ac question on S4
07-01-2005, 03:43 PM
#1
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ac question on S4
ok... ac was working, then I got like a "fog" coming out of the vents and now it's no longer cold... before I go spending $$$ on this what can I check
mind you I'm not an electrical guru or hvac kind of person so everyday language is appreciated
the fuse is fine, the compressor does kick on and the ac light is on... rear ac is off but it doesn't get cold either
mind you I'm not an electrical guru or hvac kind of person so everyday language is appreciated
the fuse is fine, the compressor does kick on and the ac light is on... rear ac is off but it doesn't get cold either
07-01-2005, 04:40 PM
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You could simply be low on freon. I'm no expert either but if you look at the sight glass on top of the dryer (front passenger side) you should see a few bubbles passing through the system when the compressor is on. Too many bubbles you are low on freon. I think what happens is when freon is low the preasure of the system is down causing the air in the system to expand and become visible (kinda like opening a soda) The air then freezes when it is atomized and causes the cooling coil to freeze and your vents will blow smoke because of the ice. Again this is just my theory on how the system works and what could be wrong. I'm sure there is an expert out there that will be able to help more.
07-01-2005, 04:53 PM
#4
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Start out with a simple test of expansion valve function. Very tough test, where you run the AC and see if the pressure line between the expansion valve and the evaporator gets cold. Open the hood, lift the rain shield, two fingers of right hand on the expansion valve, move fingers to line that runs toward the cabin... Is it cold?
beg/borrow/steal (or just buy...) a set of refrigeration gauges. Confirm that there is really some freon left in the system before you run it a lot this way. The pressure switch is a sefety net that protects the compressor, but they sometimes fail. There are also owners who have discovered tthat the switch can be bypassed with a jumper to force the compressor to run without a sufficient freon charge. Nobody we know would ever do anything like that, right? I've seen it a few times. Anyway, the gauges will confirm that there is or isn't gas in the system, and whether the compressor is actually compressing.
The "fog" is a possible telltale: The system actually has the potential to be coldest when the suction pressure is lowest. Same as "low on freon" But it also depends on the total heat load on the system, so this is not a way to run the car. Low freon charge also means low oil circulation, a cause of slow lingering death to compressors.
So, check the charge with the gauges, confirm that the compressor is compressing with the gauges, after doing the basic 'is it flowing freon?' test with the fingers.
beg/borrow/steal (or just buy...) a set of refrigeration gauges. Confirm that there is really some freon left in the system before you run it a lot this way. The pressure switch is a sefety net that protects the compressor, but they sometimes fail. There are also owners who have discovered tthat the switch can be bypassed with a jumper to force the compressor to run without a sufficient freon charge. Nobody we know would ever do anything like that, right? I've seen it a few times. Anyway, the gauges will confirm that there is or isn't gas in the system, and whether the compressor is actually compressing.
The "fog" is a possible telltale: The system actually has the potential to be coldest when the suction pressure is lowest. Same as "low on freon" But it also depends on the total heat load on the system, so this is not a way to run the car. Low freon charge also means low oil circulation, a cause of slow lingering death to compressors.
So, check the charge with the gauges, confirm that the compressor is compressing with the gauges, after doing the basic 'is it flowing freon?' test with the fingers.
07-01-2005, 05:04 PM
#5
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Rixter,
Go to Wally's world on the 928 specialists web site and get the writeup on HVAC that Wally P did.
It helps you trouble shoot the whole system.
Roger
Go to Wally's world on the 928 specialists web site and get the writeup on HVAC that Wally P did.
It helps you trouble shoot the whole system.
Roger
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
07-01-2005, 05:08 PM
#6
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Originally Posted by dr bob
Start out with a simple test of expansion valve function. Very tough test, where you run the AC and see if the pressure line between the expansion valve and the evaporator gets cold. Open the hood, lift the rain shield, two fingers of right hand on the expansion valve, move fingers to line that runs toward the cabin... Is it cold?
beg/borrow/steal (or just buy...) a set of refrigeration gauges. Confirm that there is really some freon left in the system before you run it a lot this way. The pressure switch is a sefety net that protects the compressor, but they sometimes fail. There are also owners who have discovered tthat the switch can be bypassed with a jumper to force the compressor to run without a sufficient freon charge. Nobody we know would ever do anything like that, right? I've seen it a few times. Anyway, the gauges will confirm that there is or isn't gas in the system, and whether the compressor is actually compressing.
The "fog" is a possible telltale: The system actually has the potential to be coldest when the suction pressure is lowest. Same as "low on freon" But it also depends on the total heat load on the system, so this is not a way to run the car. Low freon charge also means low oil circulation, a cause of slow lingering death to compressors.
So, check the charge with the gauges, confirm that the compressor is compressing with the gauges, after doing the basic 'is it flowing freon?' test with the fingers.
beg/borrow/steal (or just buy...) a set of refrigeration gauges. Confirm that there is really some freon left in the system before you run it a lot this way. The pressure switch is a sefety net that protects the compressor, but they sometimes fail. There are also owners who have discovered tthat the switch can be bypassed with a jumper to force the compressor to run without a sufficient freon charge. Nobody we know would ever do anything like that, right? I've seen it a few times. Anyway, the gauges will confirm that there is or isn't gas in the system, and whether the compressor is actually compressing.
The "fog" is a possible telltale: The system actually has the potential to be coldest when the suction pressure is lowest. Same as "low on freon" But it also depends on the total heat load on the system, so this is not a way to run the car. Low freon charge also means low oil circulation, a cause of slow lingering death to compressors.
So, check the charge with the gauges, confirm that the compressor is compressing with the gauges, after doing the basic 'is it flowing freon?' test with the fingers.
not sure of the line you are talking about but nothing under the shield gets cold
I'm at home today but we have gauges at the shop
the ac WAS ICE FREAKIN COLD prior to the "fog" and subsequent non-cold condition... I actually had to turn it off to keep from freezing
will check w/gauges this weekend, and I won't use the ac until I figure it out...
07-01-2005, 05:26 PM
#7
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ok.. got Wally's writeup (thanks Roger) and now have a couple questions (excuse me I'm a newbie on this one but I WILL LEARN THIS)
under the shield, is this the line that should be cold?
this is one connector I found for ac, it says IN on it.. is this lowside?
and where is the other connector? I can't find it anywhere...
thanks folks
under the shield, is this the line that should be cold?
this is one connector I found for ac, it says IN on it.. is this lowside?
and where is the other connector? I can't find it anywhere...
thanks folks
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07-01-2005, 05:35 PM
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Rixter,
The expansion valve is to the left of your red mark and the pipe you are looking for runs into that.
You should also feel cold from the expansion valve as well as the pipe going into it.
The other connection is on the passenger side on the pipe below the battery terminal post.
It is well hidden so as to make it hard for us to find.
Hope that helps.
Roger
The expansion valve is to the left of your red mark and the pipe you are looking for runs into that.
You should also feel cold from the expansion valve as well as the pipe going into it.
The other connection is on the passenger side on the pipe below the battery terminal post.
It is well hidden so as to make it hard for us to find.
Hope that helps.
Roger
07-01-2005, 05:38 PM
#9
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thanks Roger,
so in pic#2 is that the high side or low side?
is this where I would add refrigerant? or do I add at the other one under the post?
so in pic#2 is that the high side or low side?
is this where I would add refrigerant? or do I add at the other one under the post?
07-01-2005, 05:49 PM
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High side.
Add to the other connection.
If you look in the WSM there is a great writeup on how to check the performance once you have it topped up.
Is it R12 or R134a?
Add to the other connection.
If you look in the WSM there is a great writeup on how to check the performance once you have it topped up.
Is it R12 or R134a?
07-01-2005, 05:52 PM
#11
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it had something done to it in '99 that included some marked type of coolant so I'm not sure... I'd like to find this other freakin connection!!!
I read thru most of the WSM deal and got lost... and that big **** contraption for checking things kinda threw me for a loop
I read thru most of the WSM deal and got lost... and that big **** contraption for checking things kinda threw me for a loop
07-01-2005, 05:59 PM
#12
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FOUND IT!!! damn that's in a tight spot... don't know if I can even get a gauge on it..
neighbor has gauges so gonna try it
thanks Roger
neighbor has gauges so gonna try it
thanks Roger
07-01-2005, 08:31 PM
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It sounds like you had some type of sudden leak, causing a loss of coolant & a corresponding loss of cold air.... Since you found both the low & high connections, I'm guessing that they will read low... BUT before you start adding coolant (especially expensive R12) you should take it to a shop (or find someone who has an A/C vaccuum pump) and have the system vaccuumed down to check for leaks. I had a slow leak in the low pressure line, eventually enough coolant will leak out and trip the low pressure switch...since your compressor is still running, it hasn't got that low OR the switch isn't working? It is odd that it went from working well to hardly working at all instantly?
Brian
It sounds like you had some type of sudden leak, causing a loss of coolant & a corresponding loss of cold air.... Since you found both the low & high connections, I'm guessing that they will read low... BUT before you start adding coolant (especially expensive R12) you should take it to a shop (or find someone who has an A/C vaccuum pump) and have the system vaccuumed down to check for leaks. I had a slow leak in the low pressure line, eventually enough coolant will leak out and trip the low pressure switch...since your compressor is still running, it hasn't got that low OR the switch isn't working? It is odd that it went from working well to hardly working at all instantly?
Brian
07-01-2005, 08:47 PM
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I've had the car for a month.. it worked well on way to SITM then got ice cold.. worked so so on the way home from there, was off road for 2.5 weeks while I did the tb/wp, in the last week would start working fine then the start of the "fog" and now no cold air
I believe it was low when I got it as it was really cold, and this isn't a sudden loss of all the refrigerant
I can't get the neighbors gauge on so tomorrow I'm gonna have to find a way to get the nipple turned to an angle I can get the gauge on and go from there.. right now it's at an angle directly facing the dist
I believe it was low when I got it as it was really cold, and this isn't a sudden loss of all the refrigerant
I can't get the neighbors gauge on so tomorrow I'm gonna have to find a way to get the nipple turned to an angle I can get the gauge on and go from there.. right now it's at an angle directly facing the dist