Took a trip to the mountains this weekend and noticed my AC starting to act up. Climate control on MAX, fan on second setting. As I climbed up the mountain the AC would almost quit. The air warmed considerably and the blower felt it was less than on 'low'. As soon as we leveled out again, (no climb) the AC would start blowing again like it should (cold and with force). My passenger thought it was a 'vacumm' problem. Thanks for any insight before I take to the dealer.

1996 F250HD 5.8L 70,000 miles. John

 

I think your passenger is right about the vacuum problem. I've seen this happen before. You need to check all the vacuum lines for cracks and make sure they are hooked up properly and make sure you check them under the dash as well.

Les

 

Not sure about this era of vehicle, but the older ones would cut off the AC when you downshifted. Explanation was that if you needed the extra power to cause a downshift, that it'd help to cut the AC too. Of course, that's just the old shadetree guys talking, but it seemed like a decent explanation at the time.

 

>Took a trip to the mountains this weekend and noticed my AC
>starting to act up. Climate control on MAX, fan on second
>setting. As I climbed up the mountain the AC would almost
>quit. The air warmed considerably and the blower felt it was
>less than on 'low'. As soon as we leveled out again, (no
>climb) the AC would start blowing again like it should (cold
>and with force). My passenger thought it was a 'vacumm'
>problem. Thanks for any insight before I take to the dealer.

Most cars these days, and certainly my 4.6l '96 t-bird/'97 cougar
plus my '01 F250 SB SC do shut off the A/C compressor clutch
under high loads. Recently, with my t-bird loaded with wife/kids
and full trunk plus a 900 lbs trailer, climbing a "hill" in upstate
New York, the A/C gave up quite early. I did NOT have my foot to
the floor. Even with a 3.73 rear, the lack of performance and room
immediately made me go out and buy an '01 F-250 V10

In the 80's, this was done at WOT (wide-open-throttle) but these
days, it seems whenever the computer decides it would be better
(cleaner), it shuts off the A/C clutch.

In the 70's some cars (my Triumph TR7's come to mind) had a WOT
switch to kill the current to the A/C clutch.

Sounds like you're hitting the computer's idea of when to shut
off the A/C. You didn't mention if you were fully or even moderately
loaded. Steep grade?

art k.

 

>>Took a trip to the mountains this weekend and noticed my AC
>>starting to act up. Climate control on MAX, fan on second
>>setting. As I climbed up the mountain the AC would almost
>>quit. The air warmed considerably and the blower felt it was
>>less than on 'low'. As soon as we leveled out again, (no
>>climb) the AC would start blowing again like it should (cold
>>and with force). My passenger thought it was a 'vacumm'
>>problem. Thanks for any insight before I take to the dealer.
>>Sounds like you're hitting the computer's idea of when to
>shut
>off the A/C. You didn't mention if you were fully or even
>moderately
>loaded. Steep grade?
>
>art k.

Thanks Art, and everyone. Sorry it took so long to get back here, we went to the beach. No, not even moderately loaded this trip. I have used this truck to haul a three horse slant, loaded, without the AC acting up. The steepest grade is 6% for 7 miles, but this trip the ac would quit working normally even under a slight rise, 2...3% for a short distance of a mile or so. The funny thing is that it not just blowing warmer air, but also the volume via the fan declines significantly. Thanks, John

 

Its the vacumne(sp)line in the right front fender area.I have fixed two of my buddies trucks.Plastic line cracks or gets pinched.Find the crack or break and mend with a piece of rubber vac. line,Mark