AC...Low Side and High Side


polarzak
05-24-2010, 04:33 PM
My daughter's 2003 Grand Am seems to need a charge of 134a. The compressor is running all the time, not cycling, but the air in the cabin in only slightly cooler than outside air. There is pressure in the system. In my younger years, and the days of R12, the larger AC line was the low side, the thin line was the high pressure side. I suspect the basic principles of AC have not changed.

On her car, there is a thin line in the front just behind the rad/condensor, and valve is large, and fits my charge (low side) fitting, but I think it is the high pressure line. However, near the firewall, (Evaporator) is the larger line (but a small service valve)that I would expect the be the suction, however the valve is small, and will not fit my gauges and fittings.

Any help would be appreciated. Thank you.

doctorhrdware
05-24-2010, 05:58 PM
You need to go to an auto zone or any other auto parts store and get the quick connect valves for the air condition system. The low side is the small connection on the system and the large connection is the high side of the system.

brcidd
05-24-2010, 09:31 PM
Variable stroke compressors never cycle- by design--

polarzak
05-25-2010, 05:34 AM
You need to go to an auto zone or any other auto parts store and get the quick connect valves for the air condition system. The low side is the small connection on the system and the large connection is the high side of the system.

Thanks for the confirmation and suggestion.

ricebike
05-25-2010, 11:42 AM
i think doc is wrong here...

2003 already has the R134A system quick connect valves on the vehicle, most manufactured vehicles in the US had this starting 1995 because the R134A connections that i've seen on a 1995 honda accord, 1997 chevy cavalier, 2002 nissan quest, 2005 acura mdx, etc all can take the same charge hose that i got from walmart

http://www.2carpros.com/forum/automotive_pictures/12900_ac_service_fittings_28.jpg

it usually has a plastic blue dust cap with an "L" stamped on it

the following pic is for illustration purposes only:

http://milkyourmoney.com/wp-content/uploads/2009/05/low.jpg

but on the honda and nissan, they have black caps, but still has the "L" stamped on it to verify that it's the low side for the R134A charge kit to hook up

http://www.gaownersclub.com/forum/showthread.php?t=108791

http://www.gaownersclub.com/forum/showthread.php?t=126267

maybe that link to the grand am owners club can help <shrugs>

doctorhrdware
05-25-2010, 02:41 PM
Ricebike
Thank you for the great illistration on the different ac system connections for the car.

polarzak
05-25-2010, 03:35 PM
I just need confirmation of where the low side was as Ricebike is correct, daughter's car has the 13 mm quick connect. BUT, it still have a problem....my quick disconnect 13mm connector is too shallow to click on to the service port. The port seems to be too high in the Gran AM because it fits fine on my Buick Lucerne and the wife's Lacrosse.
Are Grand AMs different?

Thanks again for the help.

doctorhrdware
05-25-2010, 04:09 PM
i think doc is wrong here...

2003 already has the R134A system quick connect valves on the vehicle, most manufactured vehicles in the US had this starting 1995 because the R134A connections that I've seen on a 1995 Honda accord, 1997 Chevy cavalier, 2002 Nissan quest, 2005 Accra mdx, etc all can take the same charge hose that i got from Walmart

http://www.2carpros.com/forum/automotive_pictures/12900_ac_service_fittings_28.jpg

it usually has a plastic blue dust cap with an "L" stamped on it

the following pic is for illustration purposes only:

http://milkyourmoney.com/wp-content/uploads/2009/05/low.jpg

but on the Honda and Nissan, they have black caps, but still has the "L" stamped on it to verify that it's the low side for the R134A charge kit to hook up

http://www.gaownersclub.com/forum/showthread.php?t=108791

http://www.gaownersclub.com/forum/showthread.php?t=126267

maybe that link to the grand am owners club can help <shrugs>

I stated that the low side is the smaller quick connect and the larger quick connect is the high side. Since I did not know the sizes of the actual service ports, I used large and small to describe the service ports. I have a 97 GP SE and the connections are the large port is the high side and the smaller connection is the low side. The AC service gauges that I have for 134A , there are 2 quick connect fittings one is red which is the high side which is the large connection on the AC system. The other quick connect connection is blue which is the small service port.

I am not sure if the Grand AM is different or not. But with GM anything is possible. I would guess that is should be the same for most if not all GM models.:2cents:

polarzak
05-25-2010, 04:45 PM
I think I may have confused things with my last post. I know which one is the high and low side now..but the problem is the smaller 13mm low side is about 1/8 higher than the one on my Lucerne and Lacross and so my gauge connector is too shallow to snap on to it. You are right however, anything is possible with GM.

Years ago the low side was right on the dryer and easily accessible, now one has to have the hands of a kid to fit in the area. Anyway, thanks much for your help.

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