OK - I have a few problems and am going to start with this one after fixing some others already - wanted to know where you guys think I should start.

The car blows heat all the time, regardless of temp. dial. The AC is not hooked up, so that is a non issue (belt off compressor and it is not plugged up), but would like to just get it to vent normal air temp instead of hot for starters.

Center vents don't work

Should I start with the heat issue or the center vents?

I have read that the monovalve on the passenger firewall might be the culprit. How do I test this? Should this be my first item of interest or should I resolder the CCU?

I've read a lot in here about the various CC problems already but would like some direction from someone with more experience.

Thanks so much.
Tom

If you lived around here you would fix the heat first.

Make sure you are getting 12vdc to the monovalve solenoid with the key on. If you are not start troubleshooting from there. Pull the monovalve insert and inspect the rubber. If it is busted or the solenoid portion does not cheak out with an ohmeter then replace it.

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Jim

is the wagon in question? Did I just miss that info?

Jay.

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On the road, currently:
'83 300D (German spec.) 168k mi. - - Wolfgang (tucked snugly away for the winter!)
'87 300D 375k mi. - finally went over to "The Dark Side"
'87 300TD 225k mi.
Cannondale 66cm CAAD5 w/Campy/Jamis Aurora
Hujsak Custom Fixie/Landshark Track Shark Custom/Ahearne Custom 29'er

With the CCU, I should be able to tell if it needs soldering, mine had some burned connections that caused it to make clicking noises, and turn things on and off by itself. Once I resoldered those spots it works great.

The center vents, if the center vents aren't working you probably have vac leaks. The center vent accuator is tough to get to. It's right behind the center vents. But you can test it without removing it. That will tell you if that is the culprit or not.

AC, fixing the center vents(vac leaks) and resoldering the CCU are cheap. While restoring a AC can be pretty expensive. I've too have a ,possibly, siezed compressor, a torn switch wire, and a leaky system. I have priced all it out at $500-$600. Thats just parts and me putting it all together. AC sure would be nice when it's 105 here in the summer.

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Find the ACC section in the FSM (secion 83 know it by heart ) and start with the tests. GL and be ready to have multiple religions to call upon.

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Thanks everyone. Its an 81 Model - I failed to mention that - sorry. I sat in the car for about 15 minutes when I got home with it running just to test it thoroughly. It seems that all the buttons are doing what they are supposed to be doing, except for the center vents. When you hit the button for the center vents (double arrows I think it is) - it blows SUPER hard through the outside vents, which leads me to believe the actuators are working for everything but the center vents (ie with them closed, the only outlet for all that air is through the two outer vents). Does that make sense? Could the vac for only the center vents be screwed up and everything else be ok?

I can't get a good feel for the temp. wheel - it SEEMS like it is not heating as much when I turn it down cooler now, but still doesn't feel like outside air, just slightly less than burning hot, and it definitely goes to full heat to the floor when I turn it to MAX heat - I'll still check the monovalve but I think the CCU itself is actually working ok - now clicking or anything.

What ohms reading should I get on the monovalve??

Working on this thing is kind of an enjoyable challenge - somewhat - I guess I may change my mind once I really get into it.

BTW - nice wagon Biodiesel.
Yeah, I'm torn between not worrying about it as winter will be here soon and it doesn't bother me that much, but I would like to get it working just on the principle.

I plan on spending a little money to fix the AC, get mechanicals/maintenance up to date, and fix a dent on the tailgate and driver quarter, but everything I can do myself I'm gonna do.

AC in everything is soo doggone expensive to fix. My camry's AC broke and I haven't fixed it yet either. I hate it when that crap breaks.

Thanks!

Yup, one actutator can go bad. If your lucky it is just the rubber connector that is leaking, but it is mostlikely the actuator. Pull out the glovebox, get a MityVac if you don't have one, and you can test the actuator directly and you will know if it is that or not.
The trick it replacing it. If you have small hands and are patient you can apparently possible to get it out with out having to remove the dash. I had to take mine out. Also unless the plastic of the actuator is cracked or the lever arm it no working I would buy replacement diaphragms instead of buying a whole new actuator. It's much cheaper.

Here is where to get the diaphragms.
http://www.autoluxmbz.com/

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Sometimes the vac pod is good and works, BUT the connection between the pod and the center vent flap is disconnected (like mine was). With the pass side kick panel removed you can reach up and feel if the pod is working or not.

Bio...did I understand you right? You replaced the cener pod WITHOUT removing the dash? If so, I stand in awe! Neat trick. I could not even get the flap reconnected to the connection link....I could "feel" what needed to be done, just could not getterdone.

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Mark
1983 300TD Wagon
Even a broken watch is right twice a day

Well, I think the monovalve is ok. After spending some time with it, it just takes a while for the hot water to clear out of the system and go back to ambient air.

It appears the CCU is working ok as far as the heat is concerned. Now I want to know if it is sending the proper signal to the compressor and all that. Problem is I see some unplugged sensor on the drier and an unplugged connector near the compressor. Where can I look to see how the electrics are hooked up to all this?

I can hear a click from the CCU when it activates the heat, but I don't hear anything when I turn it to cool. Should I be hearing something?

regarding testing the system, do you have to have the MB analyzer tool thing that you plug into the AC main unit? That think is like 500 bucks.
Thanks