AC low side high pressure
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AC low side high pressure
Finally got to the 89 bronco's ac. Whole system was replaced 3 years ago and converted to 134a about 3 summers ago. Wasn't working this year so I put gauges on and got low pressures, as soon as I put a can of 134a on, low side pressures shot up well over 100, compressor would pump for a second or two, the low side would hike up, then compressor would shut off and low side would come down to about 70-100. High side when pump engaged would be 150-200 then drop below 100 when disengaged. I checked the orifice tube, there was a bit of sediment, not black, more greyish. Flushed air and solvent through the low line from condenser to orifice tube, then backflushed the evaporator and blew it out well. No blockages or dirt. Replaced the accumulator and orifice tube, pulled a vacuum for several hours, then tried to refill, same thing, it wouldn't even take a 12oz can before pressures on low side would shoot up. Think it is the compressor or the suction lines blocked?
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No. I took the compressor off and you can spin it by hand with almost no resistance so it's obviously shot. Got another at a local store. Hooked everything back up, pulled a vacuum. Put a can of 134a on and it shot the low pressure up to about 75psi but high pressure is still reading 0. Jumped the pressure switch and doesn't do much so there must be restriction in the evaporator? Weird because I blew that out with air and it seemed fine. Or could it be the condenser?
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From: St Louis
The reaction of the low side gauge is normal, you're reading the pressure from the can.
If your high side gauge is reading zero, either the gauge is defective, that hose's valve is turned off, or the connector/coupler/valve is defective. Both sides should read the same when the supply is first connected and before the compressor activates.
When you charged into a vacuum, that first can or so of refrigerant should pretty much jump into the system without even turning it on. If you pre-warm the can, it goes faster. I used to put the cans in a bucket of hot water or leave them in the sunlight for a while to speed it up.
If your high side gauge is reading zero, either the gauge is defective, that hose's valve is turned off, or the connector/coupler/valve is defective. Both sides should read the same when the supply is first connected and before the compressor activates.
When you charged into a vacuum, that first can or so of refrigerant should pretty much jump into the system without even turning it on. If you pre-warm the can, it goes faster. I used to put the cans in a bucket of hot water or leave them in the sunlight for a while to speed it up.
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The reaction of the low side gauge is normal, you're reading the pressure from the can.
If your high side gauge is reading zero, either the gauge is defective, that hose's valve is turned off, or the connector/coupler/valve is defective. Both sides should read the same when the supply is first connected and before the compressor activates.
When you charged into a vacuum, that first can or so of refrigerant should pretty much jump into the system without even turning it on. If you pre-warm the can, it goes faster. I used to put the cans in a bucket of hot water or leave them in the sunlight for a while to speed it up.
If your high side gauge is reading zero, either the gauge is defective, that hose's valve is turned off, or the connector/coupler/valve is defective. Both sides should read the same when the supply is first connected and before the compressor activates.
When you charged into a vacuum, that first can or so of refrigerant should pretty much jump into the system without even turning it on. If you pre-warm the can, it goes faster. I used to put the cans in a bucket of hot water or leave them in the sunlight for a while to speed it up.
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From: St Louis
You still haven't explained why both gauges do not read the same static pressure before the compressor is activated. That's either a problem with your manifold set, how it is being used, or a connection isn't open.
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I understand that. That's what's confusing me as well. But doesn't the fact that very little can go into the system point to some sort of restriction? I have a can with maybe 2 oz in it hooked up and it wont drain it. Both gauge lines are hooked up and opened at the Schrader valves, manifold is turned off at high side, I open low only to put Freon in. When I manually engaged the compressor (jumped the switch), the high side pressure would raise just a little, but go back to 0 when off.
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From: St Louis
Do this: Engine OFF.
Open BOTH valves on the manifold and allow the can's contents to be directly exposed to both ports. Allow equilibrium to be reached. Both gauges should read the same, roughly static pressure based on your local ambient temp. If they don't, you have a problem with the manifold gauge set.
Could be a number of things. Like I said previously, a fully vacuumed system in which vacuum integrity was maintained should allow a full can to go into the system without ever starting the engine. Di you verify that the system HOLDS vacuum after it was vacuumed?
BTW, did you flush or blow air through the condenser to verify it's not restricted?
Open BOTH valves on the manifold and allow the can's contents to be directly exposed to both ports. Allow equilibrium to be reached. Both gauges should read the same, roughly static pressure based on your local ambient temp. If they don't, you have a problem with the manifold gauge set.
But doesn't the fact that very little can go into the system point to some sort of restriction?
BTW, did you flush or blow air through the condenser to verify it's not restricted?
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Did the engine off test. Both sides came up to a little over 70 psi. Closed off both lines, started engine and turned ac on. Compressor engaged for a brief second then shut off continually. The pressure on the high side would rise to about 110 but the low side did not move. I turned the can on and opened up the low side. It increased its pressure to about 100, but high side stayed about the same (70 until compressor kicked on, would raise then drop back down when compressor turned off) and the compressor still briefly engaging. So I'm assuming restriction between low side and compressor? With a new hose to AC manifold can only think it would be the evaporator or could it still be the condensor? Like I said originally I flushed the evaporator and blew air through, didn't seem restricted. I blew air only through the condensor and air came out, but not as much as the evaporator, I'm assuming because the smaller lines.
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From: St Louis
I turned the can on and opened up the low side. It increased its pressure to about 100, but high side stayed about the same (70 until compressor kicked on, would raise then drop back down when compressor turned off) and the compressor still briefly engaging.
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Shouldnt the low side drop when the compressor is on though? It was going for about 20 minutes and took less than half a can.
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From: St Louis
You might have a bad valve on the low side of your manifold connection. You have to turn the valve off from the supply (can) in order to see the low side pressure drop when the compressor engages. Otherwise, what you are seeing is the can's pressure which, due to its proximity to the gauge relative to the suction port of the compressor, is basically right on top of the gauge.
More patience while charging.........
Put the can in a bucket of HOT water, it will speed things up.. unless you feel lucky and want to try tipping the can and sucking in liquid which runs the risk of compressor damage. Those are the only ways you're going to speed up the process.
More patience while charging.........
Put the can in a bucket of HOT water, it will speed things up.. unless you feel lucky and want to try tipping the can and sucking in liquid which runs the risk of compressor damage. Those are the only ways you're going to speed up the process.
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You might have a bad valve on the low side of your manifold connection. You have to turn the valve off from the supply (can) in order to see the low side pressure drop when the compressor engages. Otherwise, what you are seeing is the can's pressure which, due to its proximity to the gauge relative to the suction port of the compressor, is basically right on top of the gauge.
More patience while charging.........
Put the can in a bucket of HOT water, it will speed things up.. unless you feel lucky and want to try tipping the can and sucking in liquid which runs the risk of compressor damage. Those are the only ways you're going to speed up the process.
More patience while charging.........
Put the can in a bucket of HOT water, it will speed things up.. unless you feel lucky and want to try tipping the can and sucking in liquid which runs the risk of compressor damage. Those are the only ways you're going to speed up the process.