your compressor is starting to fail and is overheating (the burning smell), the thermal switch is opening when it over heated but, now has closed since its cooled down.

When you use the term "abrupt"......do you mean like milliseconds or like around a minute?

Just a guess of course without being personally under the hood ya know.

 

[sublauxation]

Not exactly sure of the exact time frame of when it stopped but it was working when we left the house and we drove only about 2 miles. My wife said something about the AC not working and it was about 10 or 20 seconds after that that we noticed the burning smell.

What would cause it to overheat? Bad bearings? I don't know much about these but the first research wasn't good as the Ford Bulletin says if the compressor goes you have to replace basically the entire system including all the hoses due to metal shaving contamination. I don't want that! I suspect/hope that since it just ran fine for a couple minutes that I haven't reached that catastrophic point, and that's why I'm reluctant to just change out the condenser fan.

 

[sam am I]

Sure, a bearing going out could cause overheating as well as low refrigerant and/or low lubricant flow can make them overheat too!!

If the fan is flaky, that might do it too, probably more noticeable at low speeds thou.

Sorry to say, really it's just guess work until something really breaks or you take it into a trustworthy mech that can do some diagnostics with gauges and such. Or.........

I'd guess there are few folks here that do auto ac for a living that might be able to walk through some more detailed DYI tests perhaps. I just messed with a few over the years and actually have installed only 1 entire system in my GF's Honda last summer, so I just know enough to be dangerous. Got all the parts (space heaters not included) from a wrecked Honda for cheeeeeeeep!!



It actually is still cooling super coooooold too...........amazing!!!

 

[alldodge]

If you were driving down the expressway above 50 mph you don't need the fan. So if the fan stopped working and you smelled smoke, it should still be cooling. Now if you were easing down the road and the fan stops, there may not be enough air flowing over the condenser, and if its dirty would cause more reduction of capacity.

Agree if compressor blew up (inside) then the systems has to be cleaned out.

I'm still with the fan until more evidence.

 

[sam am I]

I think he was driving down the expressway more or less Dodge and it still quit cooling with plenty of air flow, like ya said, no fan needed.........That's why I figure compressor dropped out. Who knows thou at this point.....I just catch skunks these days anyway

 

[sublauxation]

I drove about 3 or 4 miles at no more than 30 mph. We set a record temp and it was about 91 degrees out when it happened. When I checked the AC yesterday the condenser fan and the radiator fan both kick in as soon as the AC is turned on making me think it runs constantly if the AC is on, but I could be wrong.

That brings up another question though, I'm not sure if the fans come with a new fan control module. I'll call tomorrow to verify that. I've done a little more reading and it sounds like the module can go wonky and will only run at half speed, meaning you wouldn't necessarily notice it's not working correctly.

I've read a lot of complaints about Ford Explorers and both cooling fans crapping out which makes me wonder if this is the reason they have so many compressor problems, with people repeatedly overheating them because they don't realize the fans are going bad. Neither fan to me feels like they spin the way they should.

I'll order the fan tomorrow and hopefully know more this weekend when I swap it out, but I'm thinking about also setting up an AC system check once I'm done just to be sure. I read online that Pep Boys Auto Parts stores will do a free quick check with gauges which would be worthwhile.

 

[alldodge]

Most AC fans turn on and stay on while the AC is running.

As for someone checking the AC, IMO that's not necessarily a good idea. The reason I say this, is the person plugs lines on your system which are full of air. When connected they take a small amount of Freon out of your system to fill the lines. If all checks out, you now have less Freon in the system then before.

To make matters worst is if you do need some Freon, they add some along with the compressed air that was in the lines. If they would have purged their lines with Freon before connecting this would be offset.

 

[sublauxation]

Fan will be here next week so I'll start there, I spun it again today and it seems louder than yesterday, maybe that's hopeful thinking.

Would you bother having somebody check out the whole system afterwards or just run it and be sure to turn it off immediately if it stops cooling again?

 

[bruceb58]

Most AC fans turn on and stay on while the AC is running.

As for someone checking the AC, IMO that's not necessarily a good idea. The reason I say this, is the person plugs lines on your system which are full of air. When connected they take a small amount of Freon out of your system to fill the lines. If all checks out, you now have less Freon in the system then before.

To make matters worst is if you do need some Freon, they add some along with the compressed air that was in the lines. If they would have purged their lines with Freon before connecting this would be offset.

That is why you always purge the line before filling.

This is a good read on how to minimize refrigerant loss when using gauges.
http://autoacforum.com/messageview.c...threadid=29761

 

[bruceb58]

Again guessing that perhaps your compressor is starting to fail and is overheating (the burning smell), the thermal switch is opening when it over heated but, now has closed since its cooled down.

I have never seen an automotive AC compressor that has a thermal switch. The AC compressor has wires going to the compressor clutch and that's it.

 

[alldodge]

That is why you always purge the line before filling.

I know, he mentioned pepboys,

 

[bruceb58]

I know, he mentioned pepboys,

Who mentioned pepboys?