Air conditioner compressor cycling too often?

2000 Chev Express van, 5.7 litre gas, front air only (rear air leaked and we
just blocked off the whole rear section with caps and refilled the system).
The compressor is noisy - but it always was noticable. It cycles on and off
incessantly, exactly 6 seconds on, 4 seconds off. Problem is worse when the
truck is under load (towing) and I am running in third gear at normal
highway speeds so higher than normal RPM.

Any ideas? Air is cold, so it's working - but it sure doesn't seem normal.
It seems to load the engine a lot as well, but that's probably my
imagination.

Thanks, Brian

Brian wrote:
> 2000 Chev Express van, 5.7 litre gas, front air only (rear air leaked and we
> just blocked off the whole rear section with caps and refilled the system).
> The compressor is noisy - but it always was noticable. It cycles on and off
> incessantly, exactly 6 seconds on, 4 seconds off. Problem is worse when the
> truck is under load (towing) and I am running in third gear at normal
> highway speeds so higher than normal RPM.
>
> Any ideas? Air is cold, so it's working - but it sure doesn't seem normal.
> It seems to load the engine a lot as well, but that's probably my
> imagination.
>
> Thanks, Brian

I'm thinking back to my two cars, and they both seem to cycle on for
about 6 seconds or so on a steamy summer day in the mid-atlantic
states.

As I remember the old style GM AC compressor would stay on consantly,
but AFAIK that model isn't used any more.

You said the problem is worse when under a load, but I wasn't sure what
you meant by worse. Are the cycles of shorter duration? Or is it just
more noticable because the engine bogs a bit when the compressor kicks
in.

If I am driving under unloaded conditions - just cruising at 70 mph empty -
the compressor cycles the same but is quieter. If higher rpm's it's
noticably louder..

Brian

"John S." > wrote in message
oups.com...
>
>
> Brian wrote:
>> 2000 Chev Express van, 5.7 litre gas, front air only (rear air leaked and
>> we
>> just blocked off the whole rear section with caps and refilled the
>> system).
>> The compressor is noisy - but it always was noticable. It cycles on and
>> off
>> incessantly, exactly 6 seconds on, 4 seconds off. Problem is worse when
>> the
>> truck is under load (towing) and I am running in third gear at normal
>> highway speeds so higher than normal RPM.
>>
>> Any ideas? Air is cold, so it's working - but it sure doesn't seem
>> normal.
>> It seems to load the engine a lot as well, but that's probably my
>> imagination.
>>
>> Thanks, Brian
>
> I'm thinking back to my two cars, and they both seem to cycle on for
> about 6 seconds or so on a steamy summer day in the mid-atlantic
> states.
>
> As I remember the old style GM AC compressor would stay on consantly,
> but AFAIK that model isn't used any more.
>
> You said the problem is worse when under a load, but I wasn't sure what
> you meant by worse. Are the cycles of shorter duration? Or is it just
> more noticable because the engine bogs a bit when the compressor kicks
> in.
>

If it is a noisy compressor to begin with, as some compressors are, it
probably will sound even noiser at higher rpms.

On Tue, 19 Jul 2005 14:09:15 -0400, "Brian" >
wrote:

>2000 Chev Express van, 5.7 litre gas, front air only (rear air leaked and we
>just blocked off the whole rear section with caps and refilled the system).
>The compressor is noisy - but it always was noticable. It cycles on and off
>incessantly, exactly 6 seconds on, 4 seconds off. Problem is worse when the
>truck is under load (towing) and I am running in third gear at normal
>highway speeds so higher than normal RPM.
>
>Any ideas? Air is cold, so it's working - but it sure doesn't seem normal.
>It seems to load the engine a lot as well, but that's probably my
>imagination.
>
>Thanks, Brian
>

You are probably low on 134a. The low pressure switch turns the
compressor off when it gets down to "X" psi. Once the compressor cuts
off the pressures raises back up over "X" psi so the system turns back
on. While I would reccomend having the low and high pressure sides
checked to see how the charge is doing you can pick up one of those
cans of 134a with the low pressure gauge built right on the can. They
aren't the most accurate things in the world but will at least give
you a clue if you are cutting off on low pressure.

Steve B.