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A/C leak problem by crazyd
Started on: 10-16-2018 05:59 PM
Replies: 9 (301 views)
Last post by: crazyd on 10-19-2018 08:58 PM
crazyd
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Report this Post10-16-2018 05:59 PM Click Here to See the Profile for crazydClick Here to visit crazyd's HomePageSend a Private Message to crazydEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm trying to get my A/C working on the '88 GT in time for winter and it's time to throw out the lifeline. It's leaking, and I'm trying to find it and fix it.

I had a compressor in it that I replaced in 2002, which worked until about 2010. In 2013 I pulled the engine and interior for a major restoration, which went until 2017.

I replaced the O-rings at the rear manifold lines, the compressor, the accumulator, the LPCO, and the orifice tube. Still leaking under vacuum.

Took it to a shop to have it sniffed. Compressor is leaking they said, I figured probably the shaft seal.

I replaced the compressor, orifice tube & accumulator. NEW 4-seasons compressor, NOT reman.

At this point it held full 1" vacuum overnight.

Tried charging it. All seemed to be going well. At about 65F ambient, both sides got to about 50psi with 2 cans. All passive slow charge, engine & compressor NOT running. I screwed the caps on the ports and let it sit overnight as it was too cold to test.

Checked it today, 70F ambient, and the high side is holding at 50psi and the low side is now at 0. 0!

There's leak detector in the system. No signs of a leak at the compressor or manifold connection in back, nor up front at the accumulator or high side port.

The shop mechanic said he sniffed the condenser and evaporator and they did not appear to showing signs of a leak at that time.

I can't figure out why the low side would leak and the high side would hold, nor why any of this would happen when it holds full vacuum. Anyone?
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mad dad matt
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Report this Post10-17-2018 08:56 AM Click Here to See the Profile for mad dad mattSend a Private Message to mad dad mattEdit/Delete MessageReply w/QuoteDirect Link to This Post
1 inch vacuum won't tell you much.system should hold steady 15-28 inch for 15 min.Leak sniffers are good at finding leaks like kicking a tire tells you if it is low.Sounded like you did add dye to the system but apparently not showing a leak.When you say the low side was 0 psi dose your gauge indicate vacuum or is 0 the lowest it can read?Pulling a vacume on the low side indicates a blockage in the system . I must have misread but you charged both high and low with the engine off?? You charged the low side with the compressor running..Right?You then tested the low side the next day with the compressor running.If high side has 50psi and low is 0 (more likely a vacuum) with the compressor running you have a blocked line.You added 2 cans but what size are the cans?4oz or a keg?
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darbysan
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Report this Post10-17-2018 10:35 AM Click Here to See the Profile for darbysanSend a Private Message to darbysanEdit/Delete MessageReply w/QuoteDirect Link to This Post
I read the post as stating the pressures are engine off- just ambient pressures. High and low sides should balance out at same pressures when nothing is running. I've seen this before with my HF gauges- Low side not reading anything at all. First time I found a blockage in the Low Side port on the car. Second time it was the Low Side connection valve from the gauges. Remove the low side gauge connector, and push the Schroeder valve with a screwdriver, fingernail, etc. See if you get a spray of R134a. If you do, it may be your gauge. If it's the low side gauge connector, you can buy replacements on Amazon.

As a general rule, you want to pull 26" of vacuum for at least 15 minutes to test the system, and to help boil off any moisture in the system. Once you believe you have a good system, you then pull at least 30-45 minutes more vacuum time, again to boil off any moisture. Any moisture left inside the system can migrate to the evaporator and freeze, plugging your system. Also not good for your compressor.

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'87 GT , '00 3800 Series II SC, 4t65e, Vue Power Steering. (SOLD)

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Larryinkc
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Report this Post10-17-2018 11:05 AM Click Here to See the Profile for LarryinkcSend a Private Message to LarryinkcEdit/Delete MessageReply w/QuoteDirect Link to This Post
I am going to be working on my AC also. I found a product for AC O ring lube and fitting assembly called NYLOG blue. I haven't used yet but it looks good.

https://youtu.be/vAULfI8-Wwk
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crazyd
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Report this Post10-17-2018 11:40 AM Click Here to See the Profile for crazydClick Here to visit crazyd's HomePageSend a Private Message to crazydEdit/Delete MessageReply w/QuoteDirect Link to This Post
I misread the gauges, I pulled a full 29" of vacuum and it held overnight. I have been skeptical of the gauges and thought I might have had a leak in them, so I was disconnecting everything for the overnight leak tests. There's definitely 0psi at the low side, and 50psi at the high side. I charged 12oz cans in hot water without the engine running into both high and low sides.
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Raydar
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Report this Post10-18-2018 08:50 PM Click Here to See the Profile for RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
If it'll hold that kind of vacuum overnight, it would seem to be okay. If there's a leak, it's very slow.
The last time I heard, a Fiero system should hold three complete cans (36 oz.) of R134.

I usually turn on the A/C, jumper the pressure/cycling switch in the front compartment, and charge on the low side. ONLY. Usually via the accumulator port.
If it doesn't work, all you're out is the price of a couple cans of R134, and a bit of your time.

There is a formula for high side pressure vs ambient temperature, but 36 oz ought ot get you close to optimal.

Edit - I'm fighting this same issue. Except that mine loses vacuum in about 20 minutes.
It was recommended to me to just vacuum it down, charge it up, and see where the dye comes out.

[This message has been edited by Raydar (edited 10-18-2018).]

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fierobug
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Report this Post10-19-2018 06:19 AM Click Here to See the Profile for fierobugSend a Private Message to fierobugEdit/Delete MessageReply w/QuoteDirect Link to This Post
Had a very very slow leak that I could not find with the sniffer. Got a better AC light (had a cheap one) Mastercool-53517-UV-with the glasses and did it when really dark - great UV detector. Found it to be one of the pressure switches on the compressor. Looked real close you could see the dye seepage. Replaced the o-ring and good to go. The AC light changed the ballgame. Don't know if you have one already. Great your vacuum held. Like Raydar said give it a go and feed the refrigerant slow on low side - ONLY - with AC on and throttle it to get it through system clear air before loading. The blockage I had was the black death from previous owner - AC orifice tube coated. What a mess. Had to take the whole system apart to clean it completely. Good Luck and safe driving - I get nuts sometimes - great fun.

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[This message has been edited by fierobug (edited 10-19-2018).]

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mad dad matt
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Report this Post10-19-2018 08:12 AM Click Here to See the Profile for mad dad mattSend a Private Message to mad dad mattEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you held 29" vacuum overnight the system is sealed.Have you ran the ac compressor at all?Attach your gauges,start the engine,ac max fans high.If you have 0 on low side pressure switch will not allow the compressor to engage.Start adding a can to the low side.in 3 second bursts.The pressure should clime on the low side and compressor clutch will engage and pressure will drop.The pressure will rise and drop to 0 several times then it should rest at 1,then 2,and start to clime before you finish the can.The high side pressure should be closer to 150 .and low side 35 at 65-70 deg.If the high side climbs to 170ish and low drops below 20 you have a blockage.Without the compressor running the max pressure you can hit is max pressure in a full can. Until the system has a adequate charge the compressor will fill the high side.After it is full the expansion valve will open flowing back to the low side.
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crazyd
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Report this Post10-19-2018 03:07 PM Click Here to See the Profile for crazydClick Here to visit crazyd's HomePageSend a Private Message to crazydEdit/Delete MessageReply w/QuoteDirect Link to This Post
When in doubt, check your gauges! i rented a different set from a FLAPS and see 45psi on the low side. i still can't get the compressor to engage yet even with the LPCO bypass trick, but since i had to do the switches as well i think i just need to find a good ground for the new wire. i'm using the bit that the firewall heat shnield screws to.

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crazyd
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Report this Post10-19-2018 08:58 PM Click Here to See the Profile for crazydClick Here to visit crazyd's HomePageSend a Private Message to crazydEdit/Delete MessageReply w/QuoteDirect Link to This Post

crazyd

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Member since Feb 2002
Compressor engaged and pressures holding, apparently there was never a leak in the first place. We'll call this one good, but another problem still exists and I'll start a new thread for that.
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