Figured I'd post here to see if you guys could help me get on the right track.

Purchased a 1986 190e-16v that the A/C did not work in (knew this buying it). After playing with the climate controls, I'm only getting air through the vents on the top (center and sides). Lastly, I'm not getting heat either.

Two days ago, I needed to have the car inspected anyway, so I had my mechanic throw dye in to see if it is leaking. It was converted to R134.

The compressor would not kick on at all. I replaced the #1 fuse with a 16a one because that is what the diagram says (used to have a blue fuse there).

Now the compressor kicks on but no cold air. Looking in the viewport behind the driver's headlight, I can see bubbles when I turn the system on in the car. Not sure where to go from there other than to see if it is in fact leaking.

I flushed the coolant system yesterday. While running the car, I turned on the heat and fan all the way up. No hot air coming out the side vents or windshield.
I also only pulled ~6 quarts of liquid out of the car (1 gallon container and a two quart container are full of waste). I do believe that both lines to the heater core were hot after running the car.

A little bit at a loss as to where to start from here. Obviously I have three separate issues...1) no heat, 2) no cold air, 3) inability to direct where the air comes from.

Given I can't control the air flow, I figured that was probably the most sensical to start with.

I started to follow this guide (Troubleshooting and Repairing the Mercedes-Benz 190D and 190E Tempmatic ACC Climate Control System. I started with the checking for vacuum leaks section.

I tested the connection coming off the engine that splits on the driver side under the hood and that holds vacuum when I turned on the car. I should probably go test the two connections on the other side of that Y.

Moving to the glove box, I pulled that out, and checked the aspirator blower. That also functions. I then proceeded to test the vacuum on the 4 and 5 port switchovers.

6 and 9 do not hold vacuum. I checked the switchover and they all hold vacuum according to the correct buttons that are needed to be pushed on the climate control.

This morning I still have no heat. I checked the power to the aux pump (connected it to the battery and it functions. Key on but engine not running and it functions. Engine on and it functions.). Went under the cowl and found this gem. Checked vacuum on the actuator and the line. Both held vacuum. I think the line did not with the engine running but I can't remember if it was that or if it was with certain selection(s) on the climate control.



Lastly, I checked vacuum on the stuff coming up the driver's side that splits. They all hold vacuum individually and with the y connected.

What the hell am I looking for with the heat? My understanding is that absent vacuum, that should allow heat to come through. So with that capped off like that, wouldn't it allow heat to flow unless there was something wrong with the valve itself?

If I understand correctly, I'm now going to have to remove the dash to trace this and see if there are broken connections and/or broken A/C vacuum actuators for 6 and 9, correct?

Any suggestions for how to resolves these problems? Am I on the right track?

An update:

Two of the vacuum diaphragms have tears.

Torn vacuum diaphragm is irrelevant to no heat, you should still be getting heat regardless of whether or not 1 or all diaphragms are thrashed. Go check the hose going to the driver side firewall and see if the heater core is bypassed or doesn't have some sort of valve added on to prevent coolant from going to the core. As for the AC, don't touch anything. You confirmed that the compressor turned on which means as of now all the electrical components and the refrigerant are for the most part within spec. Trying to adjust anything there could cause it not to turn on. Right now, you're just not getting cold air flow which could be the blend air flap. or some other issue unless the refrigerant is at the bare minimum to turn the compressor on, but not enough to cool the cabin.

As a side note for the torn pods, unless you're a purist, if you can't find those pods, then check other models and just mount them up. I think I snagged a few from a 124 and a 210 and mounted them up to my 201. If you can, reuse the metal legs, or you may need to do minor fabrication for the desired length. I also ditched the w201 bulky dual switchover valves for the 124. Much simpler and sturdier. Just wired everything according to the 124 controls by rearranging the pins in the connectors and plugged up the proper vac lines to the valve and that was it.

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1990 190E 3.0L

Thanks. I knew that these had nothing to do with the lack of heat. I'm gonna try flushing the system again and forcing water through the outlet hose on the heater core to see if something maybe got jammed up in there. The only other thing I can think of is that the valve has an issue. The vacuum tube on it was removed and plugged.

Before I ripped apart the dash yesterday, I checked the vacuum on the valve and the line and they both seemed to be ok. I ran the car but was unable to get hot water going up to the core. And the aux pump runs.

I'm not going to touch the A/C until vacuum system is back together. No sense in trying to chase too many things at once and creating more issues.

As for the vacuum pods, I found a guy in Tennessee who sells the diaphragms (Performance Analysis | Climate Control | Diaphragms | Blower Motors | Pushbutton Panels | Vacuum Door Locks | Autotemp | Cruise Control | Engine Oil Analysis | Mercedes-Benz Parts | Mercedes-Benz Club of America | Oak Ridge | Car Care - ACC Version I) so I'm just going to rebuild these.

Just debating if it makes sense to replace all of them while I have this apart or only the torn ones.

Just came back inside from draining the system again. Hit the radiator and reservoir with the hose.

Also pulled the valve on the inlet side of the heater core. I tested for vacuum and it is fine. However, I did notice that the leg which moves the valve inside was not connected. I don't know if that was something that was preexisting or something that I may have done inadvertently when removing it (although I have a hard time believing I did).

Given the vacuum tube was plugged AND this was previously a Florida car with a known A/C issue, my guess is that it was pre-existing. Particularly if the HVAC system is set to expel heat when things break.

It's raining now, so I'll head back out later to flush out the heater core and put things back together.

I flushed the heater core and reassembled the cooling hoses and heater valve. Refilled with more distilled water and ran the car (no thermostat).

Turned the heat to high, fan all the way up, and shut the fresh air vent. I now have heat.

One problem solved.

Another update.

This weekend I replaced the heater core with a new Nissens one. Dash was that far open so...might as well right?

I also got the diaphragms installed into the vacuum pods and replaced in their respective locations. Tested vacuum on all the lines, everything looked good, dashboard back in.

The instrument cluster gave me problems with no backlighting. I ended up unplugging it and removing the potentiometer. I disassembled the potentiometer, gave it a thorough scrub (made the parts shine) and reassembled. Now it works perfectly.

On the engine side, I replaced the timing chain tensioner since mine had the original and they were prone to failure. Also got my Euro headlights and corners installed. Unfortunately, I broke one of the headlight trim moulding mounting tabs upon their arrival (NOS Hellas...fml). I ended up plastic welding the tab back on after epoxy and plastic cement failed to hold it in place. The angle is just a tad shy of being correct, so I had to run a machine screw with a washer and nut next to the hole it should go in. I'll get a better one from the hardware store to make it look correct when I go next time.

I'm now having a different issue with the climate control. Despite vacuum being good on all the lines, still having issues. I'm not seeing the control rods actuate or the vents change when I select the different settings on the climate control unit.

Based on this guide (Troubleshooting the Mercedes-Benz 190 Tempmatic ACC Climate Control System) I checked the resistance on the plugs for the 4 and 5 port switchover valve. All but hole 1 on the right hand connector had the correct ohm reading.

I also tried to check the voltage on the feedback potentiometer as described in the guide and that was fine.

Lastly, when I handled the climate control unit, it would flicker and things would cut in and out.

Just not sure where to go from here (is the climate control unit itself bad? Is it the switchover valve unit?).