A/C Stops Working Going Uphill

[yooteeayud]

I have a 2008 Sport Trac XLT which has never given me any problems, however lately I have noticed that whenever I am going up a hill, or have the engine 'under load', the air conditioner will stop working until I top the hill or release the load on the engine, by taking my foot off the accelerator. I never noticed this before, so I don't know if this is normal or not. Any ideas would be appreciated.

 

[Jon94]

How hard are you stepping on the gas? Explorers, and probably most other cars, have a relay or a sensor that automatically shuts the compressor off under WOT to give the engine more power. I don't know if you have to actually have it floored to trip it. It may trip under heavy load/acceleration even if it's not totally floored.

 

[Maniak]

Is it really turning "off" the a/c, or is it just that the air is now coming out the defrost vents? When the vacuum ball/check valve goes bad the air moves to the defrost vents when the engine looses vacuum (heavy load).

~Mark

 

[yooteeayud]

How hard are you stepping on the gas? Explorers, and probably most other cars, have a relay or a sensor that automatically shuts the compressor off under WOT to give the engine more power. I don't know if you have to actually have it floored to trip it. It may trip under heavy load/acceleration even if it's not totally floored.

I don't have to 'floor it' to get the a/c to shut down...just going up a regular hill (in East Tennessee...) will cause the a/c to stop working. No air comes out any vents until I get to the top of the hill and take my foot off the accelerator pedal. Once I take my foot off the accelerator then the a/c returns to normal.

 

[yooteeayud]

Is it really turning "off" the a/c, or is it just that the air is now coming out the defrost vents? When the vacuum ball/check valve goes bad the air moves to the defrost vents when the engine looses vacuum (heavy load).

~Mark

Hey Mark...No air at all out of ANY vents. It's almost like a vacuum leak, or maybe a pinhole in the control valve. Once I remove my foot from the accelerator, everything reverts to normal. Perhaps it has done it all along (and is normal), but I just began to notice it a week or so ago, so thought I'd ask.

 

[Sedition]

My truck is doing the exact same thing but its getting worse. Did you ever solve it?

 

[djmunster]

So does mine , and I have no clue why

 

[pdsmith2180]

AC changes when going uphill

My ac starts coming out of the defroster vents then when I am off the hill it goes back to normal. I see that it was mentioned that the Vacuum ball / check valve goes bad. Is this correct?

 

[Maniak]

My ac starts coming out of the defroster vents then when I am off the hill it goes back to normal. I see that it was mentioned that the Vacuum ball / check valve goes bad. Is this correct?

Yup.. You loose engine vacuum when going up hill and the check valve is supposed to keep the vacuum in the system. Without it your relying on the vacuum you are getting from the engine which isn't there when your going uphill.

~Mark

 

[Mike764]

In addition to the check valve, a small leak in the vacuum circuit can cause this. I had one due to a cracked vacuum line at the vacuum reservoir.

 

[eds01lightning]

Anyone have a pic of this vacuum check valve and an exact location? My 08 ST is doing the same thing going up hills/accelerating. A part number would help as well.

 

[Col]

Anyone knows where is located the vacuum check valve in a 2004 exp??.. Thanks

 

[cire0809]

if its the same problem i have in my 2000 ford ranger the check valve inside the vacuum ball has gone bad. Just buy a generic check valve from the auto parts store and isolate the engine from the vacuum ball(Suck on the valve and find out which side "checks" the vacuum), it solved my problem completely.