A/C Trouble in the Desert...
07-09-2016, 09:43 PM
#1
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A/C Trouble in the Desert...
Hey Guys,
First time poster here. I acquired my 86.5 928 5 speed about 2 months ago. It's my only car right now...so say what you will about that
. Anyway, I am in the sweltering heat of the Arizona desert for the summer. It's always garaged at night and parked in the shade at work.
On to the issue, the A/C has been very hit or miss since ownership. at first it was ok so I took it to the local shop and they recharged it and gave it a clean bill of health. About a week later though it turns on and off. If I let the car sit overnight and get in it in the morning the ac runs great. However, if I turn the car off or it stalls (another issue) the a/c is out for the rest of the day until it sits overnight again.
On top of this intermittent a/c, when it is on the car is very loaded up. anytime the clutch goes in the rpms dip severely sometimes to point of stalling. It only does this when the AC is on. I've been told to check to see if the compressor clutch is engaging but i'm not sure the best way to do this. I opened the hood and verified the compressor wheel is spinning but I'm not sure what to look for past that.
Any help would be greatly appreciated. It's hot as **** and I'm new to these cars. Thanks very much
First time poster here. I acquired my 86.5 928 5 speed about 2 months ago. It's my only car right now...so say what you will about that
. Anyway, I am in the sweltering heat of the Arizona desert for the summer. It's always garaged at night and parked in the shade at work.On to the issue, the A/C has been very hit or miss since ownership. at first it was ok so I took it to the local shop and they recharged it and gave it a clean bill of health. About a week later though it turns on and off. If I let the car sit overnight and get in it in the morning the ac runs great. However, if I turn the car off or it stalls (another issue) the a/c is out for the rest of the day until it sits overnight again.
On top of this intermittent a/c, when it is on the car is very loaded up. anytime the clutch goes in the rpms dip severely sometimes to point of stalling. It only does this when the AC is on. I've been told to check to see if the compressor clutch is engaging but i'm not sure the best way to do this. I opened the hood and verified the compressor wheel is spinning but I'm not sure what to look for past that.
Any help would be greatly appreciated. It's hot as **** and I'm new to these cars. Thanks very much
07-09-2016, 10:10 PM
#2
Vegas, Baby!
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Chris, use the search function at the top of the page. Lots of info and fix's. I'm in Vegas and it's hot here too!
One of the first things I'd check is the heater valve. When these cars are off the heater valve opens upon loss of vacuum. Means you've got the heater running with the A/C on too.
Search is you're friend on this forum. Good luck.
One of the first things I'd check is the heater valve. When these cars are off the heater valve opens upon loss of vacuum. Means you've got the heater running with the A/C on too.
Search is you're friend on this forum. Good luck.
07-09-2016, 11:08 PM
#3
Rennlist Member
A/C = alchemy. There is a ton of stuff here on the system, but if you aren't prepared to tackle it, you will go nuts. Is it R12? Just to start you need gauges and a leak detector.
RE the clutch: With a helper, hood up, you listen when the helper turns the A/C on, you should be able to hear it engage, click. When on, the inner part of the pulley will turn continuously, but that doesn't mean it is compressing. Beyond that you really need to be able to trace it electrically which means doing your homework.
Most likely there is a leak. If it only held for 2 weeks, it is a big one; big or small, you need for the shop to fix it or refund your money. If they are reputable, they should be able to diagnose and explain it to you. It could get expensive, because some of the seals are in most difficult places. If all they can do is flush and recharge, you need to find another shop or start buying equipment, which most of us don't want to do. Good luck.
RE the clutch: With a helper, hood up, you listen when the helper turns the A/C on, you should be able to hear it engage, click. When on, the inner part of the pulley will turn continuously, but that doesn't mean it is compressing. Beyond that you really need to be able to trace it electrically which means doing your homework.
Most likely there is a leak. If it only held for 2 weeks, it is a big one; big or small, you need for the shop to fix it or refund your money. If they are reputable, they should be able to diagnose and explain it to you. It could get expensive, because some of the seals are in most difficult places. If all they can do is flush and recharge, you need to find another shop or start buying equipment, which most of us don't want to do. Good luck.
07-10-2016, 10:04 AM
#4
Rennlist Member
A clean bill of health from your service guys means only that it is working great right now; and apparently it is and has been off and on since. With a 30 year old car, and likely the same age on most about everything on it, I suspect your AC compressor is going out. Seizing up when it is hot then working after it cools overnight is why that comes to mind.
07-10-2016, 11:09 AM
#5
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Sounds like the high pressure limit switch to me. If the pressure in the system gets too high, which it will after running for a while, or heat soaking, the pressure limit switch breaks the connection to the AC clutch disabling the AC from starting. When you are in the failed mode, start the engine, turn on the AC, open the hood, look down the right side of the engine behind the radiator with a flashlight, and see if the AC compressor is spinning by the front of the unit turning with the belt. If so, see below.
As has been mentioned, you need to see that your heater valve isn't sticking open defeating the AC. To test, this, start and warm the car, turn the AC off, set the slider all the way to the cold(blue) side and test the air coming from the vents. If it is noticeably hotter than the air going into the car, then your heater valve is stuck open, or it's failed internally. It will need to be replaced, or the vac actuator needs to be replaced. Best bet is to repl the valve under the filter housing then wire it shut until Nov.
As has been mentioned, you need to see that your heater valve isn't sticking open defeating the AC. To test, this, start and warm the car, turn the AC off, set the slider all the way to the cold(blue) side and test the air coming from the vents. If it is noticeably hotter than the air going into the car, then your heater valve is stuck open, or it's failed internally. It will need to be replaced, or the vac actuator needs to be replaced. Best bet is to repl the valve under the filter housing then wire it shut until Nov.
07-10-2016, 12:34 PM
#6
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On the AC clutch, the only way to be absolutely sure is with gauges. The next best way is to observe the inner assembly rotating. This is the area between the pulley and the shaft on the radiator side of the pulley.
I've see an few clutches that click and appear to move but don't fully engage and even slip. They are after all clutches and subject to wear. When clutch slipping it first starts it will be intermittent, on the hottest days, possibly after a quick blip of the throttle that started the slip and warmed the clutch, reduced AC continues until the AC clutch cools down at which point the system appears to work fine.
Generally all that is needed is adjustment which is done by changing a spacer washer that is on the bolt that runs from the front of the AC Clutch. It is important to have the right feeler gauges as if too small of a spacer is used the AC may engage when it isn't suppose to, and in this situation it is not protected by any of the various safeties, as they only work to engage and disengage the clutch.
For these reasons and a lot of others I recommend that only people well versed in refrigeration systems actually work on the refrigeration side, diagnosing and changing controls one for one, not an issue.
Good luck.
I've see an few clutches that click and appear to move but don't fully engage and even slip. They are after all clutches and subject to wear. When clutch slipping it first starts it will be intermittent, on the hottest days, possibly after a quick blip of the throttle that started the slip and warmed the clutch, reduced AC continues until the AC clutch cools down at which point the system appears to work fine.
Generally all that is needed is adjustment which is done by changing a spacer washer that is on the bolt that runs from the front of the AC Clutch. It is important to have the right feeler gauges as if too small of a spacer is used the AC may engage when it isn't suppose to, and in this situation it is not protected by any of the various safeties, as they only work to engage and disengage the clutch.
For these reasons and a lot of others I recommend that only people well versed in refrigeration systems actually work on the refrigeration side, diagnosing and changing controls one for one, not an issue.
Good luck.
