Air Conditioning Trouble Shooting.

[DannMann99]

I have a 96 Buick PA, it has been running surprisingly well with 75k miles on it. My AC has not worked for the past year or so...

I was wondering if maybe you guys can help me trouble shoot this and maybe find out what's wrong and if I can do anything for it myself or will i just have to take it to a mechanic and let him figure it out...

The AC worked fine the year prior, came out cool, never had any hiccups or any other events, I never noticed the quality of cold air decreasing either... This past summer though when I first tried to use it it did not produce any cold air whatsoever. Would just blow fan air, despite what settings/etc I toyed with. No noises or other oddities noted when I turn the AC on either.

The heater works fine, both never blew any air out of the main vents ( never figured out why nor cared) but they would blow hot/cold air out of the defrost and floor vents (which is fine)...

Maybe you guys can point me in a good direction to go with this. Trying to keep it cheap. I casually talked to a mechanic about it a year ago and he mentioned some electronic setup that is probably bad... (mentioned it costing a few hundred) Not sure if he was trying to hose me and I never really followed up with it, but now that it's getting warmer I'm trying to fix this early.

[MagicRat]

AC on older cars often fails. In my experience, old components, (hoses, o-rings, seals etc) inevitably allow the coolant (freon or R-134A) to leak out.

The system has a pressure switch. When it senses low or no freon pressure, it prevents the AC compressor from engaging, so nothing works.

Chances are, if you get NO noise or vibration at all coming from the AC compressor, chances are the freon content is too low. Less often there is an electrical problem, such as with the switchgear itself or the AC clutch.

Other than checking all your fuses, there is not much you can do on your own. Most AC service requires expensive service equipment to perform properly, (aka visit your mechanic).

[Jrs3800]

Agreed... The 96 actually uses a pressure sensor that allows operation of the AC... If the pressure is to low the AC will not function..

I would take it in and have it checked over... If its never been charged it may be well past due.. Most Systems will leak down some over time, and over the years it can leak down enough to cause low refrigerant pressure in the system..

Have it checked out at a shop..

[brcidd]

Your '96 PA uses a V-5 compressor (first year on that model) and will stop cooling when refrigerant charge leaks down to about only 1/3 left in system. Most common failure mode is a leaky shaft seal and/or a compressor belly leak- both can be fixed- but most shops prefer to just replace the compressor. Compressor won't shut off until system pressure is less than 47 psi....which can be as low as a 5% refrigerant charge by weight. So running a compressor when it has hardly any refrigerant in it is really a bad thing to do--compressr needs oil and oil can only move adequate refrigerant charge- even though the V-5 does have a crankcase that store oil..

You can have it topped off for a less expensive fix-- but it has been my experiences that you will be lucky if it lasts the summer cooling season. Most leak back out within a couple months.

I actually reseal these compressors, new shaft seals and body o-rings and can get you another ten or more years out of your OEM pump....do 2 or 3 a week in the busy season...