AC Issue
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AC Issue
2000 Expy 4.6L RWD
OK, so it’s HOT here in Texas. It hit 107 today and it felt like the AC was barely working, so I went to Harbor Freight and got an AC manifold gauge and vacuum pump.
The system pressures is 100psi when the car is off (both high and low side). At 1500RPM with full AC on it’s about 45psi low side and 320psi high side. After some google research it would appear that these pressures are “normal” even a little high.... I put that down to it being so hot.
So my question is: Is the AC just a piece of crud, are the pressures actually low on account of the heat, or is there something else I can check?
As always, thanks for ur help!
OK, so it’s HOT here in Texas. It hit 107 today and it felt like the AC was barely working, so I went to Harbor Freight and got an AC manifold gauge and vacuum pump.
The system pressures is 100psi when the car is off (both high and low side). At 1500RPM with full AC on it’s about 45psi low side and 320psi high side. After some google research it would appear that these pressures are “normal” even a little high.... I put that down to it being so hot.
So my question is: Is the AC just a piece of crud, are the pressures actually low on account of the heat, or is there something else I can check?
As always, thanks for ur help!
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Thanks guys
Jeff. What is the correct tool and proceedure to measure the temperature at the vents?
ProjectSHO89 - The reason I am messing with the AC is that when when you turn on the AC in my wifes Toyota it will freeze ur face off no matter what the temperature is outside. The expy takes over 20 minutes before it even feels like it's working and i want to know why.
Jeff. What is the correct tool and proceedure to measure the temperature at the vents?
ProjectSHO89 - The reason I am messing with the AC is that when when you turn on the AC in my wifes Toyota it will freeze ur face off no matter what the temperature is outside. The expy takes over 20 minutes before it even feels like it's working and i want to know why.
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Jeff
I used a thermocouple attached to my multimeter. Stuck the probe into the vent next to the stereo, turned on max AC and opened all the windows.
Ambient temp is 86F this morning. After a few minutes the vent temp stabilized at 63F. That's 23F lower than ambient. Chiltons says it should be 35 to 40 lower....
What do you think?
I used a thermocouple attached to my multimeter. Stuck the probe into the vent next to the stereo, turned on max AC and opened all the windows.
Ambient temp is 86F this morning. After a few minutes the vent temp stabilized at 63F. That's 23F lower than ambient. Chiltons says it should be 35 to 40 lower....
What do you think?
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Joined: Jan 2004
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From: St Louis
Well, the Toyota does probably have a lot smaller volume of air to condition...... Does the Expy have rear air or is it a front-only system?
Any chance it's overcharged (DIY filling)?
Connect the gauges, do your setup, then mist the condenser with a garden hose while watching both the pressures and the vent temperature.
Any chance it's overcharged (DIY filling)?
Connect the gauges, do your setup, then mist the condenser with a garden hose while watching both the pressures and the vent temperature.
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Thanks guys - First off to answer the questions
Front & rear air con
I've never added any R134a to the system, but who knows what the previous owners did.
Here are my results. Same technique as earlier:
Windows open, max AC probe inside air vent next to stereo
Ambient temp today is 100F
With the car off low and high side read 90psi.
At idle
45psi low side
260psi high
73F inside the vent
At 1500RPM the high side pressure shot up.
60 low
375 high
73F vent
Then I "misted" the condenser and took readings at 1 minute intervals
Immediately the high side dropped. I watched the needle swing down as the water hit.
55 low
270 high
72 vent
1 minute later
50 low
250 high
70 vent
1 minute later
50 low
250 high
68 vent
Then it stabilized with those numbers.
I'm looking forward to hearing what you think!
Front & rear air con
I've never added any R134a to the system, but who knows what the previous owners did.
Here are my results. Same technique as earlier:
Windows open, max AC probe inside air vent next to stereo
Ambient temp today is 100F
With the car off low and high side read 90psi.
At idle
45psi low side
260psi high
73F inside the vent
At 1500RPM the high side pressure shot up.
60 low
375 high
73F vent
Then I "misted" the condenser and took readings at 1 minute intervals
Immediately the high side dropped. I watched the needle swing down as the water hit.
55 low
270 high
72 vent
1 minute later
50 low
250 high
70 vent
1 minute later
50 low
250 high
68 vent
Then it stabilized with those numbers.
I'm looking forward to hearing what you think!
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Thanks for the follow up Jeff
The front and rear vent temperatures feel similar. I didnt measure it. For the test I shut the back off.
The cabin itself stayed like a sauna throughout the test. I had all the windows and one door open.
After spraying the condenser with water i let the AC run for about 5 minutes. The front vent temperature dropped from 73 to 68, then I shut it off so I don't know if it would have kept getting colder or not. It held at 68 for 3 minutes.
Do I need to do a longer test?
Thanks again!
The front and rear vent temperatures feel similar. I didnt measure it. For the test I shut the back off.
The cabin itself stayed like a sauna throughout the test. I had all the windows and one door open.
After spraying the condenser with water i let the AC run for about 5 minutes. The front vent temperature dropped from 73 to 68, then I shut it off so I don't know if it would have kept getting colder or not. It held at 68 for 3 minutes.
Do I need to do a longer test?
Thanks again!
Hotshot
Joined: Jan 2004
Posts: 19,760
Likes: 1,079
From: St Louis
Can't be the expansion valve since he doesn't have one in his system. Ford systems use an orifice tube for the front A/C unit.
That tells me your gauges are inaccurate. At 100F ambient, your static system pressure should read around 125 psi. I see you bought the manifold at Harbor Freight. 'Nuff said.
Your large drop in high side pressure when misted suggests that the condenser is not rejecting enough heat during normal operation. This is most commonly caused by inadequate airflow through the condenser, usually due to either built up junk (bugs, dirt, debris) or a weakened fan clutch.
To determine for certain which side of the firewall a problem is on, compare the relative temperature of the evaporator inlet to the outlet. If they're both cold, within a few degrees of each other, the problem in on the cabin side of the system. If the outlet temperature is substantially higher than the inlet, the problem is on the engine compartment side of the sealed system.
Clean the condenser and get a better set of accurate gauges for now. Avoid the Interdynamics ones, too. When the new gauges take new readings. Check the inlet/outlet temps.
Ambient temp today is 100F
With the car off low and high side read 90psi.
With the car off low and high side read 90psi.
Your large drop in high side pressure when misted suggests that the condenser is not rejecting enough heat during normal operation. This is most commonly caused by inadequate airflow through the condenser, usually due to either built up junk (bugs, dirt, debris) or a weakened fan clutch.
To determine for certain which side of the firewall a problem is on, compare the relative temperature of the evaporator inlet to the outlet. If they're both cold, within a few degrees of each other, the problem in on the cabin side of the system. If the outlet temperature is substantially higher than the inlet, the problem is on the engine compartment side of the sealed system.
Clean the condenser and get a better set of accurate gauges for now. Avoid the Interdynamics ones, too. When the new gauges take new readings. Check the inlet/outlet temps.