Nitrogen vs Argon/CO2 mix to pressure test an AC system? - Page 2

nocarrier · 06-05-2011, 01:28 PM

I've never used freeze 12 before but 76 on the low side seems very high.

I don't know what the temperature is where you are but I usually shoot for around 35 or so at about 2000 rpm.

Tim Hancock · 06-05-2011, 01:53 PM

The low side seems high to me also???? I just charged my SC this morning and was around 200psi on the high side and 20 something on the low at 2000 rpm after (3) 12oz cans of 134.

mattdavis11 · 02:05 PM

Compressor is shot. You need new valve plates.

It could be that the expansion valve is stuck, back flush it if so.

A930Rocket · 06-05-2011, 01:57 PM

It's 85* here. I used 3 cans of the Freeze 12. Should I let a little out to lower the low/high side?

A930Rocket · 06-05-2011, 02:00 PM

Ouch...

Quote:

Originally Posted by mattdavis11

Compressor is shot. You need new valve plates.

mattdavis11 · 06-05-2011, 02:10 PM

Charge to 90% of what is recommend with r12 when using freeze 12. You didn't happen to charge as a liquid did you? That's why I said the valves are toast. Let the system equalize pressure and check it again.

High side is fine, the compressor is not sucking.

A930Rocket · 02:24 PM

Well, I'm over the 90% by a can I think and charged it as a liquid (like I've always done).

How do I backflush it?

What are the repercussions of driving it with bad valve plates? A new compressor is $295-325.

After checking it tomorrow, should I let a little out if it's still high?

Quote:

Originally Posted by mattdavis11

Charge to 90% of what is recommend with r12 when using freeze 12. You didn't happen to charge as a liquid did you? That's why I said the valves are toast. Let the system equalize pressure and check it again.

High side is fine, the compressor is not sucking.

Tim Hancock · 03:04 PM

I am not an expert on all AC systems, but I have always charged as a gas and use a hairdrier on the can to speed up the process. I do on occasion tip the can for short trickles of liquid, but too much liquid going into a "compressor" is not typically a good thing. Did the low side pressure stay at mid 70's or did it just spike up when filling? Maybe you got lucky and did not damage anything, but it does not sound good. I would definitely get rid of some of your charge and see if both your high and low side pressures come down to reasonable levels (like maybe 200 high/25 low). Too high of pressures on the high side, could be the result of a plugged expansion valve, but the high low side pressures are not an indication of a plugged expansion valve.

A930Rocket · 03:27 PM

The low side did spike up once or twice during the filling process. Afer two cans, the temp still felt low with my hand, so I decided to add the third can (you know if two is good, three is better

)

It's been a long time since I've recharged a system. I remember sitting the cans on a hot engine to help the process, so I might have done it backwards by filling as a liquid this time.

Quote:

Originally Posted by Tim Hancock

I am not an expert on all AC systems, but I have always charged as a gas and use a hairdrier on the can to speed up the process. I do on occasion tip the can for short trickles of liquid, but too much liquid going into a "compressor" is not typically a good thing. Did the low side pressure stay at mid 70's or did it just spike up when filling? Maybe you got lucky and did not damage anything, but it does not sound good. I would definitely get rid of some of your charge and see if both your high and low side pressures come down to reasonable levels (like maybe 200 high/25 low). Too high of pressures on the high side, could be the result of a plugged expansion valve, but the high low side pressures are not an indication of a plugged expansion valve.

Zeke · 06-05-2011, 03:48 PM

I *think* you can charge with the can upside down IF you keep your gauge low side barely open. Watch the low side pressure. I did freeze up a compressor once using the can upside down. To start the can off, use it right side up and as the low side goes way down and the can is getting light, that's when you might be able to turn it.

I wish I knew more about this as I have all the tools and some cans. I just can't find an adapter for the 12 oz cans locally. I didn't want to order it online in case it didn't work.

mattdavis11 · 04:01 PM

Quote:

Originally Posted by Tim Hancock

Too high of pressures on the high side, could be the result of a plugged expansion valve, but the high low side pressures are not an indication of a plugged expansion valve.

They can stick open just as well as closed.

What you have to be concerned with is liquid being compressed. Valves don't like that.

A930Rocket · 04:05 PM

Is the expansion valve servicable like some or is it a replacement part only? Looking online at them, it doesn't look servicable.

Get the side can adapter to pierce the can. It has two adapters so you can use different size cans. That's what I did for R12 fittings.

Quote:

Originally Posted by milt

I *think* you can charge with the can upside down IF you keep your gauge low side barely open. Watch the low side pressure. I did freeze up a compressor once using the can upside down. To start the can off, use it right side up and as the low side goes way down and the can is getting light, that's when you might be able to turn it.

I wish I knew more about this as I have all the tools and some cans. I just can't find an adapter for the 12 oz cans locally. I didn't want to order it online in case it didn't work.

A930Rocket · 04:27 PM

I guess my only options right now are to see if it equalizes, check the gauges and then let some out to see what happens.

At $13 a can locally, it can get expensive experimenting to get it right...

EDIT. I just remembered that with the AC running, I felt the AC lines in the engine bay and neither line was cold. The line from the compressor to evaporator should be cold, yes?

Tim Hancock · 06-05-2011, 04:30 PM

I still do not think it is his expansion valve Matt, but you and I both agree that he "might" have screwed the pooch by injecting a slug of "incompressible" fluid into a "compressor". "Hopefully" he just has too much refrigerant in the system.....

A930Rocket · 06-05-2011, 04:59 PM

I was looking at the gauges again and had a thought. The Freeze 12 is upposed to be the "same as R12". If you look at the gauge, should I be reading the red R12 numbers? If yes, then the low side doesn't change much. Maybe just a few PSI. But the high side is very different. If I read the red R12 numbers, the high side is 146 PSI.

Would that be correct reading and make a difference in what's wrong with it (compressor or expansion valve)?

nocarrier · 06-05-2011, 05:33 PM

I always use the large black PSI numbers on the gauge.

I find the best way to charge an a/c system is with a temp gauge in the center vent at the second slowest setting and watching the pressured on the gauge. Make sure all windows are closed and the system set to recirculate the air.

You can put the freon in as a liquid or a gas but when doing it with the bottle upside down (as a liquid) you have to be extra careful. Either way, when I first start to charge the system I wait for the compressor to engage. Once it has engaged I close the low side valve and watch to see if it immediately disengages or stays engaged. Depending on what is happening, I either let in some more freon or keep the valves closed and watch what the system is doing. I try and let in just enough freon so the compressor isn't cycling on and off immediately.

From that point on I am watching my gauges for my target pressure as well as the temp gauge of which I am shooting for about 40 degrees from the vent.

I slowly add freon and watch the temp gauge as well as my gauges to see if the temp is dropping with each addition of freon and my gauges are reading proper differences. Once I reach my targets, I know I have the exact amount of freon in the system.

Too much freon and the system can't cool properly. It's probably better t have a little less than too much.

This is how I've been doing it for years with awesome results.

Hope it helps....

mattdavis11 · 08:43 PM

That's spot on.

I wouldn't think it is either (exp valve), Tim, but allow it equalize and tell us what is going on. 105 PSI equalized is borderline over-charged for a 318, depending on the ambient temp. It's a 2lb system, that's 32oz. of refrigerant, and Tim is right, if you put in 3 cans, it has 4 ounces too much for R12, then add in the 90% factor b/c freeze 12 was used. Overcharged.

Your gauges are out of whack, adjust the brass screw to the right of the needle so it reads 0.

nocarrier · 06-06-2011, 04:34 AM

One more tip.....

When you connect your can of freon to your gauges don't forget to crack open the same hose at your gauges to purge any air out of the line.

Zeke · 06-06-2011, 06:58 AM

Quote:

Originally Posted by nocarrier

One more tip.....

When you connect your can of freon to your gauges don't forget to crack open the same hose at your gauges to purge any air out of the line.

That's where I don't get the R134a fittings. Quick connects that son't seem to really allow for that.

A930Rocket · 10:35 AM

Drove the car today and I was getting 40* temps, but it's about 5-8* cooler outside. I also noticed the low side line had condensation on it. With the overfill, I went ahead and let some out. How much? It's hard to tell. I do see bubbles in the site glass, where as yesterday, it was whiteish (maybe tiny foam looking bubbles). Checked the gauges and it looks like about 70 on the low side and 200 on the high side. I'll wait a day or two, drive and then install the gauges again.

At idle or low speed, the AC isn't as cool, but as I drive, it gets cooler. The aux fan is workng.

It does take it a while to blow cold air and cool the car down. It seems it has to overcome the heat in the car while parked.