A/C problems...perhaps

Hi folks, hope you all had a great weekend.
My wife and I just returned from a 200 mile trip in our 98, 5.0 AWD. It was
brought to my attention by my wife that the A/C blower was slowing down when
I accelerated or went up a gradual incline, I hadn't noticed it before she
brought it to my attention. The blower switch was on the next to highest
setting all during the trip, also the rear seat blower was on.. The problem
occured in either A/C or A/C MAX. The temperature was in the low 90's, 60%
humidity and the dewpoint was around 70.
Do any of you have any idea what is causing this problem?
Thanks to all,
Steve

"Ashton Crusher" > wrote in message
...
> On Sun, 8 Jul 2007 19:17:35 -0400, "Esteban" >
> wrote:
>
> >Hi folks, hope you all had a great weekend.
> >My wife and I just returned from a 200 mile trip in our 98, 5.0 AWD. It
was
> >brought to my attention by my wife that the A/C blower was slowing down
when
> >I accelerated or went up a gradual incline, I hadn't noticed it before
she
> >brought it to my attention. The blower switch was on the next to highest
> >setting all during the trip, also the rear seat blower was on.. The
problem
> >occured in either A/C or A/C MAX. The temperature was in the low 90's,
60%
> >humidity and the dewpoint was around 70.
> >Do any of you have any idea what is causing this problem?
> >Thanks to all,
> >Steve
> >
>
> Sounds like a vacuum leak problem. It sounds like the blower is
> slowing down because the various vacuum controlled doors are starting
> to move to their un powered positions when you go uphill and the
> vacuum from the engine drops. That makes the air start to go out of
> places under the dash instead of the dash vents and that makes it seem
> like the blower is slowing down. It could be you have a bad check
> valve, they are usually under the hood in the main vacuum line to the
> AC system, you could have a cracked vacuum canister/reservoir, or you
> could have a vacuum leak in a vacuum line under the dash or in one of
> the vacuum motors. Those are my guesses.

Thanks Ashton. My '78 F350 does that. The fan sometimes shuts off
completely when going uphill etc. I'm off to check my hoses and check
valves now.

Thanks Ashton,
I have set aside most of my upcoming weekend to check for vacuume leaks and
bad lines. Groan!<G>
Steve


"Ulysses" /> wrote in message
...
>
> "Ashton Crusher" > wrote in message
> ...
>> On Sun, 8 Jul 2007 19:17:35 -0400, "Esteban" >
>> wrote:
>>
>> >Hi folks, hope you all had a great weekend.
>> >My wife and I just returned from a 200 mile trip in our 98, 5.0 AWD. It
> was
>> >brought to my attention by my wife that the A/C blower was slowing down
> when
>> >I accelerated or went up a gradual incline, I hadn't noticed it before
> she
>> >brought it to my attention. The blower switch was on the next to
>> >highest
>> >setting all during the trip, also the rear seat blower was on.. The
> problem
>> >occured in either A/C or A/C MAX. The temperature was in the low 90's,
> 60%
>> >humidity and the dewpoint was around 70.
>> >Do any of you have any idea what is causing this problem?
>> >Thanks to all,
>> >Steve
>> >
>>
>> Sounds like a vacuum leak problem. It sounds like the blower is
>> slowing down because the various vacuum controlled doors are starting
>> to move to their un powered positions when you go uphill and the
>> vacuum from the engine drops. That makes the air start to go out of
>> places under the dash instead of the dash vents and that makes it seem
>> like the blower is slowing down. It could be you have a bad check
>> valve, they are usually under the hood in the main vacuum line to the
>> AC system, you could have a cracked vacuum canister/reservoir, or you
>> could have a vacuum leak in a vacuum line under the dash or in one of
>> the vacuum motors. Those are my guesses.
>
> Thanks Ashton. My '78 F350 does that. The fan sometimes shuts off
> completely when going uphill etc. I'm off to check my hoses and check
> valves now.
>
>
>