Trying To Fix My A/c

LarsD

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Hey guys, kind of frustrated here. Could years ago I had a slow leak in my a/c system on the LX. This was right about the time I was planning on swapping the engine. I discovered it was the high pressure hose that was leaking so I swapped it out while I had everything apart.

Fast forward to now. I borrowed a vac pump and gauge set (older HF stuff), the couplers were shot so I replaced them. I also put new 134a adapters on the car was well (the car has 143a in it when I got it and worked fine). I was able to evac the system for over 30 minutes and then let it sit for an hour at it stayed near 30psi of vacuum.

I just came in from trying to put refrigerant in the system and I can't get it to take any of it. The low side gauge is reading around 90 psi, which doesn't seem right at all. The clutch on the compressor is engaging, but I can't get it to draw any in, I burned like two hours trying to troubleshoot the gauges to make sure they are actually opening and they are. What am I missing here?

ETA: I think the gauges may be messed up. Because while troubleshooting the setup, despite the gauges telling me the low side was at 90 psi, when I popped an open coupler of the low side port to verify that briefly, it pushed very little pressure out. So I am wondering if the pressure readings I am getting are confined to the hoses and it actually isn't making it into the system. No refrigerant is moving past the site glass on the gauge manifold.
 
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Boosted92LX

It's only an inch or two. What's the big deal?
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When you run the screw down to pierce the can are you backing it back out so the gas can flow? That one got me a while back. Derr.
 

LarsD

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When you run the screw down to pierce the can are you backing it back out so the gas can flow? That one got me a while back. Derr.
Yeah no I am doing that. I used it to purge the lines on the gauges to make sure the manifold valves were actually working. I am thinking the valve cores in the hoses are getting forced closed by the pressure of the refrigerant in the can and I am only reading the pressure in the lines. Nothing is flowing in the sight glass.
 

LarsD

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It is an older Harbor Freight set of gauges. I ordered a new set of Robinair gauges tonight, hopefully that will solve the issue.
 

84Ttop

They make new pistons every day, so why worry?
Mod Dude
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It's possible that the inner portion of the gauges aren't depressing the schrader on the system in the car. I can't tell you how many times I've seen this over the years. Good gauges are a start, if you have an extra adapter laying around spin that into the gauges (not attached to the car) and try to push refrigerant through them. There should be a very small brass bridge in the swivel end of the gauge hoses, they sometimes bend and or break off
 
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Mustang5L5

This is a big reason why I pulled it out
Mod Dude
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If you are reading 90PSI on the low side with compressor engaged, you are overcharged.

Something is def up with those gauges.
 

rbohm

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are you sure that you are trying to put the refrigerant in the low side and not the high side? it has happened before that some one would mix up the ports.
 

LarsD

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It's possible that the inner portion of the gauges aren't depressing the schrader on the system in the car. I can't tell you how many times I've seen this over the years. Good gauges are a start, if you have an extra adapter laying around spin that into the gauges (not attached to the car) and try to push refrigerant through them. There should be a very small brass bridge in the swivel end of the gauge hoses, they sometimes bend and or break off
Yeah I am suspecting the Schraders might be shot. Hoses aren't in real good shape on these gauges either.

If you are reading 90PSI on the low side with compressor engaged, you are overcharged.

Something is def up with those gauges.
Yeah it is shooting up to 90 psi almost immediately, but when I open the system (popped on a one of those quick fill setups that I had laying around from a couple years ago) the system was still under vacuum.

are you sure that you are trying to put the refrigerant in the low side and not the high side? it has happened before that some one would mix up the ports.
Yeah definitely not opening the high side.
 

LarsD

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Got my new gauges in a few weeks ago. Finally got to the car today. It started taking refrigerant with the new gauges so I guess my friend's set is hosed. Took two cans (28-30 oz approx). Could only get it down to about 60 degrees in the shop. Felt good though. I didn't want to crack a third can open just for a couple of ounces. So I took it for a test drive. On max A/C rolling down the road it dropped to 45 degrees from the center vent, felt great. Finally after 5 years the car has work A/C again.
 

jrichker

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With R134a, 24-28 Oz is about right on the mark.

R134a refrigerant charge is smaller than R12, I think it is 80% of the amount of R12.
 

LarsD

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With R134a, 24-28 Oz is about right on the mark.

R134a refrigerant charge is smaller than R12, I think it is 80% of the amount of R12.
Yeah I had heard/read that somewhere before that you didn't need as much 134a as you do with R12. Good thing cause I didn't want to crack open a third can for just a couple of ounces. Not looking forward to my truck, it takes like a couple of gallons of refrigerant.
 

LarsD

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Well it was fixed. Went to get it out of the garage, A/C was blowing hot, looked at the floor and there is oil all over it. It is puking (what appears) to the be oil out of the drain on the firewall. I guess the evap core died on me.
 

jrichker

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Maybe a stray screw stabbed the evaporator. That would account for the slow loss of refrigerant and now the oil leak. The evaporator replacement is the same basic process as replacing the heater core.
 

LarsD

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Maybe a stray screw stabbed the evaporator. That would account for the slow loss of refrigerant and now the oil leak. The evaporator replacement is the same basic process as replacing the heater core.
Well the car held a vacuum for weeks while waiting for me to get proper gauges, etc. Looking at the floor of my garage it looks like it asploded. I will probably just shotgun the heater core and evap at the same time. I was thinking about this kit. Though I will likely wait till a little later if I decide to go that route.

Mustang Air Conditioner (A/C) Conversion Kit W/O Smog Pump (87-93) 5.0L
 

liljoe07

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Well the car held a vacuum for weeks while waiting for me to get proper gauges, etc. Looking at the floor of my garage it looks like it asploded. I will probably just shotgun the heater core and evap at the same time. I was thinking about this kit. Though I will likely wait till a little later if I decide to go that route.

Mustang Air Conditioner (A/C) Conversion Kit W/O Smog Pump (87-93) 5.0L
Reasons like that is one of the reasons why we pressure test the system in the AC trade.