Can't get any hot air out of vents - PeachParts Mercedes-Benz Forum

WANT '71 280SEL · #1 09-01-2003, 11:14 PM

Today it wa very dreary. It was raining all day and was under 60 degrees. Tried to use my heat two diffeent times on the interstate and it would not get even slightly warm! The engine was at running temp and the fan was blowing as it should. Would the heater core be clogged? How do I test it? CCould anyone post a picture of what hoses should be hot? I heard something about a hose should be hot coming from it or something like that? Could my climate unit be bad? How could I test/fix it?
Thanks
David

Rick Miley · #2 09-02-2003, 02:13 PM

Just so you know, hot air never comes out the center vents. That is by design.

But if you have no heat from the side vents, defroster, or heater ducts, then it could be the climate control servo. That's the big plastic box in the engine bay that has vacuum, coolant, and electronic parts in it. Positioned right above the turbo. That ridiculous part is the achilles heel of the W116.

Check the routing of the heater hoses. The seller may have blocked or pinched them off for summer use.

300SDog · #3 09-02-2003, 06:26 PM

Quote:

Originally posted by Rick Miley
Check the routing of the heater hoses.

And at the firewall where heater hose connects, you might see valve actuated by vaccuum servo switch - I've got this on my manually operated heat control 116 - disconnect the vacuum controled switch and wire the valve/lever pernamently open.... this might give you heat throughout the Winter.

Otherwise, you can tear into the dash/console panel to bypass automatic climate controls...... disconnect ridiculous servo switches to hotwire valves and levers in position with duct tape so you've got defrost and dashboard heat set permanently on full bore that can still be regulated by operating heater fan motor.

Disconnected vacuum lines can be plugged with golf tees, and each should be marked with masking tape for easy reassembly in case you ever assault the gigantic project of rebuilding the automatic climate heat control system...... or, in case you need to restore the system for Summer A/C.

If there are fuses in fuse box labeled for the crazy automatic climate control switches, disconnect them too before you manually fix the system with duct tape and bailling wire.

Good luck - complicated climate control system repair is far worse than anything else that can go wrong with the entire car.

WANT '71 280SEL · #4 09-02-2003, 08:29 PM

I don' think that taping valves open, etc. is really an option with me. I wouldn't know where to start. I have seen inside the dash and all those valve things, no way jose. Is there a way to test the servo?
Thanks
David

84300DT · #5 09-02-2003, 09:46 PM

i trust you had heat control at max? if not then would suspect a bad temp. sensor.

WANT '71 280SEL · #6 09-03-2003, 10:57 PM

It will not blow hot no matter what I do. The temp wheel is at 85 (max) and defrost will be on. It will not blow even slightly warm. When it is on defrost my compressor comes on but I think it is suppose to. Also if I turn on A.C. the compressor comes on. I noticed once a couple weeks ago that the blower fan would not turn off. I turned off the climate control and it was still blowing air like it was on low or something. The compressor was off when that happened. I remember using the defrost about twice since I have had it, and it worked then. (about two weeks ago). I did add radiator stop leak to it about 4 days before the heat stopped working. My uncle said that he has heard of thta kind of stuff blocking heater cores. Is there a way to clear out the core or how can I test this servo or core
Thanks
David