Greetings and on to the next problem with my new to me r230.

I cannot get the heating system to work. I have read the Owner's Manual and tried all sorts of ways to both manually and automatically set the cabin temperature. Nothing even slightly warm comes out of any of the vents. I have even tried the residual heating unit/motor engagement.

The hose from the block to the auxiliary pump is hot as well as the hose going out the auxiliary pump towards the firewall. I can hear the motor running. This is a new aux pump. Is there another control/servo/valve that is supposed to open to direct warm/hot water to the heater coil? I did replace the radiator and properly fill the radiator/coolant overflow tank with the proper concentration of the approved blue coolant. The only thing that may be of interest is that there is currently no refrigerant in the A/C system because it had to be evacuated to change out the radiator and condenser.

I hope this is something obvious that I am missing.

Any comments, help, or descriptions of similar problems with be appreciated.

Robert

 

While it could be an electrical problem, it could also be a stuck heater valve which is behind the firewall. Obviously you first want to eliminate electrical problems such as a blown fuse.
Once you eliminate everything else, you have to consider the heater valve.
If you look for this problem on YouTube, you will find several vids about accessing the heater valve by British guys who remove the entire wiper assembly. Fortunately for left hand drive cars, there is a likely simpler way where the windshield cowl and wiper assembly/motor do not have to be removed. Instead you pop out the pseudo-firewall plate behind the engine by removing 4 bolts.
Personally I have removed the cowl and entire wiper assembly for a different reason and it is a pain. At that time I did not know about removing the pseudo-firewall plate. So, I haven't done that yet personally, but it appears you only have to remove its 4 bolts, 2 on each side, pop off the hood weather-stripping and yank the plate up and out. You then have access to the heater hoses, the heater valve, the A/C lines, wiper motor and such.

Hopefully others here have simpler solutions.

EDIT: I no longer think that removing this firewall plate is a possible way to access the heater valve. At least not simply. See my post below.

 

Yes, I started to do some research and it seems the heater control valve is often culprit. This car came out of South Florida so the valve probably did not get "worked" that much. I got the bulletin on removing this valve and it directs you to take out all of the wiper system. So the possibility I wont have to do that is great.

Can you give any direction of just where and from what angle to approach those four bolts?

Thanks

 

If it's the valve, and once you get it fixed, if it doesn't hold temperature properly then you likely have a broken thermistor in the overhead control panel. They fall off.

https://www.benzworld.org/threads/in...#post-18144033

One of the lowest cost fixes you can do on an SL!

 

You may not have the system bled fully either. Sometimes they are hard to get the air out of

 

I might be completely wrong in claiming that you can remove the pseudo-firewall plate to access the heater valve. I read comments that you could, but never saw details.

Anyway, here is one of the 4 bolts. Another is about 8" directly below it. And then mirrored on the other side. HOWEVER, I forgot some details which complicate this...
First, there are two bolts in the rear of this plate which hold the wiper assembly in place. Might be easy to remove, but might then be difficult to replace if the assembly moves; might have to at least remove the lower windshield cowl.
In the following pic with the engine removed, I see two more possible bolts on the left side, highlighted in yellow. Some of the spots which look like bolts are actually just push-pins to hold the felt lining in place, but others might be bolts.
Also, on my SL600, the engine harness went through this plate; no idea if your SL500 is that way too.

At this point I'm think you would need to remove the windshield cowl to see where everything is. I think there will be enough working room on the right side that the wiper assembly will not be in the way.


The two possible bolts, in yellow circle, give me pause that removing this plate would work for you. It might even hold the heater valve. (Ignore the red arrows, that was for something else.)

 

Here is a follow up for everyone.

I confirmed that the 2 heater hoses to the heater radiator were not getting hot when the heater valve was activated. I replaced the heater valve/motor. A few comments regarding that. I did have to dis-assemble all the components in the battery area, The battery tray, remove the wipers (both sides) and the plastic covering. There may be some short cuts but I felt it best to remove these thing to prevent any damage and to better access the valve. The valve has four heater hoses attached and all are attached using spring clamps. Those are very difficult to get to. Three of the four nipples just broke off in the process. This actually made it easier to get the clamps off. They broke because they were brittle from age - probably the original valve to the car. Care was attended to insure that no broken pieces fell into the heater hoses.

I replaced the valve/motor with regular worm/jubilee claps in stainless steel. This was much easier and will make easier service should this problem arrive in the future. Upon running the car the and setting the system to max heat all four of the hoses got equally hot.

So here is the problem: This did not effect the heat in the car thru any vents/outlets at all. I connected to my iCarsoft MB II Version 11.80. In the AC menu I found all sorts of codes relating to the faulty communication with the baffle system. That list follow at the end of this post.

I used the copy of the fuse/relay diagram that someone posted that came in their trunk near their spare tire. I could find no relay or fuse that corresponded to the air diverting/baffle system. I have checked all fuse/relay box locations and there is no sign of previous water contamination.

So suggestions anyone?

Thanks



From iCarsoft:

Communication error of AC bus with component B 31/1

M 16/27 space diverter flap actuator motor communication fault

M 16/21 fresh air and recirculated air flap actuator motor communication fault

M 16/13 left defrost nozzle flap actuator motor communication fault

M 16/14 right to force nozzle flat actuator motor communication fault

M 16/15 left foot well flap actuator motor communication fault

M 16/16 right foot well flap actuator motor communication fault

M 16/23 air flap actuator motor left center vent communication fault

M 16/24 air flap actuator motor, right center vent communication fault

M 16/28 left blending air flat position motor communication fault

M 16/29 right bleeding air flap position, motor communication fault

M 16/25 air flap actuator motor, left side vent communication fault M 16/26 air flap, actuator motor, right side vent communication fault

 

Is the Component B 31/1 the entire control unit assembly for the climate control?

 

@HLG600 @mrvedit @Tom Manning Et. al.,

Would you please comment on my entries #7 and #8 on this thread? I was considering a starting point of just removing the unit and checking/cleaning the contacts in the pin multi-connectors.

Thanks

P.S. I am not sure if I did the tagging correctly above so as each of those three members will get a notification. Any comments or help from anyone in that area will be appreciated. Thanks again.

 

Component B31/1 is the multifunction air quality/temp/humidity/etc. sensor. I had accidentally not reconnected the connector when I re-installed the air duct box. I removed the air duct box when I was replacing the heater valve.

So that removes the first fault on my list above but all of the other faults regarding the flaps still persist.

 

I think next step is to figure out where the connector is for the communication related to the M16 codes. Either disconnected or the CAN bus wires are corroded to broken.

 

Thanks for your response and suggestion. Being very new to r230s can you give me an idea where the connection to the CAN bus is? Also, is there a logical place where the wires would be corroded or broken? Thanks a lot.

P.S. I enjoyed the conversation the other day.

 

I just fought this same battle with mine. I replaced both pumps and finally bought a STAR system to scan it after the new pumps did not fix the no heat issue. Turns out the AC control unit had a small black plug unplugged from the back of it, probably due to a PO's stereo install at one time. This black plug controls all vent opening and closing and plugging it back into the control unit and fixed all my heating issues. If you pull the center console and look at the back of the climate control unit you'll see the missing black plug. It should be floating around somewhere in the vicinity, I saw my wire lying there even before I had the center console fully pulled out.

 

Thank you for this comment. This is actually what it was. I believe you or someone else made the same post on a different thread or Mercedes forum. That’s how I learned about it and fixed it. Regardless, so many thanks because this was the actual problem. By the way, that little clip that has a black head does not have one of those connectors that holds it in place like most connectors do. You just kind of push it in and it only has friction to hold it in place.

 

Glad you got it working! I tried to post pics of the plug and scan codes, but it stops at 90% when I try to upload. I'll keep tryng so if anyone has the same issue they can reference this thread.

 

Thanks for trying to upload those pictures. I went back and found a couple of examples so people following along now or in the future can visualize where the plug goes. The first picture shows the general temperature control unit from the front. The second picture shows where the little small black plug is inserted. This little male plug is black, has a unique shape, and only has about three or four wires. It is very easy to miss when reinstalling the unit. Also, as I noted previously, there doesn’t seem to be the little pitch clips that hold it in place. There must be some rather small detent but you can easily pull that plug out without much effort at all. I suspect this happens a lot.

So I offer this as a warning to all. When you reconnect this device make sure that one of the last things you do when reinstalling the center console is to check to make sure that that plug is in place.

 

I had to create a new account to upload the pics. Here is the STAR scan results in case anyone needs a reference on what to look for.