Another A/C question

[foglght]

Bought cans of R12.

Started the car up, turned the A/C on after I hooked up the can to the low side.

Can started to get cold, a decent sign but didn't really notice that much going on. After a while, I took the can off to check pressure. The low side was still really low, but the high side was in the "danger" range on the gauge.

wtf is going on?

[Turf1600]

Clogged expansion valve?

[mutty]

Check if you have a dirty condensor. You may also have a restriction in the expansion valve.

[foglght]

Check if you have a dirty condensor. You may also have a restriction in the expansion valve.

These are things I really can't check unless I relieve all pressure from the system, right?

I have no way of getting it back to vaccuum state again.

[netcsk]

These are things I really can't check unless I relieve all pressure from the system, right?

I have no way of getting it back to vaccuum state again.

Correct.
You'll end up blowing the shaft seal in your compressor if you run it up too high.

[mutty]

These are things I really can't check unless I relieve all pressure from the system, right?

I have no way of getting it back to vaccuum state again.

Get a set of gauges and measure your pressures. 30psi[low side] and 160psi[highside] should be good. You do not need to get the system into vacuum to check for a dirty condensor. Get access to it and physically examine the condensor coil and make sure it is not clogged with leaves, small stones, etc. Also make sure that the fan is doing its job.

[Eric Giles]

mutty is right-if you are wanting to do your own A/C work, you absolutely must purchase a set of proper gauges. If your car has all of its original components and hasn't been worked on, then there are a few components that you really need to replace before you go any further. The expansion valve, receiver/dryer, and all the o-rings should be replaced. Pull a full vacuum on the system for at least an hour or more, then let it sit and see if the gauges are still showing the same negative vacuum pressure after another couple of hours with the pump off. If the pressure remains the same, you are ready to recharge the system. If you do lose some of that pressure, you have a leak and will need to find and fix it first.

[foglght]

Ok, the condenser looks decent. I've owned this car for 2 months now. The A/C blew ice cold when I bought it. Used the A/C once, and now its warm.

I did buy it from Colorado, and he lived at 7,300ft elevation. Not sure if that matters at all.

I'm not sure if I have a way to get the system to vaccuum. No places around me (Ann Arbor, MI) that will deal with it. Even the BMW dealer won't touch it.

I know the receiver dryer was replaced recently, and I assume that meant the system was recharged. I'd like to attempt to salvage the R12 I have left (3 cans) rather than converting to R134.

Thanks for the help guys.

[mutty]

Was the system charged with r134a or r12? Two months ago you would have had very cool outside air temperature so it would more than likely blow cool/cold. However as the temperature[ambient] increases, then the imperfections will show up. Find somebody who does hvac/r work and ask them to pull a vacuum on the system for you as long as you are certain that there is no leak on the system. The vacuum pump that is used by these guys have a larger capacity [5,6 or even 7cfm]. They can pull a better, deeper vauum much quicker than the 1.5cfm vacuum found in most mechanic shop.

[foglght]

It was charged with R12.

I'm stopping by Harbor Freight (ugh) to pick up a set of gauges tomorrow. A guy from work is going to let me borrow his vaccuum pump. It is pneumatic for my air compressor, so I shouldn't have any issues getting a good vaccuum.

From my experience (a long time ago) the expansion valves are fairly universal. I might even have one laying around at home. I'm so pissed I sold my gauge set after I hung up the tool belt at the dealer.

I haven't had to diagnose any of this crap in so long.

HAVE to get it fixed real soon. I drive my daughter in the car every day (6months old) and its going to be in the high 80's every day this week.

[mutty]

The pneumatic vacuum pump will not give you a good enough of a vacuum. Get the proper vacuum pump and do the good one time.

[quickervicar]

Have fun with that expansion valve. I just did mine on Saturday. Pull the glovebox & side trim to get at the evaporator cover to get at the valve. Tip: use a 25mm (or 1") wrench to hold the valve in place while you crack the lines. Those fittings can be a bugger to break free.

[foglght]

Well, today went to Harbor Freight to see about buying a gauge set. Of course, they don't sell a kit that contains R12 fittings, only R134.

So, went back home and attempted to add the rest of one of the cans. I can't read the high side accurately, but the low side said (with crappy gauge) about 38psi, which is just about right. Found some cold air coming from the vents, but not ice cold R12 air.

So, I really need to get an accurate set of gauges to read this and go from there.

Not sure what I'm going to do if the pressures are reading correctly. It's probably still the expansion valve.

Does anyone know how many ounces of refrigerant I'll need to refill the system? I have two cans left, sans oil.

[mutty]

38psi is too much for either r12 or r134a. You need to get that down to about 30/32psi.

[foglght]

I would let some out, but I don't trust the little tire pressure type gauge I have. Need to get some that I actually trust before I start lowering the pressure.