Holds Vacuum on Low Side Only - Team Camaro Tech
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post #1 of 13 (permalink) Old Jul 20th, 11, 04:24 PM Thread Starter
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Holds Vacuum on Low Side Only

Okay, I had to take my new compressor off in order to take out the PAG oil for r134a & add mineral oil for the R12 refrigerant.

I put everything back together.

Now the system only holds a vacuum on the low side, right @ 28 Hg.

When I turn the vacuum pump off with the low side (blue hose) open & the high side (red) closed, the system will hold a vacuum.

If I open the high side gauge, the low gauge loses its vacuum reading & goes back down to zero pretty quickly.

All the components on the high side are brand new (Pro6ten compressor, new dryer/receiver, new condenser, new hoses).

Also, when I have the vacuum pump on with the high side gauge open, the pump wonít ever stop putting out either steam or smoke (I canít tell which it is). When I close the high side gauge the steam/smoke stops right away.

I tried to be VERY CAREFUL about how much mineral oil I put in the new compressor. My problems started, right after I changed the oil.

I have sent off (via ebay) for a little leak detection dye kit.

If anyone has any suggested concerning these symptoms Iíve described, I would really appreciate your input.
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post #2 of 13 (permalink) Old Jul 20th, 11, 04:53 PM
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Dan Ensign
 
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Re: Holds Vacuum on Low Side Only

CHeck the o-ring on the high side fitting at the compressor, you may have damaged it during reassembly, these o-rings should always be replaced and lightly lubed with compressor oil.

Dan E.
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post #3 of 13 (permalink) Old Jul 20th, 11, 07:13 PM
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Re: Holds Vacuum on Low Side Only

I dont know to much about POA valve systems buy on a typical expansion valve / orifice tube with the system off both low and high side equalize meaning if a normal system runs 300psi on high side and 40psi on low side when it turns off it will be about 100psi on both the high and low side.

So if you say you open the high side and it goes to zero then you have a leak on the high side. Like said above check all your o-rings and connections on the high side.

Mike
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post #4 of 13 (permalink) Old Jul 20th, 11, 11:02 PM
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Re: Holds Vacuum on Low Side Only

Quote:
Originally Posted by 327!275hp!Convt! View Post
Okay, I had to take my new compressor off in order to take out the PAG oil for r134a & add mineral oil for the R12 refrigerant.

I put everything back together.

Now the system only holds a vacuum on the low side, right @ 28 Hg.

When I turn the vacuum pump off with the low side (blue hose) open & the high side (red) closed, the system will hold a vacuum.

If I open the high side gauge, the low gauge loses its vacuum reading & goes back down to zero pretty quickly.

All the components on the high side are brand new (Pro6ten compressor, new dryer/receiver, new condenser, new hoses).

Also, when I have the vacuum pump on with the high side gauge open, the pump wonít ever stop putting out either steam or smoke (I canít tell which it is). When I close the high side gauge the steam/smoke stops right away.

I tried to be VERY CAREFUL about how much mineral oil I put in the new compressor. My problems started, right after I changed the oil.

I have sent off (via ebay) for a little leak detection dye kit.

If anyone has any suggested concerning these symptoms Iíve described, I would really appreciate your input.
Whenever you open a system up and then close it you need to do a leak check prior to pulling a vacuum. Do you have access to dry nitrogen? If not then get a couple cans of 134 and pressurize the system and use soapbubbles around the fittings to check for leaks.

I'll bet you have a big enough leak that it is noticeable without soap bubbles. As Dan said, get some new o-rings, lube em up and reinstall carefully.
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post #5 of 13 (permalink) Old Jul 21st, 11, 06:29 AM
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Chuck
 
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Re: Holds Vacuum on Low Side Only

Sounds more like something wrong with your gauge set. The system can't just leak refrigerant from one side so, it can't just hold vacuum on one side. It will attempt to equalize pressure and vacuum when not operating.
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post #6 of 13 (permalink) Old Jul 21st, 11, 08:15 AM
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Dave
 
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Re: Holds Vacuum on Low Side Only

I would look at the gauges more closely. In these systems, they should quickly equalize pressure when turned off. Evacuating the system from either the high or low side evacuates the entire system so the readings should be exactly the same from either side prior to the system being charged. A leak anywhere in the system would quickly drop the vacuum readings to zero on either port once the vacuum pump is removed from the system.

There is no reason to have hoses connected to both ports for evacuation. I usually connect to the low side, but it works from either. As a test, evacuate from one port with one gauge connected, close the gauge and watch for bleed down. Assuming all is well, you could repeat using the same gauge on the other port. I bet you find the system is fine and the leak is in your gauge set.

Dave

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post #7 of 13 (permalink) Old Jul 21st, 11, 09:27 AM Thread Starter
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Re: Holds Vacuum on Low Side Only

My prayers were answered (Iím such a big dummy).

I changed out the two big O-rings at the back of the new Pro6tenÖ did not help.

I decided to go around to EVERY fitting I could find & double check that they are nice & tight.

To my surprise (BOTH) the fitting on the dryer were only hand tight.

This still didnít fix the problem though.

So I when around to each & every hose clamp to double & triple check those.

I tighten each one to the point that I was afraid I might strip the hose clamp.

When I came to hose camp on the bottom of the condenser (it was nice & tight) I cranked down on it anyway. As soon as I did, the vacuum pump started sounding different. I looked at it, & it FINALLY stop pumping out steam or smoke. I knew this was an excellent sign. I waited a minute. Next, I turned off the vacuum pump & the gauge reading held rock solid.

Maybe Iíll have a working ac system this summer yet.
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post #8 of 13 (permalink) Old Jul 21st, 11, 11:05 AM
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Re: Holds Vacuum on Low Side Only

Quote:
Originally Posted by 327!275hp!Convt! View Post
My prayers were answered (I’m such a big dummy).

I changed out the two big O-rings at the back of the new Pro6ten… did not help.

I decided to go around to EVERY fitting I could find & double check that they are nice & tight.

To my surprise (BOTH) the fitting on the dryer were only hand tight.

This still didn’t fix the problem though.

So I when around to each & every hose clamp to double & triple check those.

I tighten each one to the point that I was afraid I might strip the hose clamp.

When I came to hose camp on the bottom of the condenser (it was nice & tight) I cranked down on it anyway. As soon as I did, the vacuum pump started sounding different. I looked at it, & it FINALLY stop pumping out steam or smoke. I knew this was an excellent sign. I waited a minute. Next, I turned off the vacuum pump & the gauge reading held rock solid.

Maybe I’ll have a working ac system this summer yet.
I would not trust hose clamps. I would have the fittings crimped with the correct fittings.

You will have up to 300psi on the hoses on the high side.

Mike
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post #9 of 13 (permalink) Old Jul 21st, 11, 12:07 PM
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Re: Holds Vacuum on Low Side Only

I figured you had a leak. Still do a pressure check prior to pulling final vacuum. And there is absolutely nothing wrong with pulling a vac from both low and high side at the same time.
Pull a good vac. Let it set for an hour and come back and check if it held.
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post #10 of 13 (permalink) Old Jul 21st, 11, 02:16 PM
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Re: Holds Vacuum on Low Side Only

67 and 68 A/C fittings had hose barbs and radiator clamps on most of the fittings, wasn't until 69 that all of the hose ends were swagged to the pipes. The radiator clamps are for A/C systems with a little dog leg bracket coming off them that sits against the aluminum pipe section that the hose fits over to keep them from getting installed to far down the hose.

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post #11 of 13 (permalink) Old Jul 22nd, 11, 05:52 AM
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Re: Holds Vacuum on Low Side Only

Hose clamps/barbs or crimped connections aside, if he's gonna use 135a, he needs barrier hose to keep the 134a inside.

And.... if he's gonna swap hoses, now would be the time for crimped connections.
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post #12 of 13 (permalink) Old Jul 22nd, 11, 12:13 PM
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Re: Holds Vacuum on Low Side Only

did you read the first sentence of this port?
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post #13 of 13 (permalink) Old Jul 22nd, 11, 12:23 PM
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Re: Holds Vacuum on Low Side Only

I agree the crimped connections are better, but the shape of the manifold that mounts to the back of the compressor makes it just about impossible to get a modern crimp tool on it, so you likely need to go with a hose clamp there anyway. If you are using one clamp, you might as well use all of them.

Also, both crimps and hose clamps both come down to how well they are installed. A properly installed hose clamp works just as well as a crimp. It has been proven that hose clamps are just as effective for modern refrigerants as crimped hoses.

Dave

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