993 Azul

96 993 27,000mi,bought past July,suddenly A/c not blowing cold air,before taking it to dealer (170mi )and I've read all posts on a/c and symptons are:
-Max A/c when pressed light comes on but no change in airflow,when releasing switch air flow increases for a nanosecond.
-No condensation under car after running a/c.
-When engaging a/c switch compressor engages but seems it is not recycling.
Sorry for long post but I want to be somewhat knowledgeable before taking it to the stealer and reading all of the posts left me scared of the cost of replacing evaporator.This the greatest forum of all marques and I thank you in advance for any help.
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96 993 Coupe midnight blue/blue-Slippery slope/Turbo 3-spoke wheel,alu/carbon shifter and handbrake,stainless sills,MY 02 996 17" wheels,ultimate pedals.
05 LR3
03 Navigator(wife)
00 BMW Mcoupe{sold last year)
Previous P-car 1979 924 Sebring(I know,I know young and stupid,great handling,lousy terrible engine.

BIG-BRO

I had similar symptoms this year - it turned out just to be a vacuum hose that connects to the CCU in-dash. I had knocked it loose doing some other work. Cold air would just blow for a second and then stop.

I did a search in hte 993 forum here and found several write-ups of how to trace down some of the simple vaccum type control issues.

BS911

Max A/C - in regards to air flow in the cabin - is no different than fan speed of 4 with system selected on recirc mode. I would second Paul's suggestion to look at the vacuum issue on that surge of air. If your vacuum is not engaging the internal air flap, then your recirc mode is cutting off all fresh air and the internal air is not opening. You would simply not be drawing enough air to cool anything. Have you recently had a stereo installed or a dealer working on your car?

Start with this... http://p-car.com/diy/acdiag.html

If your compressor engages and is running without cycling on and off, then that is a good sign. If you aren't getting condensation dripping out it may not necessarily be a bad thing either. How humid is it down there in Brownsville? You might have a clog in the drain below the evaporator which lets it pool up in there a bit if you think you should have cold air, but I would start troubleshooting that until you get cold air back first. Reason being that if the water is building up and not draining, then the problem it would cause is that the evaporator would freeze up. If the evap freezes up then your system will detect it and turn the compressor off.

We have a lot of things to check out before this could turn costly. And I think the fact that your compressor continues to run puts you past several of the costly items already.

993 Azul

Thanks, wouldn't you know it the Max a/c botton started working fine a short
while ago.The airflow is fine in the normal a/c.but no cold air and definetely there is no condensation after turning off and yes Brownsville,Tx is very humid.
When the car is idling with a/c on how often should the compressor recycle?
Could it be low refrigerant?Thanks

993 Azul

Thanks Brian,
How do you go about cleaning drain?
Joseph

rbeggs

Big-Bro,

I have 3 CCU (dash mounted controller) units in front of me and see no evidence of a vacuum hose connection, just the two multi-pin harness connectors. These are PN 993 659 047 01. What am I overlooking? I have the same cold air for several seconds then nada issue.

Thanks, rb

'93 C4S
'62 356B

chet

The vacuum hose doesn't actually attach to the CCU. It is up under the dash sort of behind the CCU and attaches to the piece that opens and closes the flap to recirculate the inside air. You should be able to see it with your head on the driver side floor and a flashlight pointing up under the dash.

BS911

The vacuum does not connect to the CCU. It connects to a box under the dash up behind the CCU. You should see a clear, hard plastic hose under there attached to a 90 degree rubber elbow. If it is the culprit, you will actually see it NEXT to a rubber elbow.

I've never really looked into cleaning the drain, but you should see a rubber plug outlet sticking down under the car. Maybe a coat hanger wire run up it would free any junk if clogged.

In a properly charged system, idling, the compressor should not cycle on/off at all. It should come on and stay on. Another key note... you will get noticeably less cooling effect at idle. You really need to get up to 2000 rpms to get enough compression going on to get that refrigerant working. A couple other things that will alter your cooling capabilities...

The condensor fan. If it is HOT outside then you need that condensor to really effectively cool the refrigerant. If the fan in front of the left front fender is not running with the A/C on, then you will get noticeably less cooling in HOT weather. When you hit the a/c button, can you feel/hear that fan kick on?

Expansion Valve. You said you suddenly lost cooling. That sounds like a catastrophic internal refrigerant system failure. Either a complete loss of pressure due to a leak, or a stuck open or closed expansion valve. If you lost pressure due to a leak, your compressor would shut off. If the expansion valve isn't working, then the refrigerant will either not compress at all (stuck open) or it will get blocked pre-evaporator and not cool (stuck closed).

Here are a couple other questions...

I hate to ask a dumb question, but are you sure the compressor clutch kicks in and the outer half of the assembly on the belt is turning? I only ask because some have misinterpreted this. Please forgive me and skip ahead if so.

Second, after running a few minutes, preferrably at ~2000 rpms, do the lines headed in and out of the compressor change temperatures? One should be hot and the other cold? Short of having a dual pressure gauge (~$70 at auto parts store) this is the only way to tell if the refrigerant system is actually doing anything and will give us another step to take perhaps.

rbeggs

Thanks for your quick reply to my sort of sideline query. I'll stick my head on the floor as directed and I'm sure be dissapointed by what I see. This, when my hapless, 1 week old, C4S gets back from the shop where it is undergoing evaluation for what appears to be a hopelessly scrambled brain. Two shops have had had zero luck with reading DTS codes. The "Hammer" and something "even better" have come up with 41 unknown DTS codes. Lots of head scratching. I can't begin to describe how it tries to or doesn't run. I'll have more questions later when my membership kicks in and I don't feel like a moocher

'96 C4S_1 week
'62 356B- 30 years

geolab

Here is the diagnosis and repair proceedure for error 41

congrats on the new 4S and membership

click pdf. and save for reference

JasonAndreas

The drainage tubes are located behind the fuel pump cover opening. You don't need to remove the cover just look in the small opening denoted by the red arrow.




Is the DME control unit responding with 41 codes or the CCU? If its the DME control unit I would check for aftermarket performance software, specifically if someone soldered a replacement "performance chip" onto the main PCB or swapped out the unit for a MY97+ ECU with modified software. Aftermarket performance software has been known to cause problems with reading fault codes.

geolab

Is it 41 like 41 different codes? or error code 41? I'm lost.

rbeggs

The DME is what's coming up with the 41 different codes. Don't ask. I'll know more later

By "head on floor" I meant drivers side footwell floor, though the garage floor view of the AC drain hose location is a useful tip none the less. The next day or two should bring interesting news on the C4S's "brain" disorder. That first then the AC. The complexity of this vehicle is a quantum leap from my 356.

Thanks,

'96 C4S_1 week
'62 356B- 30 years

BS911

Man Richard! Sorry to hear of your rough start in 993 ownership. Don't worry about membership kicking in... we won't release the hounds on you too bad. Well... as long as you post some pics of your new ride to start us off.

993 Azul

Thanks Brian,i checked and the clear plastic hose is attached,One of the lines gets very hot but the other one does not get cold, and yes outer half of the compressor engages.
I mispoke when I said "suddenly",actually the air is barely colder with a/c on than off.The heater works and the sliders also work as designed,the compressor does not cycle and there is no condensation after turning off,the front fan works and i drove it for i hour on the freeway without
cooling.Sholud i take it for a recharge?Thanks

Joseph