recirculation mode makes ac last longer?

[The motor guy]

So I recently learned that dodge ram trucks eat compressors and evaporator cores frequently. Well I noticed from day one the ac kind of sucks when you leave it on fresh air mode. It would quit blowing cold periodically in traffic and the engine fan would come on almost every other time when leaving from a stop, so I just left it on recirc mode which stopped this problem. I also when I remembered would turn the compressor off and leave the fan on for the last minute or so to help blow the moisture out of the system at the end of a drive. My ac lasted 10 years almost doing this. My main concern was going through fan clutches having it lock up all the time.

Opinions?

 

[901Memphis]

I try not to worry about stuff before it breaks. Fix stuff as it needs fixing, as it gives you warning signs and stop worrying so much

 

[SZR48207]

Recirc mode doesn't have to cool air that is "outside hot", so assuming the HVAC system cools to a specific point, then the delta temp would be less on recirc mode. Less delta temp means compressor doesn't need to cycle on as much?

And +1 on turning off AC and letting it blow as vent for a minute or two before arriving at home/work each day. Drying out the evap coil helps prevent it from getting all mildewy and smelly.

 

[901Memphis]

I just leave it on high, because the wear and tear on the switches are a more likely failure point imho

 

[merconvvv]

"I just leave it on high, because the wear and tear on the switches are a more likely failure point imho"

So true on dodge chrysler. The ac panel push buttons caused my panel to malfunction which by default will turn on the blower at highest speed with hot air coming out of defrost vents. Not fun and even a pain to diagnose. Used unit from ebay fixed it on my 94 concorde. That 3.3 rocks though.

 

[The motor guy]

Oh I didn't touch the knobs, just the one button. I find it hard to believe that would wear out.

 

[The motor guy]

Originally Posted By: 901Memphis
I try not to worry about stuff before it breaks. Fix stuff as it needs fixing, as it gives you warning signs and stop worrying so much

You are not a true BITOG then!

 

[alex_at]

turning the ac off to "dry" it before stopping: Exactly that behaviour made my system stink. My mechanic told me to keep the AC on all the time - since I do that no more stink.

 

[artbuc]

Originally Posted By: Reddy45
Recirc mode doesn't have to cool air that is "outside hot", so assuming the HVAC system cools to a specific point, then the delta temp would be less on recirc mode. Less delta temp means compressor doesn't need to cycle on as much?


Think it is the opposite. Fresh air will require constant ac operation whereas recirc will substantially reduce cooling load which will require compressor to cycle more frequently due to shorter run times. Recirc will improve mileage and possibly keep cabin cooler but it will be harder on compressor clutch.

 

[Ethan1]

That's exactly what Reddy45 said

 

[Kestas]

Not just less delta T, but in recirc mode the a/c doesn't need to squeeze the moisture out of the air before lowering the temperatures. Dehumidifying the air takes a lot of energy.

 

[CharBaby]

I think that the recirc mode(which closed off the damper to the outside) may help reduce the amount that the A/C need to operate and keep the interior cool but, this is dependent on driver & passengers.

However, those who may not know, you want to circulate the A/C's cool inside air and NOT try to cool the hot air that is coming into the cabin from the outside.

But, IDK if the recirc mode makes the system last any longer. Maybe statistically! Personally I have had vehicles that had the same unrepaired A/C systems for over 20 years and others that needed repairs as soon as 3 years. Any A/C failures that I have occured over the life of any vehicles I've owned for any length of time were typically caused by...

...rusted condenser or "L"/"H" A/C lines, deteriorating O-rings/seals or other non related issues that had nothing to do with the recirculation mode in the dash switch/function.

 

[Jetronic]

Originally Posted By: artbuc
Fresh air will require constant ac operation whereas recirc will substantially reduce cooling load which will require compressor to cycle more frequently due to shorter run times. Recirc will improve mileage and possibly keep cabin cooler but it will be harder on compressor clutch.

not an issue with todays variable displacement compressors

 

[Jetronic]

Originally Posted By: Kestas
Not just less delta T, but in recirc mode the a/c doesn't need to squeeze the moisture out of the air before lowering the temperatures. Dehumidifying the air takes a lot of energy.


That's what I want most from my AC: dehumidiying. I chose an interior temp a few degrees below outside (if really hot) or the same, and let the AC dry the air. That way I'm comfortable and don't get h&ammered from the temperature difference when iopening a door or window.

 

[KrisZ]

There is nothing you can do about the compressor cycling and clutches engaging/disengaging, the system controls that.

On my Mazda 3, which has a marginal AC, I have to use the recirc pretty much all the time, otherwise it performed even worse. My minivan, on the other hand, I hardly ever use the recirc function, the system has absolutely no trouble keeping the interior cool, which is a good thing because having six people in there and recirc on, would get the air stale mighty quick.

 

[HerrStig]

I've got a '99 Camry with 350,000 miles, running the AC about half the year. The AC has required nothing in that time but a R 134a top off. Perhaps running the recirc might make it last to what, 500? I suspect the parts quality is pretty good in that Generation Toyota. One cooling fan on these cars runs constantly when the AC is engaged, recirc or not, the compressor, of course, cycles less with the recirc engaged.

 

[Rand]

Originally Posted By: Jetronic
not an issue with todays variable displacement compressors


except many cars dont use em... even the same car manufacturer uses different types.

 

[Jetronic]

They have become standard issue in europe, starting a decade ago. You'd have a hard time sourcing a new car with a fixed displacement compressor.

 

[E150GT]

This is an interesting subject. I think the important thing is to use the ac. Keeps things oiled. Next, is keep the condenser clean. Dirty condenser causes higher pressure and more wear on the compressor.

 

[nicholas]

Re-circulation - allows the AC compressor to run at a lower PSI.

I noticed this on every car we have had. Cooler air in the cabin to remove the humidity from.