My 1995 Bonneville SE has 136,000 miles, runs quite well. However, the A/C works only marginally. It works best at Bi-level, the two higher settings don't seem to work.

If you watch the compressor & clutch while it's running, you can see the compressor clutch kicking in/out, in/out continuously, about every six seconds. I don't think it's supposed to do that. I checked the pressure on it, the pressure rises and falls with the clutch going on/off, on/off. When it's at max the pressure is adequate, then drops. Rises and falls every few seconds.

Any ideas what is happening?

Low freon maybe.

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1994 Bonneville SE - Series one. L27
1998 Bonneville SE - Series Two. L36
2001 Bonneville SSEI - Series Two. L67

If you don't understand air conditioning, you should not be messing it.

It's a douchebag response, i know, but it really is the truth. The system is likely low on refrigerant, but it also should be a sealed system, so if there is nothing in it, it must have leaked out somewhere. Now, pressures. The pressure should be checked with it running. The compressor should kick out when it drops below 20-25 psi on the low side, or if the high side overpressures (400 psi comes to mind). When you check only the low side pressure you only get half the picture. If you say the low side pressure looks good with the system off, then low refrigerant is most likely to blame. A properly charged system is usually 100-120 psi at rest.

If I was faced with your scenario, i would charge the system with an oil/seal conditioner/uv dye charge, and 1 can of r-134a. By the end of this, the system should be behaving much better. I would expect a second can to go in, and everything be happy. If it goes out again, you can find the leak with a black light.

the proper method is to pull a full vacuum on the system, hold it for 30 minutes, then pump the n the appropriate amount of oil and refrigerant by weight (uv dye recommended still). Check locally, but plan $200 for this after labor and refrigerant, not even counting the talley if something has a problem Special equipment is required.

And this post comes with a warning. This particular system on your car can cause serious injuries if you are in the wrong place and a failure occurs (seriously, blindness and hearing damage are REAL dangers here).

no seriously, i had a valve fail on mine and didn't realize it until i took off the retrofit fitting. The refrigerant loss was deafening and left oil spray all over my sunglasses, and thankfully i was to the side when this 15 foot plume erupted. I thought even i knew what i was doing, and still learned a hard lesson that day. It could have very easily gone much worse.

if you dont know, leave it to someone who does.

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~Randall~


1993 Buick Park Avenue - 197k - Some odds and ends done - Simply won't die
1994 Buick Regal - 78k - Bone stock - Always ready for a good kicking
1990 Oldsmobile 88 - Gone to a better place

Low coolant it is. The difficulty is to know which pressure reading is significant, because it keeps changing. As you add coolant when the A/C is on (which is how you're supposed to do it), the clutch is going in/out. And the pressure goes down when the compressor kicks in, not up. I added about 1 1/2 cans of R134a to the system. The pressure reading is at 100 psi when the engine is off, and now the A/C works just fine. I think the 100-120 psi at rest is what you need to aim for, don't rely on any numbers you get while it is running.

I've only had this car since last year, probably the previous owner didn't use the A/C, or didn't try to fix it when it failed. The pressure didn't change since I partially filled it last year. So it may have leaked out very slowly. And there is no retrofit, it's factory A/C. If it leaks out quickly (as opposed to over a period of years) I'll have to get it serviced.

specifications-and-general-information/topic1737.html

These are the factory specs. The nature of refrigerant is that it is a liquid that boils at a very low temperature, however pressure increases the boiling point. So the system will always show the same pressure at rest whether it is almost empty, or dangerously overfilled. Pressures must be measured when it is running for accurate results. The pressure should drop on the low side (where you add) and raise on the high side when the compressor is engaged. When the low side gets too low or the high side gets too high, the compressor disengages. If pressures are not consistent with the chart it indicates an issue.

_________________
~Randall~


1993 Buick Park Avenue - 197k - Some odds and ends done - Simply won't die
1994 Buick Regal - 78k - Bone stock - Always ready for a good kicking
1990 Oldsmobile 88 - Gone to a better place

You have a leak. Take it in for a vacuum and recharge with dye. I just did a vacuum and recharge a LeSaber and a Park Ave and charged $!115 after tax. The H bodies take 2lbs of R134. If it is just a service valve, add another $15 per valve. Lines can run a couple of hundred dollars, but once lines start getting replaced, the dryer and orifice tube should get replaced as well. New compressor, orifice tube, dryer, flush, and labor should run around $12-1500.

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1998 Bonneville SE - Dark Gray Green Metallic
2009 Mercury Mariner
2005 V Star 650 Classic