AC system pressure problems
05-25-2020, 10:37 PM
#1
Newbie
Thread Starter
AC system pressure problems
Hello everyone. Today I got the chance to work on the Pastor's 2001 430 CLK. The vehicle has not had any form of cool, or even luke warm for that matter, air since he purchased it last year.
I connected the gauge manifold set and observed the initial static pressure which was 60 psi LOW and 60 psi HIGH. I started the engine and the readings did not change. The clutch on the front of the compressor was engaged with the compressor, but the gauge still only read 60/60. According to the Nissen cheat sheet I downloaded, it looks like a possible defective AC compressor or a MCV or an ECV failure that is causing poor suction pressure. One of my problems is that I don't know what these valves are OR if they are even part of the AC system on this 430 CLK. I know there is an expansion valve that I thought could have been the problem, but the cheat sheet does not give a hint that this component could be bad... unless of course that is what the MCV or ECV thingies are.
I haven't looked for the expansion valve yet on this car, but is it easy enough to get to? I have heard a few mechanic's speak that the AC compressor was fairly easy enough to replace.
On his 1990 420 SEL, I discovered a totally different scenario with the pressures. With the engine running, I had a NEGATIVE -10 psi on the low side and a high side pressure of around 50 psi. Cannot remember exactly the sequence of events, but the pressure ultimately made it to 60/60 psi running. Oh yeah, no clutch engagement on this one and no movement with the add of refrigerant.
I would appreciate any thoughts on either of these or both and I hope everyone has a wonderful week ahead.
I connected the gauge manifold set and observed the initial static pressure which was 60 psi LOW and 60 psi HIGH. I started the engine and the readings did not change. The clutch on the front of the compressor was engaged with the compressor, but the gauge still only read 60/60. According to the Nissen cheat sheet I downloaded, it looks like a possible defective AC compressor or a MCV or an ECV failure that is causing poor suction pressure. One of my problems is that I don't know what these valves are OR if they are even part of the AC system on this 430 CLK. I know there is an expansion valve that I thought could have been the problem, but the cheat sheet does not give a hint that this component could be bad... unless of course that is what the MCV or ECV thingies are.
I haven't looked for the expansion valve yet on this car, but is it easy enough to get to? I have heard a few mechanic's speak that the AC compressor was fairly easy enough to replace.
On his 1990 420 SEL, I discovered a totally different scenario with the pressures. With the engine running, I had a NEGATIVE -10 psi on the low side and a high side pressure of around 50 psi. Cannot remember exactly the sequence of events, but the pressure ultimately made it to 60/60 psi running. Oh yeah, no clutch engagement on this one and no movement with the add of refrigerant.
I would appreciate any thoughts on either of these or both and I hope everyone has a wonderful week ahead.
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michaelwoosley (05-27-2020)
05-27-2020, 01:47 PM
#3
Newbie
Thread Starter
Plutoe, I dispensed plenty of refrigerant into the system... when I entered the diagnostic system, I monitored code 7 and based off a previous post, I dispensed enough R134 to get the reading to to 5 bar (the compressor clutch had not kicked on yet), so I dispensed more to 6 bar and the clutch engaged. Still at this point, we still did not have any cool air; only hot blowing air at the vents. Also, note, I did not have the gauge set at this time. Once I got to 7 bar on the display, I stopped.
A few days ago, I actually hooked up the gauge/manifold set and observed the 60 psi low side/60 psi high side readings. This led me to believe, based off the Nissen cheat sheet, that either the compressor was bad, or the MCV or the ECV (whatever those are) were faulty or malfunctioning.
At this point, I want to tell the Pastor that I believe his compressor is faulty and that I can replace it, the expansion valve, receiver/dryer and condenser unit and then add oil and recharge the system.
Am I far off from making a correct assumption? I will tell him that I cannot guarantee that replacing these components will fix his problem, but geez, the only thing that I wouldn't be replacing in his system would be the evaporator core. It looks like his AC control unit is working fine as I can pull up his codes, erase the codes and read his data without any problems.
A few days ago, I actually hooked up the gauge/manifold set and observed the 60 psi low side/60 psi high side readings. This led me to believe, based off the Nissen cheat sheet, that either the compressor was bad, or the MCV or the ECV (whatever those are) were faulty or malfunctioning.
At this point, I want to tell the Pastor that I believe his compressor is faulty and that I can replace it, the expansion valve, receiver/dryer and condenser unit and then add oil and recharge the system.
Am I far off from making a correct assumption? I will tell him that I cannot guarantee that replacing these components will fix his problem, but geez, the only thing that I wouldn't be replacing in his system would be the evaporator core. It looks like his AC control unit is working fine as I can pull up his codes, erase the codes and read his data without any problems.
05-29-2020, 07:11 AM
#5
Super Member
not sure if you are reading the AC fault codes...compressor will not run if fault code present
Turn the ignition on, which starts a 20 second timer.
Increase the left side temperature (left red arrow) until left side says “HI” and decrease the right side temperature (right cold arrow) until right side says “LO.” If 20 seconds has passed, switch off the ignition and switch it back on. Your HI/LO settings will be preset. The timer will restart.
Press and hold the “EC” and “REST” buttons simultaneously for at least five seconds.
The screen will go blank. At this point you can forget about the 20 second timer because you are now in diagnostic mode.
Load the first code by pressing the right side “AUTO” button.
If you have any error codes in memory, the screen will show them. On the screen, ‘E’ stands for “error.” If you’ve never done this before, every code the system has logged since it was last cleared will still be present – whether the problem has been repaired or not. You should write down each error code. To list each of the codes, just press the right side “AUTO” button. After writing them all down, I would clear the codes, turn the car off and on, use the AC and see if any codes come back. If they do, the code points to a problem. To clear the codes, press both AUTO¯ switches simultaneously for more than 5 seconds while in diagnostic mode. When the codes are cleared you will see display change to "d and FF". After you turn the ignition switch off, all the codes will be erased.
Turn the ignition on, which starts a 20 second timer.
Increase the left side temperature (left red arrow) until left side says “HI” and decrease the right side temperature (right cold arrow) until right side says “LO.” If 20 seconds has passed, switch off the ignition and switch it back on. Your HI/LO settings will be preset. The timer will restart.
Press and hold the “EC” and “REST” buttons simultaneously for at least five seconds.
The screen will go blank. At this point you can forget about the 20 second timer because you are now in diagnostic mode.
Load the first code by pressing the right side “AUTO” button.
If you have any error codes in memory, the screen will show them. On the screen, ‘E’ stands for “error.” If you’ve never done this before, every code the system has logged since it was last cleared will still be present – whether the problem has been repaired or not. You should write down each error code. To list each of the codes, just press the right side “AUTO” button. After writing them all down, I would clear the codes, turn the car off and on, use the AC and see if any codes come back. If they do, the code points to a problem. To clear the codes, press both AUTO¯ switches simultaneously for more than 5 seconds while in diagnostic mode. When the codes are cleared you will see display change to "d and FF". After you turn the ignition switch off, all the codes will be erased.
