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Car info: US 1999 911 Carrera 2 coupe, 6mt

 

Hello all, I bought a '99 c2 last summer that unfortunately does not have working air conditioning. This summer, after all the hot miserable drives, I've decided to put some time into trying to fix and troubleshoot the system. I've been going through all the common issues and scouring various internet threads and am at the end of my expertise, and wondering if anyone has any ideas (or good independent shop recommendations!) of what else I should check. 

 

As of now, when I engage the ac system, the compressor clicks on just fine. I tried recharging the system late last summer, and it didn't really need any refrigerant, so given that the system still kicks on almost a year later probably rules out any leaks. I've checked the relevant fuses (E7 and D6 I believe) and both are fine. I checked in the passenger's side footwell, and the servo for the mixing flap works fine and the flap also seems to work.

 

Referencing this picture from pelican parts:

pic02.jpg

 

When running the AC for a while, the line with the green arrow grows cool to the touch, but only by a few degrees cooler than ambient. The larger line by the yellow arrow is at ambient temperature if not a few degrees warmer. Both lines coming off the back into the cabin are ambient temperature as well.

 

I have noticed that like many other 996s, mine also has quite a bit of foam debris in the vents, but from all I've read this only effects the heating system, correct me if I'm wrong. 

 

I appreciate the input, hopefully my 996 does not continue to be a slow cooker!

 

 

Edited by Loren
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BM,

 

When you say the A/C kicks in what does mean...  The first thing I would check is to be sure the clutch on your compessor is engaging,  Stick your head under the back bumper close to the A/C compressor then have someone turn the A/C on...  You should hear the pulley coming together with the clutch plate.  Also, if it's working you can no longer turn the clutch plate..

 

And you're sure that you have the correct amount of Fregon, I believe our system takes 1.9 lbs. of R134 Freon... Also, it's good to include the year and model of your car.  There's a lot of posting on the blowing insulation.  I have it and it doesn't seem to have  made any difference.

 

I share your frustration as I have a delayed start with my A/C after a cold start of about 5-10 minutes, once the car is warm up the A/C fires right off...  I'm sure you'll get some good

input from the other members...

 

Good luck and Welcome

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Thanks for the reply, I edited my car info into the first post.

 

When I say the clutch clicks on, as soon as I turn the AC on from the climate controls, the clutch engages on the compressor and spins as it should. From what I've heard, this will only happen if the relay is working correctly and if the system detects an adequate amount of refrigerant, which is why I assumed that I have enough. I do not have the equipment to check how much refrigerant is in the system, so unfortunately I can't answer confidently how much is present or the pressure in the system. 

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It sounds like all the major stuff is working.  At this point I would take it to an AC shop with the proper equipment to vacuum all refrigerant, flush the system with nitrogen,  and recharge the system with the proper amount and type of refrigerant and oil. Question - when you turn the AC on do both of your radiator fans turn on low?

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Thanks for the reply Joe. I'll have to check on the radiator fan switching, I'll take it out for a drive this afternoon and play around with that a bit. When I was flipping switches yesterday I could hear the radiator fans running when the AC compressor was on, that may have been it.

 

I also think it might be time to have some professional eyes check this out as I am out of ideas. Driving in 90+ and humid weather with only windows down gets old fast. If I do, I will post here with what they find. Hoping it's not something with the dreaded 'black box'.

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Sure would get old fast.  I'm in Florida and cannot live without AC.  What is the dreaded "black box"?  From what you described it seems all the AC system components are okay, thus recommending having an AC specialist give it an all out refresh of the refrigerant.  Sounds like you might be low.  Most of the time the "recharge" cans from the auto 

store just don't work to push more refrigerant in the system.

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From what I've seen it's a pretty general term for the HVAC box under the dash. Apparently almost all the parts contained in it cannot be bought individually, or even viewed in most part diagrams.. and it's a pretty complicated system, so if something goes wrong in there, sourcing a new one, replacement used part, or any single part is nearly impossible. As they say though, start with the easy/simple stuff first and work your way through, and getting my refrigerant checked or flushed is what I probably should've checked first.

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22 hours ago, BM_ said:

From what I've seen it's a pretty general term for the HVAC box under the dash. Apparently almost all the parts contained in it cannot be bought individually, or even viewed in most part diagrams.. and it's a pretty complicated system, so if something goes wrong in there, sourcing a new one, replacement used part, or any single part is nearly impossible. As they say though, start with the easy/simple stuff first and work your way through, and getting my refrigerant checked or flushed is what I probably should've checked first.

 

Every part in the HVAC system is available separately: 

 

spacer.png

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There you go, glad I was wrong about that one. Still hoping it's nothing in there as I don't want to pull my dash apart to get at it. Have yet to check the refrigerant but will report back with anything new.

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Sorry if this is a double post.

If there are debris coming from ventilation your HVAC flaps are not functioning as they should. It cant prevent hot air getting to ventilation. So only way is to remove old coating  (what is left) and coat them with proper aluminium tape. Herei is DIY:

 I have done this my car, and it works.

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Some new developments today. I have not taken the car in yet because I was waiting on an AC pressure gauge set so I could see the pressure levels on the high and low side, and see if the expansion valve is working like it should.

 

I tapped into the system and ran the AC for a bit, and the low side was at a pretty steady 32-33 psi, while the high side was only at about 35 psi. The ambient temperature when I ran the test was about 70 degrees F.

 

This seems incredibly low for the high side, would this be from low refrigerant or a bad expansion valve?

 

Another interesting thing, when I sprayed the sensing disc with dust off to frost it up, the high side pressure went up about 35-40 psi to about 70 psi. From what I've seen, the high side pressure should decrease about that amount when running that test, which leads me to believe that maybe the expansion valve is toast? Or maybe the compressor is bad, and it isn't compressing the gas to the appropriate pressure? Or maybe it's just bad/low refrigerant.. I don't know.  I'll update with what I find when I take it into a shop later.

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