mleskovar

Is the RichW still here? Question: I assume you go into recirc when the car is first started and you want heat. When the air goes to cold does the recirc light go out? Or I noticed the weather has warmed a bit your way and has the symptom gone away?

Glyn M Ruck

Thanks acr2001 - All you need to do with a partially blinded radiator is get stuck in the snow with no real airflow through the radiator - make the engine work really hard trying to get unstuck & you will likely overheat with only the fan operating. I think RichW has taken to the popcorn & a stiff drink

Rev 2 Liv

Didn't "TVT Design" Conclude that the stock thermostat on the M112 opens at too high a temp for performance reasons?

I'm planning on a new thermostat and aux. water pump for my heating issues, but wouldn't mind getting a thermostat that increased performance and decreased heat soak in the summer.

RichW

Hey guys,
Thanks for all the replies and ideas, sorry bout the delay in my response I was in Las Vegas on Vacation . I'm still suffering the issue, and just to recap:

- Brand new radiator
- Brand new thermostat
- Car never over heats, just temperature oscillates more than I used to recall it did
- Heat is very inconsistent at this point even with the new thermostat

Couple new things I've noticed, the only way I seem to be able to get it to go warm/hot is:
#1. Put the heater on "recirculation/Tunnel" mode (not super hot but decently warm)
#2. Drive car for 30 minutes or longer then heat seems to work normally, rock solid 0 issues...never dies.
#3. If it fidget with the heater controls and swing it from cold-hot sometimes it makes the heat kick in...but then it dies again sometime later


Next I'm going to try to replace temperature sender unit as suggested, and after that the coolant pump. I'll get to the bottom of this eventually . Winter isn't over yet!

As for the "cold weather" themostat....dealer had never heard of one for my car, and secondly my car had fantastic heat in the winter before all this happened. So I don't think that's it.

Rich...

RichW

Correct when re-circ light goes out heat is gonzo....cept in the #2 case in my last post. If I drive that car for 30-45 minutes the heat is perfectly fine. We haven't had any real warm weather for months so I can't speak to the last portion .

RichW

Is there a part # I can verify? Unless they blundered big time I doubt they put a tropical rad in the car, these guys do nothing but high end cars like BMW/Benz so they are pretty good. Didn't take it to "Neds Autobody". Where is the part # located on the rad? Anyone know?

RichW

Cabin heater performance does not mirror the coolant gauge at all. I can have 87C coolant temp, and 0 heat. And yup...something is definitely amiss , I'll keep replacing parts.....eventually I'll run out of coolant system parts to replace and fix it. More about the challenge/mystery at this point than the heat .

mleskovar

Maybe we're distracted by the motor operating temp. I'm guessing that one of your stepper motors or linkage is kaput and it's not mixing the air properly. Instead of mixing air after it stops recirculating it's letting in 100% outside air. The recirc works on 20 minute cycles but when it stops recirculating you can start the cycle again. Try keeping it in recirc mode and see what happens (have you tried that yet?).

C230 Sport Coup

I occasionally have problems with the controls.
Blow cold air when I'm telling it, HOT please.
Blows heat instead of cold!
Sometimes just turning the temp knob back and forth wakes it up so speak...
but try doing the recirc flap reset....
Uh...I think you hold defrost and recirc down till it flashes back and forth????
Try searching.
Also turn off the AC when running the heat.
You know by default it runs both...well, later on they went the other
way.
Mine has EC and Rest on the Button.
EC means Economy which means pushing turns OFF the AC. When you push the same button with
the car off, it will blow warm air, (though on a very low fan setting which is not adjustable)
for a period I think of up to 1/2 hour. Does yours do that?
Newer MB's (I think 2005 on) you have to push the button to turn ON the AC as
it is normally with Cars in the US.
Also, there's a seperate temp sensor that shows the temp on the dash, separate from the thermostat.
But run the recirc flap reset 1st. It's free!!!
Yes, I checked.
Re-Sync AC Recirculation Flap Reset-

Car running. Fan off.
Push Defrost and Recirc at the same time.
Hold them...the system will start to cycle, lights flash.
Cold air blows, hot air blows, and it goes between the floor, console and defrost.
It's determining the starting positions for all the air flaps and setting them.
Wait till it stops flashing.
Turn engine off, wait 30 seconds.
Problem solved?

This is one of those things you would do after the battery is disconnected like syncing the windows and sunroof.

Glyn M Ruck

I agree - I think this problem relates to the heating circuit only & not the engine cooling side. I think the engine temp is sufficiently stable. So it's a water flow problem to the heater heat exchanger - or an airflow problem through the heater heat exchanger (mini radiator) into the cabin. I think we should tackle those two.

mleskovar

That's where I was going with the blind...raise temp and see if cabin heat symptoms change.

Glyn M Ruck

????

mleskovar

Early in this thread I asked the OP to block off a portion of the radiator. I figured if the engine temp just moved up 20 degrees but nothing changed with the cabin temperature then we could rule out motor cooling problems. Here's my theory....the blending flaps aren't working properly. They are only partially blocking the outside air...causing slow cabin heating...and when recirc goes off it's 100% outside air, which cools off the heater core, which lowers the motor temp as well.

RichW

Well I did the "re-sync" as described here, and the defrost/recirc lights blinked back and forth, air started blowing from the floor, console, defrost; cycling over and over. It kept cycling forever until I stopped it after 5 minutes. I did this when the car coolant was at 87C and it never blew warm air and didn't fix the issue.

So far I'm thinking this lends some weight to the theory that the motor responsible for controlling a flap has died. How would I go about fixing this?

Also, to answer a question, if I place the car in "recirculation" mode if the air is warm/hot? It is. I'm not certain why this is the case, maybe it uses a different "flap" bypassing the problematic motor.

Rich...

Glyn M Ruck

Replacing stepper motors and arms is a terrible job. Half the dash has to come out - do you hear a recycling clicking noise from behind the dash? If so - broken stepper motor arm. Read the sticky 4th from the top.

mleskovar

This means one or more of the motors did not sync. It's supposed to go through the cycle and stop on its own.

QUOTE=RichW;3382769]..So far I'm thinking this lends some weight to the theory that the motor responsible for controlling a flap has died. How would I go about fixing this?..[/QUOTE]

Either the motor or the flap control arm. I can vouch for it being a tough job to replace, I've done it three times on my car - two broken arms and a bad motor. I couldn't get to the motor even after removing the entire lower dash so I disconnected it to stop the noise (right side defrost vent, seldom need defrost here ) I've been told I need to remove the upper dash to get to that motor! Your model has fewer motors than mine and you also don't have the fine charcoal cabin filters that get in the way of a couple of the motors/flap control arms. If you're adventurous DIY. About $750 US (I don't know how many Loonies ).

QUOTE=RichW;3382769]Also, to answer a question, if I place the car in "recirculation" mode if the air is warm/hot? It is. I'm not certain why this is the case, maybe it uses a different "flap" bypassing the problematic motor.
[/QUOTE]

Yes. PM me with your email address and I'll send you a pdf file of the system. Only the Germans could make something this complex. For example.... If you have it in recirc mode when you turn off the motor it opens the recirc flap a little bit so when you close the door with the windows up the trapped air has a place to vent allowing the door to close easier. Like the BMW window down/up dance. The only special tools you need to remove the lower dash are a couple of torx bits.

Glyn M Ruck

mleskovar - won't you please copy me that pdf. I just helped a friend do one broken arm on his C270 CDi without a manual. We really battled & I swore never again.

Will PM you.

C230 Sport Coup

These 2 things should assist you if you decide to DIY.
All thats required is lots of patience and tools. At some point somebody better cut and paste the whole mess, pics and all, and make a pdf before the pics gets lost as they so often do around here.
This is the sheeit.
Removal of dashboard - MBWorld.org Forums

Removing Mercedes-Benz W203 dashboard panels

OR
Just use the recirc function.
Then you're not blowing cold air in from outside.

Glyn M Ruck

I've pdf. ed the lot & saved every picture. Now the nightmare to compile it all. Anyway - no pics will be lost.