A/C High-side vs. Low-Side
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From: Shreveport, LA
A/C High-side vs. Low-Side M'kay...
Compressor is quiet and cycles/runs fine (based on general observation)
System was empty. System ingested 1 and 1/8 cans of coolant charge, and quit sucking any more after that. Air never got cold.
DIAGNOSE:
High Side:
Press in schrader valve, TON of pressurized coolant sprays.
Low Side:
Depressing shrader valve produces nothing.
Discuss.
Compressor is quiet and cycles/runs fine (based on general observation)
System was empty. System ingested 1 and 1/8 cans of coolant charge, and quit sucking any more after that. Air never got cold.
DIAGNOSE:
High Side:
Press in schrader valve, TON of pressurized coolant sprays.
Low Side:
Depressing shrader valve produces nothing.
Discuss.
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From: Jacksonville, FL
Are you using gauges? If it was empty you need to pull a vacuum before trying to recharge. With the car off the system should equalize according to the ambient outside temperature - for example, about 82 degrees should be close to 100 psi, then drop down when the compressor starts. Gauges will tell you if there is a restriction - low suction/high head pressure.
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Upon insertion of the first can, the gauge initially indicated about 100psi, and dropped to roughly 95psi. The low-side fitting "froze up" pretty good, that is to say, it developed thin slush/ice on the metal fitting. Shaking the can as instructed resulted in a slight rise in pressure.
Then, after the first can emptied, hooked up the second can. The frozen quality of the metal fitting on the low-side diminished greatly. Gauge then stayed somewhere between 105psi and 110psi, never really fluctuating.
Again, the high side seems to contain all the coolant pressure. The low side, not so much... i.e. no schrader valve reaction, and no cold air out the vents.
Then, after the first can emptied, hooked up the second can. The frozen quality of the metal fitting on the low-side diminished greatly. Gauge then stayed somewhere between 105psi and 110psi, never really fluctuating.
Again, the high side seems to contain all the coolant pressure. The low side, not so much... i.e. no schrader valve reaction, and no cold air out the vents.
Did you pull a vacuum?
Possibly a clogged orifice tube. . . . .
My way of diagnose(yes, this is not the EPA way): Let the 134a out, pull vacuum for 45 minutes, fill it up with 1.5 cans(I think that is what ours takes, but I have not done this for a bit). Check low and high pressures. . . . Go from there.
Possibly a clogged orifice tube. . . . .
My way of diagnose(yes, this is not the EPA way): Let the 134a out, pull vacuum for 45 minutes, fill it up with 1.5 cans(I think that is what ours takes, but I have not done this for a bit). Check low and high pressures. . . . Go from there.
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From: Turnin' Wrenches Infractions: 005
Let me clarify on this a tad for the record. This is not on a Z. This is on a 90 Nissan Hardbody P/U. An old R12 system. The compressor appears to be new as is the engine and everything else under the hood as the truck was just purchased recently. NO we didnt pull a vacuum, the system was only open long enough to replace a pinched o ring but has been under positive pressure so there was no indication that moisture or anything else could have gotten in. Now I know this isnt the best/right way to do it, however thats not what 1FSTz is asking.
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From: Shreveport, LA
Yes, I probably should have been more clear, but I valued generalized answers from a basic automotive A/C system perspective. This '90 Nissan Hardbody pickup obviously originally came with an R12 system, but understand that I bought it with a new drop-in motor/AC system, etc... all new under the hood.
SO, with that being said, it has obviously been upgraded, as it has R134a fittings on the system.
Conclusively, no a vacuum hasn't been pulled, but yet nor is there a leak even remotely apparent. Hell, even the evaporator actively drips condensation under the truck while the system runs... but no cold air comes out the vents.
Furthermore, and to repeat the previous statements, the low side's schrader valve has no coolant pressure; yet the high side has tons.
SO, with that being said, it has obviously been upgraded, as it has R134a fittings on the system.
Conclusively, no a vacuum hasn't been pulled, but yet nor is there a leak even remotely apparent. Hell, even the evaporator actively drips condensation under the truck while the system runs... but no cold air comes out the vents.
Furthermore, and to repeat the previous statements, the low side's schrader valve has no coolant pressure; yet the high side has tons.
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Again, 1990 Nissan D21 pickup with the factory; albeit brand new, crate KR20 engine (the 240SX motor).
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From: Tulsa, OK
OK....this is something you need to look at. If it's an orifice tube, it could be plugged. If it's an expansion valve, it could have a broken capillary tube or broken bulb at the end of the tube (this is what controls the valve) or it could be plugged, and if it's capillary expansion, the capillary tube could be kinked/broken or plugged.
Another possibility is moisture in the system causing an ice ball at the outlet of the expansion device.
The other possibility is a clogged evaporator, but that's pretty rare.
Another possibility is moisture in the system causing an ice ball at the outlet of the expansion device.
The other possibility is a clogged evaporator, but that's pretty rare.
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From: Shreveport, LA
fleetmgr,
Would you happen to know what kind of expansion device the oldschool R12 systems typically used?
I mean if it comes down to it, I suppose we can disassemble all the lines and flush them.
It just seems as though the solution should be somewhat simple. By saying that, I mean.... We have pressure like a sumbitch coming outta the high side when we press the schrader valve, yet none on the low side.
The main device in between seems to be the compressor, yet the compressor is apparently functioning normally. So, it's like WTF is happening in that short physical distance between the low side --> compressor --> high side ???
MUST be a blockage of sorts!?
Would you happen to know what kind of expansion device the oldschool R12 systems typically used?
I mean if it comes down to it, I suppose we can disassemble all the lines and flush them.
It just seems as though the solution should be somewhat simple. By saying that, I mean.... We have pressure like a sumbitch coming outta the high side when we press the schrader valve, yet none on the low side.
The main device in between seems to be the compressor, yet the compressor is apparently functioning normally. So, it's like WTF is happening in that short physical distance between the low side --> compressor --> high side ???
MUST be a blockage of sorts!?
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From: Tulsa, OK
I mean if it comes down to it, I suppose we can disassemble all the lines and flush them.
It just seems as though the solution should be somewhat simple. By saying that, I mean.... We have pressure like a sumbitch coming outta the high side when we press the schrader valve, yet none on the low side.
It just seems as though the solution should be somewhat simple. By saying that, I mean.... We have pressure like a sumbitch coming outta the high side when we press the schrader valve, yet none on the low side.
If it's an expansion valve system, and the capillary tube/thermo bulb that controls the valve gets kinked/broken/plugged then it'll never pass any refrigerant. Same with a capillary expansion system or a orifice tube system. Moisture in the system that freezes = plug.
Last edited by fleetmgr; May 15, 2010 at 10:49 PM.
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fleetmgr:
Most interesting that you brought up the jumped compressor scenario. Remember participating in this short-lived thread?
https://ls1tech.com/forums/general-m...-ac-issue.html
So, yes actually... we ended up initially jumping the compressor. It took in that 1 and 1/8th can and then quit sucking it up.
Now with that 1 and 1/8th can in the system, the compressor now kicks on with no problem, jumper removed.
Yet... no cold air, no low side pressure...but apparently enough in some way, shape, or form... to activate the compressor.
Most interesting that you brought up the jumped compressor scenario. Remember participating in this short-lived thread?
https://ls1tech.com/forums/general-m...-ac-issue.html
So, yes actually... we ended up initially jumping the compressor. It took in that 1 and 1/8th can and then quit sucking it up.
Now with that 1 and 1/8th can in the system, the compressor now kicks on with no problem, jumper removed.
Yet... no cold air, no low side pressure...but apparently enough in some way, shape, or form... to activate the compressor.
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From: Shreveport, LA
UPDATE:
Figured I'd update this thread with our findings.
This primarily goes out to all the folks with an upgraded R12 system.
If you experience what we did, the fact that the compressor correctly self-activated was the hint. Cranked the truck the next day and turned on the AC to see what would happen. Low and behold, it had moderately cool air.
We put another can in it, and as this 2nd can emptied, my buddy switched from "Full Face" to "Face and Feet." It made the compressor cycle differently, and like a little miracle, the damned gauge dropped right there in front of us.
Fully charged, ice cold air. WIN.
Conclusion:
When dealing with an older upgraded system, be PATIENT.
Figured I'd update this thread with our findings.
This primarily goes out to all the folks with an upgraded R12 system.
If you experience what we did, the fact that the compressor correctly self-activated was the hint. Cranked the truck the next day and turned on the AC to see what would happen. Low and behold, it had moderately cool air.
We put another can in it, and as this 2nd can emptied, my buddy switched from "Full Face" to "Face and Feet." It made the compressor cycle differently, and like a little miracle, the damned gauge dropped right there in front of us.
Fully charged, ice cold air. WIN.
Conclusion:
When dealing with an older upgraded system, be PATIENT.
Congrats on the win but you really need to pull a vacuum if you haven't already. Moisture in the system will break down the compressor oil and in a short time you will be dealing with some "black death." Its absolutely critical to the AC system.
