1993 mgm ac not very cold/orifice tube

[Donal]

Ok. Here we go again. Last summer my ac wasn't blowing as cold as I figured it should. It is still using the R12 and I had some. Tried adding it, but the system wouldn't take it. So, I just let it go. This year, I have several cans of R12 and also several cans of oil, if needed. I would like for my ac to blow cold. From my reading , I figure the orifice tube is likely clogged up and needs changed. I'm confident that everything on this system is original. The car was owned by a little old lady from the time it was new, till she went into the nursing home. Some other yahoo owned it for about six months before I bought it, and he for sure didn't do anything to it. Anyway, I figure to replace the orifice tube and was wondering should I replace the accumulator too? Is there anything else to be done while I'm at it. What I'm looking at doing , is having someone remove the old refrigerant, I'll do what repairs/changes I'm going to do, then I figure on putting a vacuuming and recharging the system myself. Any advice and guidance is much appreciated.

Don.

[DerekTheGreat]

I'm no A/C expert but with my 1994 Ranger the problem was build up of crap between the condensor & radiator. Initially when I tried using the A/C it was warm or would sometimes get cool for an instant and go warm again. Once all the crap was cleared out the system was evacuated & recharged, all was well with the A/C up until my brother sold it last year.

[gadget73]

If the orifice tube is plugged, its likely from compressor shrapnel. The manifold gauges will tell you this.

If the system has been opened or empty, the accumulator must be changed.

Replace all of the O rings while you're in there. If it leaked out, find out why and fix that. Its usually O rings but not always.


I don't mean to sound like a total dick, but if you don't have a set of manifold gauges, I really wouldn't fool with this. Without knowing what the pressures are, you have no idea what the system is actually doing or where to start with fixing it. It may not even be the AC system, but the blend door inside the car. Those actuators fail too, and if yours won't shift to cold it won't cool the car off.

[Donal]

Thanks for the replies. The system has never, I'm confident, been opened. If, at some time in the distant past, it was opened, it would have been by a qualified tech. I do have a set of gauges, but have been afraid to try using them. I'm about to get brave

Don.

[lincolnlarry]

The line coming out of the compressor to the condenser should be hot. The short tube coming out of the evap. to the accum. should be cold. If that is good, then check into the ductwork. If that is not good, then it's the refrig. part itself and testing pressures will tell you more.

[gadget73]

another real basic test, if the compressor is running steady and not kicking in and out, the pressure is probably close to OK. These do have a high side cutout switch that will cycle if it is over-charged or if your fan isn't fanning, and if the blend door is jammed in the wrong place it will make the low side cycle out even with a proper charge. Again, the pressure gauges will confirm this.

[Donal]

Well, as I said, I do have a set of gauges. What I don't have is knowledge or expertise. I'm about ready to just shelf the project and leave it as is. I hooked the gauges up the other day. I found only one port that my gauge lines would fit, and that was the low side. The only other port I found, my gauge lines would not fit. So I checked the pressure on the low side.With the motor running and the ac on, it would go from 28 psi to 48 psi, then back down, etc. The ac clutch would click on about every 15 seconds for a few seconds. It was about 70 degrees outside. I didn't check the temp from the vents. There is no debris between the condenser and radiator. I'm gonna try adding a few pics.

[Donal]

Well, got some additional pics in there and they don't want to come out. Sorry about that.

Don.

[gadget73]

sounds about right for low side pressure. It will probably cut out the compressor under about 25 psi, and back on around 45. maybe yours is 28 out and 48 in. At 70F, it just may not be hot enough to keep the compressor running steady. Best chance for it would be to have the fan on full kick and the windows open to put max heat load into the system.

There are 2 different size high pressure R12 ports. There is the big GM size, and then the one that the rest of the world used. If your hoses have the fat GM connector, you'll need either a different high side hose, or an adapter to make them interface.


Pics came out, but random brake rotor shot and 1940s family photo in the group One of my cousins (I think she's actually a third cousin, would have to think harder on the particulars) married into a family with that same name. Any chance you have people around Bloomsburg, PA ? If so, its possible we're distantly unrelated.

[Donal]

Thanks. I'll check into another hose, or adapter. That's my father, his siblings and mother at the Craft cemetery in Ky.My line may have been in Pa at one time, but have been in Ky for the past couple hundred years.

Don.

[Donal]

Just did a quick check. Doubt if I'll be buying a hose. Might check Napa for a fitting.

Don.

[lincolnlarry]

I don't see how it can't be taking a charge. The only thing that would cause a system not to take a charge is higher then normal pressure on the low side. Yours are cycling low enough to trip the low pressure switch. I would look into why the r-12 isn't flowing into the system. If you checked the pressure through the same port you tried filling it through, I bet your fill equipment is to blame. Maybe it isn't opening the valve when connected?

[Donal]

Oh happy day! Thank you lincolnlarry for your suggestion about the equipment being at fault. Prolly wasn't the equipment, was prolly me having the hose on backwards or something. Anyway, used a different hose, making sure I had the correct ends connected, and tried adding some refrigerant. It took a whole can. The ambient temp was 75.4 and it brought the vent temp down to 35.4. I stopped with the one can, I didn't want to press my luck! Checked the low side pressure after the one can and it holds steady at about 26 psi, with the compressor running, then the compressor will kick out and the gauge will go up to about 46 psi and the compressor will kick on and the psi will drop back to about 26 psi, and run for a while , then kick out and repeat the cycle. Should I leave it alone at this point, or try adding more refrigerant? I am pretty much inclined to leave it alone at this point, as long as I'm getting cold air. Thank you everybody! Guess I'll be hanging on to those extra cans of R12.

[Mainemantom]

I would stop where you are at ! It is cold now. If you overcharge it or it builds up too much pressure, It will be dangerous /deadly if you are near it when a hose blows up. A/C systems are nothing to mess with unless a person is trained.
How much did the R12 cost you ? Hopefully it is not made in Mexico as they mix it with another gas. Very flammable.

[lincolnlarry]

I would stop there also. You will now be able to see if it leaks out or not. The other cans will be handy if you have a big leak and need to open the system up. Glad you got it sorted out!!!