Vacuum evacuate with rear AC?
#1
Three Wheelin'
Thread Starter
Vacuum evacuate with rear AC?
soon to be vacuuming down my AC system and wonder if I have to leave the key on to make certain that
the rear AC solenoid is energized? if there is no power to solenoid, that line won't be open and might impede draw down?
the rear AC solenoid is energized? if there is no power to solenoid, that line won't be open and might impede draw down?
Last edited by dr bob; 04-01-2019 at 11:44 PM. Reason: Spelling in title
#2
Rennlist Member
Makes no difference to pulling a vacuum as the rear a/c is open to both sides of the compressor. Whether or not some residual lube oil may get stagnated in there is another matter.but should be of little consequence. The solenoid simply prevents circulation around the rear sub circuit.
#3
Three Wheelin'
Thread Starter
#4
Rennlist Member
ONE side wont.
But the other side is.
Both sides are "separate" as far as function, but are connected all the same.
With that valve closed, they are still connected via the compressor.
Do you have a WSM?
But the other side is.
Both sides are "separate" as far as function, but are connected all the same.
With that valve closed, they are still connected via the compressor.
Do you have a WSM?
#5
Rennlist Member
The rear a/c system is simply an additional parallel path to an evaporator- a single block valve in that circuit renders it inoperative. The system performance is limited by condenser capacity so when the rear a/c is working one gets less performance from the front evaporator when the system is on its limit which roughly speaking occurs when the ambient temperature is in the region of 38C to 40C thus why I rarely use the rear a/c.
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#9
Former Vendor
In a perfect 928, there is no need to open the rear control valve by turning on the key and the rear A/C.
Unfortunately, I very rarely get to see these perfect cars. As a matter of fact, these "perfect cars" are few and far between!
Most of the cars I get to see have had the A/C system filled 10-15 times, over the years, with most "techs" adding some oil...."just in case" the system is low on oil.
Consequently, most every system I see is way overfilled with oil....and systems with excessive oil don't cool very well.
The quick way to tell if the system is significantly overfilled with oil is to remove the two lines, under the car, to the rear A/C (because you need to change the O-rings, anyway.) If these two lines are full of oil there is too much oil in the system....way, way too much.
The other thing which occurs when the lines are full of oil is that the rear part of the A/C system doesn't get evacuated....'cause the lines are blocked with oil.
So, I always pull the lines off, turn the rear system on with the key on, and let things "drain". And when I evacuate, I always evacuate with the rear A/C turned on.....at least part of the time.
Unfortunately, I very rarely get to see these perfect cars. As a matter of fact, these "perfect cars" are few and far between!
Most of the cars I get to see have had the A/C system filled 10-15 times, over the years, with most "techs" adding some oil...."just in case" the system is low on oil.
Consequently, most every system I see is way overfilled with oil....and systems with excessive oil don't cool very well.
The quick way to tell if the system is significantly overfilled with oil is to remove the two lines, under the car, to the rear A/C (because you need to change the O-rings, anyway.) If these two lines are full of oil there is too much oil in the system....way, way too much.
The other thing which occurs when the lines are full of oil is that the rear part of the A/C system doesn't get evacuated....'cause the lines are blocked with oil.
So, I always pull the lines off, turn the rear system on with the key on, and let things "drain". And when I evacuate, I always evacuate with the rear A/C turned on.....at least part of the time.