Alright, starting A/C minor overhaul...

[Sulaco]

Alright folks. Here comes another heavily documented DIY on a w202 (like the head gasket job...). Once again on my pre-update m104 1994 C280. She's my tank. No matter how much grief she gives me, I can't live without her...

Alright, so I had a previous thread that sort of scratched the surface as to what's going on here. But here's a basic run down again:

For years the center vents have been out. Common problem on a w202, I know. But I'm going for gold on this round... Also, the front defrost/defog vents and side dash vents ALWAYS RUN. ALWAYS. In winter when I try to manually set it to floor vents only, all it does is ADD floor vents to the formula. Odd.

For about a year now, when using A/C system, the entire system looses power when using the throttle. At idle or at cruise, it's fine. Even when the cruise control nudges me up a hill, I lose roughly 90% of the power from the A/C fan motor. I'm told this is a vacuum problem.

And the straw that broke the camel's back is the fact that now I get nothing but room-temp air! No more cold air at all! Unless it's cold outside...

I pulled out my Blackjack to use as a camera (apologies...), and cracked her open a tiny bit to begin on this lovely, mild Sunday in the southeast. It's 85, breezey, and sunny. Perfect day to hate my car.

Here are some pics:

Removed panel under passenger side footwell. Here is mystery item number 1 that APPEARS to be misbehaving... I disconnected power to blowermotor to eliminate the impossible noise it makes. With engine running I turned on AC to LO. I can hear mysterious clicks and a hissing from this box. The hissing coincides with the repetitive running of the vacuum pump in the trunk area. There are about 6 vacuum lines on the back side of this unseen in the picture.
http://i283.photobucket.com/albums/kk290/kbc2b/PIC-0064.jpg

This spot also appeared to be behaving oddly. The crappy MS paint boxes will indicate... The vacuum line on top left pulls suction. The green line on bottom right appears to do NOTHING. Even with the top-left line still attached, I can feel no suction coming from the assembly when I disconnect the green-right line.
http://i283.photobucket.com/albums/kk290/kbc2b/PIC-0071.jpg

Here's the AC compressor. I've been told it needs a freon charge to restore cold air to the system, but I've also been told that if it's got freon, you can see liquid in the tiny octagonal window on top when you turn on the AC system, and I could see liquid indeed...
http://i283.photobucket.com/albums/kk290/kbc2b/PIC-0066.jpg

Any help is greatly appreciated guys. You've never let me down in the past.

[xvvvz]

I think you may have two separate issues - air ducting and then the issue with air cooling.

If this hissing is indeed coming from that box that you have already accessed and that is the only place it is leaking, you are lucky because you may be able to fix the air direction/ducting problem without having to completely take the dash apart.

Do some searching on air conditioning and vacuum. You will find links to a great tutorial by a guy who had to take the whole dash and vacuum system apart. Lots of pictures. I think it is about a 14 mb download.

[Sulaco]

Thanks for the tip. I was actually able to dig up the 15mb zip of Zade's guide. I was also able to get in touch with Zade himself, who has graciously offered his help, should I hit any snags.

Another point of interest is some of the things I've discovered while inspecting this whole thing.

WHERE THE HELL IS THE OTHER FREON CHARGE POINT. I've found one underneath the intake--black plastic cap included. I can't find the other one! Any tips as to where it might be? I REALLY need to recharge my freon, most certainly within the next 36 hours. Nothing would be more embarassing than the date I have lined up this weekend in my old benz with no A/C....

Also, while looking for the other recharge point, I found a hose stemming from the back of the water pump that connects to the engine just below the intake assembly. It was broken clean off right where it connects to the engine.

Oddest part? It doesn't leak a drop of coolant... And it appears to have been broken a while.

[Sulaco]

I've had the afternoon off today and I've spent it trying to do a
freon charge on the system. It's my first time so I was really
cautious and have taken my time. I started engine, engaged A/C, turned
temp to low, and used a 19oz can of freon with included cable/gauge.

Before I engaged can, I used the gauge to see what the pressure was.
It was down in the green "low" area on the can's gauge. I engage the
can but the pressure immediately jumped up into the red DANGER area on
the can. I turned valve back off to avoid an overfill. ACC was hardly
cooling at all. It was a tiny bit cooler than outside air temp (a
smoldering 95 today). I make a quick call for help (my brother) who
said to keep letting it jump into the red in small intervals and the
pressure will slowly fall down. I did so, and it appeared to help.
Eventually I could hear things start to work a little harder. The
clutch was already engaging before today, near as I could tell (at
least, when I would turn on A/C system the engine would have a draw
and work a little harder, RPMS would drop, etc).
But after a few minutes of on/off with the can of freon, eventually it
appeared the engine was starting to work a little harder. Eventually,
the AUX fans came on (good sign, right? they RARELY came on until
today). I kept going and going. Now the low-side pressure reads about
70PSI on the can's gauge and I'm afraid to try any further. Afterall,
it's on the brink of the red "DANGER" area of the can's gauge, but
that was the point at which I could notice an enormous difference. It
appears the A/C is coming back to life. It's much more cooler, but
still not quite as ice cold as it used to be. I ran some of the
diagnostics through the REST button and it gave me some very funny
readings. The 07 bank that's supposed to indicate refrigerant pressure
dances between 17 and 19 bar. I hear this is DANGEROUSLY high, but
I've also read that the built-in AC diags are complete bull on this.
But the AC is working FAR better now, so what should I do?

I've used more than half of the 19oz can. The gauge indicates it's
almost too high, onboard diags say it's almost 3-4 times what it
should be, but now it's starting to work...

Also, the 05 bank which reads acc evaporator temp sensor says 63
degrees. I've read it should read in the 30-40 degree range for normal
operation.

Also, the engine temp is MUCH higher than normal now. All spring/summer it's hovered around 80C when driving around city traffic (no ac, windows down). Now, with AC sort-of working, it hovers up in the 100C range and beyond. Something to do with that broken hose coming from the water pump that mysteriously leaks no liquid?

[Sulaco]

So chalk THIS one up to another year later...

Funny how, in the winter, I forget my car's problems.

I'm stumped, guys.

As per the posts above, I put a whole can of freon in. The A/C became cold again. For the next 2 weeks it slowly warmed up again to the point in which it was blowing hot air again.

I'm inclined to believe I simply have a leak somewhere, but I know this car's terrible history of tricking me.

Does ANYONE have any pointers or clues as to where I should begin or how I should proceed?

I was thinking the old trick of the black-light/colored freon and doing another recharge to trace down where the leak is. But something tells me that might be a bit dangerous. What if there IS no leak and overfilling blows something (like my compressor--if it's not already dead).

I don't even know where to START. I haven't had functioning A/C in half a decade. I've got other issues such as vacuum leaks causing vent issues or air-speed issues when I accelerate. But those are unrelated and I know how to track those down. I just want to make sure I've got a functioning refridgerating system before I go through all the trouble of removing my dash to replace vacuum elements.

Bill? Nenad? Thoughts?