Inconsistent air conditioning after refresh
#1
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Thread Starter
Inconsistent air conditioning after refresh
On my recent roadtrip in my 88 S4 with rear AC from Portland āSpokane āPortland I noticed some inconsistent cooling in my air conditioning system. The symptoms are it will blow very cold for a while and then blow cool to warm and then cold. This cycle will take about 10min.
If I turn off the AC and turn it on after a few minutes, I get cold again. The problem seems to get worse at the outside temp goes up. A couple other observations: the problem is worse if I don’t use the rear AC. I get really cold air if the car has not been driven for a while. I get more consistent cooling not in direct sunlight.
Any thoughts?
- My initial thought was the evaporator is freezing/thawing because of the cold/warm cycling. But I am not familiar with the symptoms.
- When I had the system serviced, I don’t think the tech turned on the rear AC (opened the solenoid) when they ran the service, could that have affected the evac/charge?
Background on tests and recent work:
If I turn off the AC and turn it on after a few minutes, I get cold again. The problem seems to get worse at the outside temp goes up. A couple other observations: the problem is worse if I don’t use the rear AC. I get really cold air if the car has not been driven for a while. I get more consistent cooling not in direct sunlight.
Any thoughts?
- My initial thought was the evaporator is freezing/thawing because of the cold/warm cycling. But I am not familiar with the symptoms.
- When I had the system serviced, I don’t think the tech turned on the rear AC (opened the solenoid) when they ran the service, could that have affected the evac/charge?
Background on tests and recent work:
- April 15: AC service vacuum and Pressure tested and fresh 134a refrigerant and cold temp verified at 35-degress F. from center vent.
- April 15: AC refresh: Replaced ALL seals, Rebuilt compressor seals, new barrier hoses, new expansion valves, and receiver/drier.
- April 25: Successfully tested heather valve (all metal), vacuum actuators and solenoids, setting flaps and motor.
- May 14: Verified the heater valve is closed when the AC is on at the lowest temp. Verified the setting motor is not moving while the AC cooling temp is changing.
- PO did the HVAC Compressor relay mod
Last edited by Michael Benno; 05-16-2018 at 04:05 PM.
#2
Rennlist Member
Icing of the evaporator,
35c vent air _IS_ admirable, but in high humidity environments you will develop ice more than in lower ones.
My car will ice up on a drive thru SanFran in evenings in the foggy districts...but when I climb above the fog, its gone.
You can...adjust this, shoot for a few more degrees at the vent..35d vent suggests a 20d evaporator.
35c vent air _IS_ admirable, but in high humidity environments you will develop ice more than in lower ones.
My car will ice up on a drive thru SanFran in evenings in the foggy districts...but when I climb above the fog, its gone.
You can...adjust this, shoot for a few more degrees at the vent..35d vent suggests a 20d evaporator.
#3
Rennlist Member
Relay in the head unit may be going south- most of them are past their sell by date now. Mine was doing something similar albeit somewhat hotter over here.
If that is the case the possible solutions are a rebuilt unit, change out the relay yourself or possibly use the signal to trigger an extra relay with a fused power supply from the hot post to the compressor solenoid.
If that is the case the possible solutions are a rebuilt unit, change out the relay yourself or possibly use the signal to trigger an extra relay with a fused power supply from the hot post to the compressor solenoid.
#4
Rennlist Member
Thread Starter
Relay in the head unit may be going south- most of them are past their sell by date now. Mine was doing something similar albeit somewhat hotter over here.
If that is the case the possible solutions are a rebuilt unit, change out the relay yourself or possibly use the signal to trigger an extra relay with a fused power supply from the hot post to the compressor solenoid.
If that is the case the possible solutions are a rebuilt unit, change out the relay yourself or possibly use the signal to trigger an extra relay with a fused power supply from the hot post to the compressor solenoid.
Last edited by Michael Benno; 05-18-2018 at 11:11 AM.
#5
Rennlist Member
Thread Starter
Icing of the evaporator,
35c vent air _IS_ admirable, but in high humidity environments you will develop ice more than in lower ones.
My car will ice up on a drive thru SanFran in evenings in the foggy districts...but when I climb above the fog, its gone.
You can...adjust this, shoot for a few more degrees at the vent..35d vent suggests a 20d evaporator.
35c vent air _IS_ admirable, but in high humidity environments you will develop ice more than in lower ones.
My car will ice up on a drive thru SanFran in evenings in the foggy districts...but when I climb above the fog, its gone.
You can...adjust this, shoot for a few more degrees at the vent..35d vent suggests a 20d evaporator.
#7
Rennlist Member
Good luck,
Dave
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#11
Team Owner
the freeze switch failed in my 88 S4,
the same symptoms as what the OP reported were also going on in my car,
a new freeze switch and its working fine now.
The WSM says they can be adjusted ,
but IMHO its better to just swap in a new part
the same symptoms as what the OP reported were also going on in my car,
a new freeze switch and its working fine now.
The WSM says they can be adjusted ,
but IMHO its better to just swap in a new part
#12
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Thread Starter
Is there any way to bench rest the temp switch?
#13
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Put an ohmmeter on the contacts. It should read 0 ohms. Put the sensor in ice with a little water. It should read infinity in less than a minute.
Remove from water and it should go back to 0 ohms in a few seconds.
Remove from water and it should go back to 0 ohms in a few seconds.
#14
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Thread Starter
Exellent thanks👍
#15
Rennlist Member
Thread Starter
Is there one for the rear ac too? I didnt see one in pet
EDIT, after thinking about it I realized the freezer was colder than 32-degrees. So I decided to adjust the switch. Turns out the capillary tube/probe was fine. The switch was just triggering at 29-degrees. I was able to adjust it to trigger at 33-degrees.
Last edited by Michael Benno; 06-07-2018 at 02:28 PM.