hey all, my heat has started to do something funny. if i'm driving along and the heat/cold dial is set to hot and i press any of the buttons to turn it on, nothing comes out of the vents. the coolant temp. goes down a notch so i know that everything else is working except, i assume, the fan. however, if i set the dial to AC or cold and turn it on, everything works great. i then spin the dial down to hot and i have heat with no issues for the duration of the drive. what gives???

83 300D.

__________________
1985 300D - 1984 Euro 280E AMG Clone (SOLD) - 1978 280CE (SOLD) - 1983 300D (SOLD) - 1981 300D (SOLD)

It seems to me the cold engine lock out switch is the culprit (located on the thermostat housing). You might want to check to see if the connection/wiring is good. Or replace the that switch.


Here is a procedure to check the blower.











http://www.programainc.com/files/blower_speed_regulators/33910.pdf

http://www.programainc.com/files/31285.pdf




.

__________________
1983 123.133 California
- GreaseCar Veg System

first, thanks for the info deliveryvalve!

unfortunately, it's getting worse. today, i drove for about eight miles with no heat and/or no A/C. the CCU is no longer responding to any buttons that are pressed. i can hear liquid squooshing around behind the unit, and the car takes a bit of a hit in power when i switch to full heat, press the hi button, and click any of the buttons to turn it on. so, i know something is responding, just nothing is being blown out of the vents. no heat, no cold, no nothing.

after about eight miles, it decided to work out of the blue. once it decides to start working, everything works perfectly. this was after eight miles of me pressing every button, spinning the temp dial, and pressing the auto, low, and hi buttons over and over and over.

what does this sound like? where do i begin? is it worth taking the unit out to look at it? (i have no idea of what i might be looking at anyway ). does this sound like a blower problem or a CCU problem? help!!!

EDIT: forgot to mention that the other day when it was on the fritz i gave the side of the console a good, frustrated punch and it started working. must have been a coincidence though because today punching it did nothing.

__________________
1985 300D - 1984 Euro 280E AMG Clone (SOLD) - 1978 280CE (SOLD) - 1983 300D (SOLD) - 1981 300D (SOLD)

Other than the liquid swooshing around I'll suggest checking the unit for cold solders.

__________________
83 SD

84 CD

Could this be a vacuum problem, not opening the heater vents. Can you hear the vents opening when different buttons are pressed? Sometimes a clack can be heard.

__________________
1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom

so, what's in the list of everything that can go wrong because of a bad water temp switch?

i talked to oldsinner via pm and he was telling me that he wasn't getting any hot glow plugs when his was broken because it was telling them that the engine was already hot. i'm hoping that this is possible for me as well as i've been having a ton of glow/starting problems and now discovered this heating problem as our temps went down.

can this all come back to a bad water temp switch?

__________________
1985 300D - 1984 Euro 280E AMG Clone (SOLD) - 1978 280CE (SOLD) - 1983 300D (SOLD) - 1981 300D (SOLD)