98 E300D W210 Climate control problem
 

Problem:
Weak heater (climate control). No heat out of the center vents. Low flow, (but eventually hot) air out of the side vents.

Observations:
Engine temp display on the dash never exceeds ~65C
Error codes from the climate control pushbutton display:
B1231 ECT Sensor (B11/4)
B1234 Sun Sensor (B32)
(See Steve Brotherton's article for code access procedure: http://www.continentalimports.com/ser_ic40142.html )

So...
Does the ECT (Engine coolant temperature) sensor that is used in the climate control system also send the signal to the temp display on the dash? Which has failed, the thermostat, or the ECT sensor? both?

One more thing:
Individual flap test revealed that the right diverter flap (2) is not operating. All others passed test.

Thanks for your help,
Paul


Still reading? Here's some more info that may be useful:

Actual values after driving the vehicle for 20 minutes operating the heater with the outside temp ~25F:

1.In-car air temperature sensor:____22
2.Outside air temperature:_________-5
3.Left heater core temperature:____43
4.Right heater core temperature:___42
5.Evaporator temperature sensor:___34
6.ECT sensor (DFI, IFI):___________65
7.Refrigerant Pressure in bar:_______02
8.Refrigerant Temp Sensor (F):_____-1
9.Not Used (but has numbers?):_____-5
10.Blower control voltage:_________3.1
11.Emissions Sensor (voltage):_____2.1
12.Sun sensor (voltage):__________4.2
20.Aux. fan control current (amps):_0.0
21.Engine speed (x100=rpm):_______06
22.Vehicle speed (km/h):__________00
23.Terminal 58d (%Battery Volts):__00
24.Battery Voltage:______________13.1
40.Software Status:______________71
41.Hardware Status:______________34
42.Unlisted/Unknown:_____________72
43.Unlisted/Unknown:____________152

Other notes:
Fans feeding the interior temp sensors located in the overhead console appear to be working (will suck and hold a scrap of paper against the grate)

During the summer when operating the AC: Upon start up one vent might blow hot air while the others are chilly. Running the defrost for 30 seconds and returning to Auto usually gets it running properly again.

This won't help much but here are my observations when the system is set on auto:

If the climate control is trying to warm the car, heat comes out of the side vents, defrost and the floor - never from the center.

If the climate control is trying to cool the car, air comes out of the center and side vents.

I had a problem with the heat not coming out of the driver's side floor, only the passengers. Turns out that the control arm for the left diverter had popped off. It was an easy matter of taking the cover off, sticking my fingers up into the vent and popping it back together.

The random switch to heat from some of the vents in my car turned out to be a bad "duovalve" which is located on the aft, right side, inner fender, under the hood. Not cheap to replace, and there is a DIY article by Parrot of Doom or another about removing and restoring function to this item. Seems they get crudded up or something. I put a new one in. Problem went away. Also, recharged my A/C system and have good temperature control now. Before I had either full A/C or heat, sometimes both from different vents.

All this makes me yearn for the days of old, when you turned the heat up with a mechanical device that by itself operated some control valve or air diverter to increase the amount of heating. Same with the A/C - if you wanted it to lower the temperature more, you turned it up yourself. What the hell was wrong with that?

Jim

Can you manually override the blower speed and get good flow? Tap the center switch to increase the blower speed to max and see if your air flow increases.

You first need to determine if you have a faulty blower regulator or not. If it only works on low speeds it could be faulty. Also, when was the last time you replaced the cabin air filter? That can also block much of the air flow.

If your engine operating temp is really that low then you might need a new thermostat...does the needle in the cluster also stay that low?

Thanks everyone for your suggestions. I'll attempt to answer some of your follow up questions:

Evan, your description of the function of the heater (never any hot air out the center vents) makes me think my system is running (almost) normally.

Marty, my fan speed controller seems to function normally, and blows forcefully out the center vents when running the AC. The flow out the side vents when heating seems pretty weak, but maybe that's just how it is. I should check the cabin filter as you suggest since I have no idea when the previous owner changed it last.
Yes the temp gauge in the cluster typically reads about 65C, even in the summer. If my car can't make the coolant nice and hot, perhaps that's contributing to my heating problem. Just to confirm, does the dash temp gauge run off of a different sensor than the ECT (B11/4) that showed an error? I'd hate to change the thermostat if the temp gauge is getting faulty info.

Jim, thanks for pointing me to the duovalve. Here's a link to Parrot of Doom's maintenance description:
http://forums.mercedesclub.org.uk/showthread.php?t=18785
(Note that he is showing a right hand drive car. The duovalve is on the passenger's side of a US model)
Sounds like I might have an intermittent problem with my duovalve since my symptoms closely match everything I've read. I'm with you, Jim. I prefer to be part of the "closed loop" control system of the climate control, rather than leaving it to a computer chip!

Unless anyone has any other suggestions, I think I'll replace the thermostat, clean up the duovalve, and inspect/replace the cabin filter.

Thanks for all your help
Paul

Paul,

Have you tried cycling the system through all of it's positions manually? Take it off AUTO and using the selector switch, send the air to each vent, defrost and floor in turn for each side and verify that you're getting air everywhere it's supposed to go regardless of the temperature.

As far as engine temp is concerned, Mine runs from about 70C in the coldest part of winter, 15F here, to about 85C at around 100F ambient. Others can probably confirm if they are having the same experience normally. 65C does seem a little low but the air coming from that should still just about burn you with the controls set at maximum heat (HI).

One way to test the duo-valve is to unplug it. This sets it full open and should result in maximum heat from the vents. You could try reading the temp from the vents with a small rod thermometer and then unplug the duo-valve and see if the temp changes.

Oh yeah, I'm totally spoiled by the auto temp control. It's so nice to simply get in and go and have the temp perfect all the time with the occaisional temp adjustment if I'm wearing a heavy coat.

And you can confirm coolant temp by shooting the lower rad hose with an IR thermometer when at operating temp.

i KNOW you need an excuse for more tools......

OK, this morning I checked and the engine stabilized at about 72C with an ambient temp of 25F. At this temperature, it produced about 130F air from the side vents. When I stopped and idled for a while, I was able to get nearly 140F air.

When on "auto" mode, the air never does any more than "waft" out of the vents since it's divided between the defrost, side and floor outlets. This despite having the blower on full.

duo ...valve
 

I agree with Jim Smith........Remove the duo valve covers carefully wipe the solenoid's dry replace the covers.......the heater will work until antifreeze leaks back in ........I think its a T10 torx ......If its wet ...replace it!!
On my car, the flaps were doing strange things........After the valve was replaced all was well ...

I removed the 2 metal cans on top of the duovalve and ended up spilling a bit of coolant. The coolant seemed to come from the inside of the coil, as if there was no seal where the metal actuator in the solenoid contacts the valves below. Is it normal for the coolant to contact the inside of the coil? It appears as if a seal could be created between the can and the coil, as well as the coil and the metal plate below, completely containing the coolant inside. I saw no sign of coolant leakage before removing the can.

I dried everything the best I could and re-assembled it. I left the electrical plug off and will run it tomorrow with my meat thermometer and a borrowed-from-work IR thermometer ready to collect some data.

Thanks Evan for your description of the "wafting" flow from your vents. This is what I have as well- maybe I'm expecting too much? or maybe my wafting air isn't quite warm enough to be very effective. My kids (3 and 5) agree that the heater should be working better- they're always saying "daddy, will you turn on the warm breeze?"

By the way, Evan your Unimog looks like a pretty cool truck. I checked out some like it with Google. Maybe Terry is going to want to get one of his own when he makes it to Alaska (60deg N, 150deg W)...

a leaker
 

Yup a leaker .......better replace it ...........That air space should be dry, that is the electrical side!!
The antifreeze is shorting out the coils ....

Paul,

One way to get the classic "hot air blasting from the floor vent" effect is to simply use the air director switch to send it to the floor and close the side vents manually. This sends the entire air supply to the floor. Just set the desired temp up a few degrees higher than you normally would and it will still attempt to regulate it but it will only blow on the floor.

Thanks for the comments on the Unimog. It's kind of funny, it's the complete opposite of the 300. It is as unrefined in every way that the car is refined - one step up from a tractor!

OK, here's the temperature data after driving for 20 minutes with an outside air temp of 25 deg F, and the duovalve unplugged:

Left and right vent temps: 110-115F
-Lower than Evan's reported temps of 130-140F
Lower radiator hose: 35C
Upper radiator hose: 56C
- Terry, does this confirm that my thermostat is opening a little too soon? if it was operating properly would the hose temp be closer to 80C?

I picked up a thermostat today and had every intention of installing it tonight, but then my cozy house sounded much better than my 25 degree garage. Maybe tomorrow.

I hope this will fix my weak heat problem. Next on the list is the duovalve, but I imagine it will take a few 90 degree days to motivate me to tackle that one!

Thanks everyone for your input. I really appreciate the time you've taken to post replies and collect info from your own cars. I'll update the thread as I make repairs and see the results.

Paul

The hose temps seem low but living in Sunny Calif I've never driven mine in 25F weather either.

What was your engine temp gauge showing when took those readings.

Hi Terry,
The gauge on the dash read 65C when the hose temperatures were measured.

I purchased a thermostat locally, and it doesn't seem to be the right one. The new thermostat comes with an o-ring while the old thermostat that came out of the car has a seal ring with a c-shaped cross section that is formed around the largest diameter flange on the thermostat. See the attached photos. (new is on the left, old is on the right).

I'm afraid the o-ring seal wouldn't do the job and would allow the other side of the flange to leak where there is just a brass-on-aluminum interface.

I tried 4 parts places, and 3 couldn't get the seal and the other one supplied an o-ring.

Note: there was a thermostat change on these vehicles that required a new housing as well. My car already has the new version. See post #5 on this link for more info:
http://www.peachparts.com/shopforum/diesel-discussion/206009-1999-e300-606-thermostat-replacement.html?highlight=e300+thermostat

I thought a thermostat would have been pretty simple. I guess I'll deal with the shipping delay and order one from Phil, he'll get it right!