ScottyP

Wrecked my 95 C280 and just acquired a 99 C280 as a replacement.

Lots of stuff is quite different. Found so-far changes/improvements to: engine, vacuum setup, and HVAC system.

Currently, I have 2 component questions:

1. HVAC. How do the HVAC module work on this car? I can only get the selector arrows for upper, lower and upper/lower.
I can NOT get the selector on center vents.
Is my unit broken? Does the middle vent produce warm air ever??

2. CAN system. Does this car have a CAN system? How can I tell if its installed?
Radio installed is a Becker 3309 (CAN compatible) and doesnt illuminate with the dash lights.
Contacted Becker and they say this is NOT OEM installed and will NOT illuminate due to lack of CAN in 99 model.
Becker instructs that car was manufactured with the BE-3302 unit.

Anyone knows is Becker is correct? Or do I just have a busted LED display?
BTW, the BE-3309 unit works otherwise and gives excellent sound for OEM.

MTI

As a rule, Mercedes vehicles do not have heated air through the center vents. Only chilled or outside fresh air.

ScottyP

On my 95 C280, it produced heat thru the middle vents.. Guess they dropped that feature later..

But, what about the side vents? I have not found a way to select the Side vents only.

ScottyP

Please help.. I know someone here can answer my questions?

vinceC

The center vents do not normally produce much heat in any W202 if the system is working as designed. Even though the earlier control panel has a button for dash vents exclusively, that is misleading because during the heating cycle the system is designed to direct that flow primarily to the outlets at the ends of the dash. There are certain conditions in which some heat will come out the center vents, but it can't truly be selected exclusively. What can be confusing is when the system is in a range between heating and cooling, warm air can sometimes flow through the center vents. Also, on an older car, the foam seals on the flaps deteriorate, so leakage occurs. From the OP description the control panel is working normally.

I can't be sure, but I don't think any W202 had a CAN bus. Perhaps the head unit was replaced with one from a W203, which does have a CAN bus. The units look identical. Maybe Becker will do a trade in?

ScottyP

Thanks for the info Vince. The radio appears to be swapped and Becker has agreed to sell me a trade-in (cheaper than repair cost).

Well after further investigation, I think my HVAC systems is in DEFAULT air delivery:
All settings deliver ventilation ONLY to the Defrost & side vents.
The HVAC selector does not display the center vent arrow ->; only Up & Down arrows.
No heat at the floor vents in all settings.

So, I have begun testing. Removed the glove box, unbolted/unplugged the vacuum vent control unit, and tested all lines using the Mityvac going to the vent pods. All vent pods are holding vacuum pressure. Followed the green vacuum line to the firewall and no breaks/cracks. Assuming all is fine inside of car, Im now inspecting the lines in the engine bay.

On the 95, the vacuum distribution block was up top by the ECU connectors & Overload Protection Relay. On this 99, none of this exists. Ive been unable to locate the vacuum distribution and dont know where the OPV relay is located (surely it will blow in the future). The green line disappears into the passenger side front wheel well. Tomorrow, Im planning to remove that wheel and wheel well cover, in search of the elusive Vacuum Distribution block... On the firewall, the green line is connected to some sort of valve. How do you test that valve?

Anyone knows exactly where the following items are located:
Multiport Vacuum Distribution Block?
OVP relay?

vinceC

There is no OVP relay on the later cars.

As far as I know the vacuum block was eliminated. I believe the green line goes to a vacuum reservoir in the upper wheel well. There should also be a gray line from the vacuum source. I don't know of a valve at the firewall - could it be a vacuum connector?

I have to think your problem is with the HVAC Control Module (N22). As I understand it, if you press the air distribution button repeatedly, the arrow indicators stay the same, up and down.

I also have to correct myself. In my research I found that as of the '97 Model Year there is a limited CAN bus. It looks like it is limited to the Instrument Cluster (A1) , HVAC Control Panel (N22), Engine Control Modules (N3/7, N3/10, N3/11, N3/12) and Traction Module (N47). I cannot find any connection to the Audio 30 system.

These cars changed every year throughout the model run. The changes were extensive and it takes good forensics to figure out what you are dealing with.

ScottyP

No OVP... Kewl.. I hated that thing in my 95!

The HVAC Control Module is the digital display type and uses the radio keys to remove it.
Does it need to be reset somehow?
Are you saying that I should repeatedly press the air distribution button to reset it?

I will look for links for Control Panel help...

vinceC

The HVAC Control Module (N22) is the unit with the display that comes out with the radio keys.

[QUOTE]Are you saying that I should repeatedly press the air distribution button to reset it?/QUOTE]

It does not reset it. Repeatedly pressing the button scrolls through the selections available. From AUTO, one press = arrows up/down. Second press = arrow down. Third press = arrows down/center. Fourth press = arrow up.

During this drill you should hear the flaps shifting.

ScottyP

Okay. Thats why Im thinking my system is stuck in default mode.

From AUTO, one press = up/down, second=up, third = up/down, fourth = up.
Dont get down alone & dont get down/center. No shifting flaps.

Floor vents do not open. Air Circulation from Defrost & Side vents with all settings.

xvvvz

Just for another data point, my 99 has always had heat come out of the center vents since new. Many other people in other forums have described that their car has had center vent heat too because they notice it when it stops from a messed up vacuum system.

There also is a CAN bus system in this car but I don't know the extent, if any, is related to the stereo. The rear window controller is notorious for going out on this car and causing all kinds of problems in the system that seems unrelated (e.g. a rear window controller goes bad and the front windows malfunction).

xvvvz

Scotty, if you have the digital display controls for the air conditioning, have you run the diagnostics via the digital display to see what codes it throws out? I don't have the procedure but it has been discussed in the various w202 forums on the net and a little searching should allow you to find it easily.

ScottyP

xvvvz, Thanks for the tips.. I just found the procedure for pulling dignostics for this car last night. My old procedure only worked on the push-button type HVAC control. I will be pulling codes today. I am also pulling the front passenger wheel to inspect the vacuum lines & connections.

Maybe after getting this thing working properly, I will get center heat too ! !
But, I would just be happy with footwell heat working currently.

What is the Rear Window Controller called? How do you test if it is bad?

vinceC

xvvvz has a good point about the DTC's. The attachment W202 HVAC DTC has the procedure - scroll to page 4.

There is also a procedure for getting real time values from the system. See the second attachment. There is a difference for the W202 however. To get the values on a W202 perform the following: Key in Position 2, press "Rest" button for 5 seconds or more, scroll through the values using the fan speed button. Press "Rest" again to exit.

I must clear up this issue of the center vents though. The following is directly from the WIS (Workshop Information System - the factory subscription site):

* Heating mode - heated air flows from footwell and the side air outlets, as well as bleed air from the defroster outlet.

* Cooling mode - cool air flows from center and side air outlets.

* Mode change - footwell, center and defroster air outlets can be open at the same time.

As I said before, you cannot "select" the center vents. Most of the time air will only flow from the side outlets, but there are times when the system is shifting between modes, something it does regularly, you might experience heated air coming from the enter outlets.

xvvvz

>>As I said before, you cannot "select" the center vents.<<

I will agree with you here in that you cannot specifically select the center vents only (unless of course you manually turn each outside vent off) but when you turn on the heat and have the selection to distribute heat through the front (face for lack of a better word) vents, heat does come out of the center vents. Maybe this is something they changed when they went to the "facelift"/post 97 models or something (because I know what you say is true for older MBs), but it definitely pours out the heat just like the side vents.

vinceC

I just realized that there is a link in Steve's article to a very handy chart (Chart 2) that doesn't work in a .pdf. The article is in a post by Steve on the thread below from mercedesshop. In fact, if you do a search on mercedesshop for posts by Stevebfl you will find a ton of valuable info.

http://www.mercedesshop.com/shopforu...ad.php?t=40964

xvvvz - I researched that when I checked the WIS - what I posted is valid for pre and post facelift. FYI, I have both - a '95 C280 and a '00 C280. They behave as M-B says they do - as does my W210 by the way. I have never had heat "pour" out of the center vents.

As I stated earlier, the foam seal on the flaps for the center vents deteriorate. Once that happens, they can leak a fair amount of air. I renewed the foam on our '95 about two years ago when I had the dash out. It was pretty shot.

Let us know how you make out Scotty.

ScottyP

I did not have any time today to do anything. Out-of-town family and friends arrived earlier than planned today for the Obama celebrations here in Washington, DC next week. Ive been cooking & entertaining all day. Maybe I'll get a chance tomorrow. I will post my results.

>>As I said before, you cannot "select" the center vents.<<
The middle vent arrow never shows up on my display. Its like I dont have dash vents at all.

Thanks Vince for the attachments. I have talked to Stevebfl on a few occassions in the past when I had problems with my 95 C280. He is very, very knowledgeable and helpful. Great guy. BTW Vince, I had hordes of heat coming from my center vents on my 95 C280. It had the push-button HVAC control unit and cranked heat from both center & side vents. I had to remove the dash & replace all of the pods about 2 years ago (no air - hot or cold - from center vents). After that, I got heat from all the vents (defroster, center, side, floor & rear floor) gave excellent heat & AC. Thats why I miss it in the 99 C280. I too had to replace the dumb crumbling center duct foam seal rings. LOL. That surely was a bad MB design flaw...

What is Facelift/Post 97 models? What was facelifted?
Didnt MB change the Body style & interior for the C-Class in 2000?

xxvvvz - What is the Rear Window Controller called? How do you test if it is bad?

I also need someone to show me how to use the new Browser based WIS program... Wheres the diagnosic/repair stuff located??

xvvvz

Hey, to each his own but I just want others to know they do have a choice (at least with a '99) and it is really nice in this cold weather to get lots of heat coming out. I know that I have had heat coming out of the center vent since this car has been new, so that negates age related issues in my case. I just checked my manual and it refers to setting both the center vents and the side vents when setting the heat function. Heat is basically equal too, so know it isn't leaking or residual heat.

I did find a diagnosis document in WIS that helps troubleshoot heater function problems. It notes that when you get "side outlets, heated air" + "center outlet, no heated air" that the "possible/cause remedy" is/are "23 -> 3.0, 4.0, 5.0" but I am not sure what those mean. I would have to dig into WIS more to find that out.

xvvvz

Facelift is when they update the bodywork slightly. You can see the difference in this thread at benzworld (if they will let the us post threads for another forum here). Post #2 of Doin12volt is pre-facelift. Post #4 by "'91 300CE" is a "facelifted" model.

http://www.benzworld.org/forums/w202...es-sticky.html

ScottyP

K... I have a FACELIFTED 99..

So, Im not the only one having problems finding stuff in the WIS.. You would think that it would only show items that was associated with the VIN # entered. I also expected to find decent diagnosis steps with possible solutions by component. But, Ive only been using it for 1 week.. The EPC component is Great ! ! and has what you would expect to find ! !

xvvvz

Yeah, it is pretty much 1980 technology! I have the 2005 version. Apparently, the versions within the last year or so are more Windows friendly but I have been afraid to upgrade just because it might barf on any components left over. I haven't tried to install it on a Vista machine yet. Have you?

xvvvz

You have found out about the REST function, right? Very nice during this cold weather!

ScottyP

Kinda..
I know that it will give heat with the car off if you activate the REST function.
Does it help while driving?

I installed in on a XP system. I too thought it would barf on Vista/Win7..

xvvvz

I believe it only works/can only be activated when the engine is off. There is a good discussion in the manual on how to do this. You basically press the rest button and the fan will come on low plus there is a small auxiliary water pump that will continue to pump water through the heater core and thus continue to heat the car for up to 30 minutes (there is a low battery automatic cutoff if the battery gets too low). Make sure to dial up the heat setting to the hottest setting while REST is running.

I was reading the manual last night and it said REST can also be used when it is hot outside to circulate fresh air in the cabin by turning setting the temp to the most cool setting (no air-co compressor will be running though). I had never really thought about that and wonder how effective it would be. It would probably be good to crack a window if possible or leave the back of the sunroof in the vent position.

ScottyP

okay.
Finally did the test today. Here's the results:

DTC test
Continuous Fault
42 1
Intermittent Fault
41 6
41 7
41 9
End

Real Time Values
01 74F . . 40 03
02 44F . . 41 03
03 116 . . 42 03
05 101 . . 43 6-C
06 204 . . 50 114
07 05 6. . 51 80F
08 102 . . 52 32F
09 50F . . 54 OFF
10 335 . . 60 OPE
20 00 . . . 61 0.9
21 060 . . 62 0.9
22 000 . . 63 0.9
23 000 . . 64 0.9
24 14.0 . .65 0.9
. . . . . . . 66 0.9

Now. I will need to figure out whats good & whats not...
What are these DTC codes? They are not in the list ! !