May not be the A/C

On my 2000, the A/C blows hot air. It appears to blow hot, somewhat dry air since it can defrost in a pinch, although not very fast.

This suggests to me that the condenser and compressor work, but the freon (is it freon?) is low?

Any general advice?

Anyone know where to check the level?

Any advice on topping up?

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

The heat control may be the culprit. The heat and A/C work together to defrost. That's all I know, so not much help. I just wouldn't assume A/C if defrost works.

This is not limited to def setting . I simply used that as a clear diagnostic as to whether the air was being de-humidified, and thus as a proxy for the operation of the compressor.
The A/C is most definitely not working.

I'm suspicious its as wimple as the system was not refilled when the motor went back in.

Good idea though!

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

and the temp must fall within the ranges given for ambient air temp in a certain amount of time.

If the temp doesn't fall into within the ranges given the system must be checked for leaks and repaired.

This involves pulling a vacuum on the system for some vehicles 1/2 hour others 1 hour and verifying the low pressure remains within an acceptable range.

If it doesn't refrigerant (R134a IIRC) is added to the system along with a dye and the leaks found. The system is evacuated, opened up and repaired.

Then the system is retested for leaks.

The refrigerant is collected, washed, and used to flush the system of any contamination (water or ?) and then oil. The oil is collected and the proper amount of oil is added to the system then the system is filled with refrigerant. (The amount of oil that is required to be added for each component that is replaced is also given.)

The amount of refrigerant is 900 grams (though the amount is tied to the VIN so this must be verified) along with 195 +/- 15 cm^3 of ND8 oil. (Again the amount of oil even its type much be verified using the VIN.)

The system is charged then tested to ensure it performs to specification.

If something mechanical/electrical is suspected the PST2 (PIWIS2 now I guess) is connected and the A/C test drive link selected and the diagnostics computer checks out the A/C/heater control operation, electrics, etc.

The dealers have special A/C equipment that automates a lot of the above to take the guess work out of how much refrigerant to add and how much oil was removed and thus needs to be added, and so on.

which you should be able to tell by condensed water dripping from the bottom of the car when the A/C is on.

If the A/C is working then the problem is that you're getting A/C + heat, which is a totally different problem than the A/C not working.

I believe my test indicates that:

1. the air is being at least somewhat dried
2. the compressor clutch is engaging and the compressor turning

I have nto run it sufficiently to check for water draining.

Will do. Thanks to both of you

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Quote
grant
I believe my test indicates that:

1. the air is being at least somewhat dried
2. the compressor clutch is engaging and the compressor turning

I have nto run it sufficiently to check for water draining.

Will do. Thanks to both of you

Grant

to result in a significant amount of water to condense on the evaporator and drip down. The water drain may be plugged.

Why not check the A/C is functioning by the most straightforward method? Turn it on, adjust the settings as called out in the factory section on troubleshooting the A/C and see if you get cool air that falls within the ranges given for the ambient temperature at the time of the test?

The water dripping was suggested by two others so i was acknowledging that i did not yet do so.

The culprit could be many places however:

- low charge of r134
- non-functioning compressor (testing to see it that is working, and it seems, "yes"
- blend valve/door not working

That's what i'm trying to narrow down at the moment. Then fix.

I'll re-iterate that i have listened for clutch engagement (yes); motor bog (very slight) and tested to see if some dehumidification occurs (yes).

So i think i'm down to the blend door or freon. Since the motor came out, i'm thinking freon. Darn, leaks are a PITA.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com



Edited 2 time(s). Last edit at 05/24/2013 03:55PM by grant. (view changes)

be a problem but moisture could be in the system as well. This can freeze and block the flow of refrigerant and all the refrigerant in the world won't make the thing blow cold air.

If the refrigerant isn't flowing while the compressor is running the compressor can run with insufficient oil. There could be insufficient oil anyhow if the A/C system was opened up. Lack of oiling can ruin a compressor.

If you fail to address all the possible issues and in the right order you could turn a rather inexpensive to address problem into an expensive to address problem.

Before I did much messing around I'd have the A/C system properly evacuated, checked for leaks, the oil flushed and the proper amount of oil added, then the proper amount of refrigerant.

Then you can trouble shoot an air flow problem.

Might add for a test I turned on my Boxster's AC today leaving the restaurant. In just a few hundred feet of driving in 1st gear through a parking lot the A/C was blowing cold air. I had the controls set at 72Fand in auto mode. When I pushed the auto button to turn on the A/C almost instantly I could feel the engine react to the increase in parasitic load from the compressor and the alternator as it now had to supply power to the cabin vent fan and the radiator fans.

At work after letting the car sit a few minutes I checked under the car. No water from the evaporator.

There's always enough humidity.

Diagnostically it's almost always best to start with the trivial tests that yield relevant information.

In this case, if he sees the dripping it's good information. If he doesn't, he hasn't learned much. Either way it takes only a minute to check.

I had to wait for our cold spell to snap before i could begin some simple tests (philosophically agreeing with Boxsterra's approach of trying the simple things to isolate areas first).

1. With the ambient temp at around 70-73 degrees, and the motor cold, i turned on the A/C. Air was blowing at ~ 90 degrees, falling to around 86 degrees presumably as warm ducting cooled. This leads me to believe that a) the A/C is not cooling the air and b) it is not the heater mixing in warm air.

2. I left it running for 6 minutes in humid weather to look for drips. The complication is that it rained last night and lots of stuff potentially could drip. I did se a small amount of water coming from the center, front, just behind the front wheels (but in the center of th car). Is this the place for the A/C drain? Or did i just see water coming out of the bodywork?

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

The A/C will drip from under the center towards the front of the car and there is nothing else up there that would reasonably drip.

So that indicates that the A/C system is functioning which means that the problem is either inadequate cooling (low gas pressure and/or moisture in the system) or that the heater is operating errantly. From your original problem description it sounded like the air was being heated (not just not cooled).

While it is possible to measure the pressure of the cooling system gas and to inject dye to check for leaks I would again go for the easier diagnostic route and target the heater. That is unless you already have an A/C pressure gauge.

You can pull fuse D6 ("heater relay") and see if the problem goes away. That would tell you if the heater is the problem.

Does the car blow above-ambient temperature air when you put the temp on "low" and the fan on "hi"? That would indicate that the heater flap is sticking.

and control over several of the functions. If you can get your hands on one that would be helpful.

... that in it i basically ruled out the heater mixing, since it blew warm air, with the unit on low, while the motor was stone cold......

I'm almost 100% certain its low on r134a. Unfortunately, that just means the fun begins, tracking the leak.

I may have a lucky (or not) break - the guy who put the new used motor in said he had issues with one gasket/connector and plans to show me which one. That would explain everything.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

After carefully rereading your update post since you said the temp went down I agree that indicates it's not coming form the heating system.

In my experience, the easiest way to find leaks is to use a dye. You inject the dye into the system, run the A/C, then turn on a black light and the leaks glow.

The second easiest way is to use a leak detector, something like this: [www.amazon.com]. You wave the detector along the different parts of the system until it makes a sound and then you've found it.

I went to my local, friendly porsche race shop and friend.

I also bought a gauge and a can of r134a with the dye in it for diagnostics.

We evacuated, and filled her up (mostly, to the green zone). So far its holding pressure, and we saw no obvious leaks form the points we suspected. I guess that's good....

\My plan is to see how long it holds a charge, and, when i can, look around with a black light.

Immediately blew nice, cold air.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

You can buy a gauge at a parts store and us it to test the pressure on the low pressure side of the system. They are cheap. The parts store gave me one that a customer returned. When testing just keep the valve closed if you don't have a can a refrigerant attached to the other end. If you find the pressure is low, then buy a can of refrigerant that contains dye and refill the system. Don't buy a can that also promises to stop leaks because it will mess things up at this stage. Once you charge up the system, you should see low temp air coming out of the vents once again assuming the compressor is working. If it does blow cool air, continue to run the AC until it stops blowing cold air. This map happen in days, weeks, or months. Then use a UV light to look for dye. The hardest place to find the dye is when the leak in the evaporator inside the sealed heating box under the dash. One trick is to pull the drain hose up through the hold in the passenger foot well. Just follow the tube down under the carpet and you see what I mean. Then look for dye inside the drain tube.

We never ever ran the AC in the Winter periodically as per the manual during the 12 years of ownership.
Didn't even know that was something we had to do :-)

Anyway, the AC in our 2000 Boxster started acting up last Spring so we topped off the refrigerant:
FirstLook:
[www.rainydaymagazine.com]

FirstUse:
[www.rainydaymagazine.com]

At first, we didn't think it worked, but it turned out that we didn't add enough for the compressor to kick in.
Once we got enough into the system, the air was cool again.

This Spring, we had to added 24oz before the AC would cool.
Clearly there is a leak somewhere, but it is very slow.

Also, at $7 for a 12oz can...we figure the $14 fix is cheaper than actually figuring out the root cause.



Edited 1 time(s). Last edit at 05/23/2013 10:34PM by RainyDayGarage. (view changes)

Grant

gee-lenahan-at-gee-mail-dot-com

I just went thru the same problem with my Honda. it blew hot air. Turned out condenser is leaking. Put some dye in at the same time you refill with refrigerant (make sure, no leak sealer please) And buy an ultra violate flash light. It will show you if you have a leak or not.

Thanks,
Tony

... in the way they manage HVAC.
The Porsche's heater is always on. There's no bypass valve, so coolant always runs through the heater core.
The way Porsche controls it is with air dams. They block the air coming off the heat core when all you want is cold.
In some cases, the AC may be working but will be offset because of a bad air dam allowing heated air to come through.
A way to test this is by running the AC when the engine is completely cold. At that time the coolant will not circulate because the thermostat will shut it off until it reaches operating temp of +/- 185F.
But, having said all that you may just have a small leak and your 134A level may be a bit low.
You can purchase a pressure valve which connects to the low pressure side of the AC and that will show you the correct pressure charge.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna




Edited 1 time(s). Last edit at 05/24/2013 09:09PM by Pedro (Weston, FL). (view changes)

I plan to run this test. Unfortunately he also said " i think we had trouble with a fitting when we hoisted the motor in"

Which means it may very well be a leak.

Thanks again to all,

I'll post the eventual problem and solution.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

i'll have to try another day.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

If you try Pedro's suggestion, you should feel 60 degree air coming from the vents when the AC is on. You can test this pretty closely using a kitchen meat thermometer. If the system isn't blowing cold air, then mostly likely you have a leak. You can pay a shop to do a vacuum test. If it holds, ask the AC shop to put dye in the system when it refills with refrigerant. I had a good vacuum test, but there was still a leak on the high pressure side of the system that wasn't apparent until the system was under pressure as opposed to vacuum. It turned out in my case that the leak with in the evaporator under the dash. I found this out by pulling the drain hose up on the passenger side and saw it was lined with dye when I shined a UV light on the end of the tube. Good luck.

Most systems specify around 45 degrees.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

IIRC, I got the 60 degree number from the AC shop where I took my car for diagnosis. I have a small leak in my evaporator. When I top off the refrigerant, 60 degrees is also the number I get when testing myself. Perhaps someone has a better number.

gives the desired cold air temp from the center vents for a range of ambient air temps.

There are some prerequisites before measuring the air temp. From memory the ambient temp can't be too low (s/b above 3C IIRC), all doors, windows, the top, the sunroof should be closed. The A/C fan speed control set to high. The air temp set to min. The engine started and run for a few minutes before the test. At the time the temperature is being measured the engine rpms raised to IIRC 1500.

A temp probe inserted several inches into the center vent is then used to measure the A/C air temperature.

While I can't tell you the temperature reading exactly I can assure you it is way lower than 60F. I've run this test at least once and the air temperature after a few minutes was down to under 40F. I do not recall the ambient air temperature but I'm pretty sure I did the test if not on a hot day at least on a mild to warm day and certainly not a cold day.

Marc is correct. I looked up the paperwork and it was 40 degrees outlet temperature from the vents.

Grant

gee-lenahan-at-gee-mail-dot-com

sensor "guns" available as well as probes that measure the temp. I found the gun interesting to own as it enables things like seeing the temp of your home's floor versus ceiling, air register temps, temp on inside and outside of tire tread, etc. Have used it to see the temp on a car's A/C too. IIRC, about $30 via the net. Battery powered and point the laser and the dot shows what it is measuring.

Grant

gee-lenahan-at-gee-mail-dot-com