A/c cuts out above 90 mph ?
 

Air conditioner cuts out above 90 mph,
starts working after slowing down?

I have to wonder, are you really concerned about the AC at 90mph? Do you normally cruise at 90mph and get frustrated that it's not nice and cool?

If I was going that fast, I'd want the AC to shut off to free up power, and release the load of the A/C on the cooling system.

Just drive at 89 mph.

Yes I cruise at 85 to 90 all the time, with cruise control on most of the time!
Last week driving through the big valley it was 107*F so yes A/C On!!

Eng Temps were Fine .
Six gear cruising Along

I don't know about that. Every time I get up to 88 mph, I see some serious shit.
http://38.media.tumblr.com/tumblr_m9...8bp2o1_500.gif

What valley do you call the "big valley" ...... ??

The A/C compressor will cut off under extreme load ........ maybe, at those speeds, the engine considers itself under extreme load ....... :iono:


humfrz

Do you know if that's vacuum or RPM based?

Calculated engine load v. user demand.

Open the window, this will do three things:

1. Cool the cabin down.
2. Generate increased cabin noise.
3. Cause the cars drag coefficient to increase slowing it down allowing the air A/C to come back on.

lol you know California's Central Valley. Not much has changed since you first visited I'd wager.

http://www.islandbreath.org/2009Year...11dustbowl.jpg

Interesting to hear it shuts off at 90, I could see that happening going up a hill (due to high load as mentioned before) but surprised it happens on flat level roads. Maybe dropping down to 5th will reduce the load via gearing and allow you to stay cool?

You've never driven in 110 degree heat have you?

Yes, but I was having some fun, suggesting dropping below 90 is mundane.

Could it be the 110 Degree heat being forced in via high pressure area where the cabin intake is and overwhelming the evaporator?

Try turning on cabin recirculate to shutout air from the outside. Otherwise it's possibly the ECU turning off the AC unit due to load/demand.

Eh, couldn't verify if my car does this. I have very few opportunities to go more than 90 on the interstate, and in those rare situations, someone usually slows me down sooner rather than later.

If it has happened to me, the cabin would have already been cold, so I probably never realized it was happening.

:iono:

but, I would guess vacuum based.


humfrz

It seems to me the A/C cuts out at particular throttle settings regardless of actual load (of course I could be wrong here).

I haven't monitored the actual throttle percentage at where this seems to occur (data is available on OBD Fusion when connected to the A Network through a Carista reader) but I would guess it's around 85-90% of throttle travel.

The effect on the A/C in those circumstances is like a light switch. Running the system on recirculate does help moderate the effect, but there's not enough Squash air freshener in the world to solve what happens when you run it that way for a long time... even with a fresh cabin filter.

Oh I think it has changed a lot since Hum was there the first time.


http://jan.ucc.nau.edu/rcb7/MidCretpalgeo.jpg

Ahhh ....... The Central Valley ......most likely he was cruising on a portion of I-5.

Back-in-the-day, we called that stretch of I-5 the West Side Freeway.

I remember, back when I was roaming the Central Valley, getting on the uncompleted portion of I-5 off of 152 near Los Banos, and roaring down the west side at over 100 mph and jumping off at Lost Hills, just north of where the freeway ended.

How could I go 100 mph..?? There was virtually no traffic, because the freeway ended in the middle of nowhere, so very few people took it. Secondly, it wasn't patrolled, because there was no traffic......:D


humfrz

I would regularly run 120-130 in fairly tight "caravans" of slightly fast cars (factory supercharged and tuned MR2 MK1 at that time) on that stretch when I lived in LA and would drive to Sacramento or the bay area. Had to slow way down in places like Stockton but there were plenty of spots where you could drop the go-fast button right to the floor.

Wouldn't think it's JUST the 110 heat...Here in phoenix it hits 110 a few times a year and I've never had the AC go out during normal traffic speeds.

Central Valley = Big Valley
Lots of fast cruising if you pay attention to the overpass , day light only,
and use WAZE!!!!
Am heading back next week LA to Napa
Will try in Recec mode
All so try 5th and 6th to check throttle position for changes
Thanks For the Help
Paul

Just guessing but ecu likely controls a\c like it does the alternator . With alternator it will stop charging unler highh acceleration ( may not of battery\volts low) so it likely a\c is controled in similar way.

Now how the ecu does this is unknown ie is it a combination of speed, engine load rpm coolant or oil temps throttle position for a certian time period who knows. But if it consistetly drops out at certian times it lilely the ecu doing its thing but it may not be based on a single parameter more likely based on several conditions being tripped

Its normal, AC will cut under full throtle, at any speed. Like it wont shut down, but the compressor wont work until you let off some. Gotta choose between ponies or cool air :) (you might try not going wot for a few seconds at a time to keep the air cool enough).

Sorry, I implied the faster speed causing an even higher than normal high pressure on the cabin intake with the combination of high heat. I wasn't so clear in my reply.

Interesting use case. If I usually cruised at 90mph, I think I would of opted for a bigger displacement engine.

Ah okay. I definitely didn't catch that xD

It's a safety feature designed to reduce compressor freeze/wear issues. The A/C compressor as you know is on a parasitic pulley that can shut off. But it's not designed to operate at high speeds for long durations, and all cars are optimized for the mass market, which typically doesn't cruise over 90.

My car does the same thing, if you want to adjust it I wouldn't be surprised if you can in techstream via OBD II. Freeze shouldn't be an issue when it's 110°, but wear on the compressor will still be higher at high RPM.