Sorry to start another thread but this thing keeps biting me in the rear. (1985 300SD)

Car is up to operating temp. Set ACC to just under max heat. Cool air from vents. If I put to max heat same thing. It seems like more heat from vents below than from dash vents. Now I hit the Economy button and keep heat set at same place. Much warmer now.

I rebuilt monovalve, flushed core and checked aux pump. All seems OK.

Something funny I noticed. When I set the thumbwheel for heat and hit any of the ACC buttons other than economy, I can hear the AC compressor clutch kicking on. When I hit the economy button with the heat on the air gets noticeably warmer and the compressor kicks off.

Is my air conditioning kicking on the same time as my heat? I am having difficulty with this. I was going to try and unplug my compressor and see if my heat works correctly then.

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

Everything that I have read says that the A/C on these cars is only completely off in economy mode. Otherwise it is set to run a little or a lot to decrease humidity. The lack of heat to overcome the A/C can be related to bad thermostat, plugged heater core, broken/ripped monovalve diaphram, or auxiliary heater pump problems.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

Someone had told me that before but I wasn't sure they were 100% accurate. I checked everything I can think of but the heat is still really weak. I was thinking it may be the push button unit but all the buttons seem to work as far as duct control and blower speed. I don't think it is the sensor either because the heat is still weak with the thumbwheel set to max heat.

How quickly does everyone else's SD warm up? Maybe my car is slow to warm up. New thermostat?

__________________
'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

If you only want heat, don't select anything but the economy mode. The other selections are supposed to engage the compressor.

You say up to operating temp - what is that? My SD stays around 82C fully warmed.

If it's not that warm, try a new t-stat.

If it is, check or replace monovalve again (unplug to get flow) and check aux pump again. Otherwise, you might have a clogged heater core.

The ACC turns on the compressor in all modes except econ. Sounds like your A/C works better than your heater!

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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer

It was like 45-50 degrees F when I left work this morning. I started the car and let it idle for about 3-4 minutes. I then did some around town driving for the next 10-15 minutes or so. I had heat but it wasn't really hot like it should be. When I got home the temp gauge was still below the normal operating temp. (80)

__________________
'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

Firstly, the aforementioned posts are correct..........the a/c is engaged in all modes but economy.

Second, the 617 does not put out much heat until the gauge gets over 60°C. and even then, the temperature is not all that hot.

Third, if you drove it around town.....at low speeds.......it does take awhile to warm up. A properly working auxiliary pump might assist in getting heat through the core faster. IIRC, you've verified this already, correct?

Fourthly, remember that the temperature inside the cabin is 50°F. before any heat is produced. Accordingly, the system will restrict the heat from the monovalve because the temperature in the cabin is approaching the setpoint (70°F.). Move the dial all the way to the stop to evaluate the capability for heat........independent of the dial setting.

And finally.........do we really need another thread on this.........you've already got one going IIRC? I might just merge this with the old one.

Your third point= I thought it strange that after 20+ minutes of around town driving that my car was still not warm. yes I tested the aux pump. (I stated this earlier in the thread)

Your Fourth point= I stated earlier in this post that I moved the thumwheel all the way to the stop. It should throw heat no matter what the temp inside or out.

Your Final point=There is no old thread. There WAS some redundant info so I took your advice and deleted it. I feel this is a valid thread because I am having strange, unresolved issues.

I don't know if I am just in a bad mood or not but I am getting a little pissy. If this thread is bothering anyone else feel free to delete it or lock it. Or I will do it myself.

My apologies ahead of time, I am on the rag.

__________________
'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

I thought the dash vents weren't supposed to put out any heat? They never did in my W126 280 SE or my 300SD. I just close 'em when it's cold.

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1982 300SD