Heater not working

[Wobdog]

I need some advice guidance trouble shooting my heater on my 1971 2800CS

• Main blower works and blows air
• When I move the temperature sector to hot and move the air distribution lever to the far right I can feel a little heat on upper vent to the wind shield.
• I never feel heat at my feet or middle vents
• Cold air lever does not seem to make any difference
• AC works great

Mike

 

[adawil2002]

Did the previous owner install a heater bypass valve?

It would be near the brake booster on the engine side. May be a thin rod to toggle between heat & off.

 

[Dick Steinkamp]

Did it just stop working or has it always been like this?

If always, check for missing or disconnected paper duct tubes. (A pain to get to and/or replace)

 

[TomHom]

Maybe there is air inside the cooling/heating system and it needs bleeding? The air bleed you will find at the thermostat.

But note: you should lift the front of the car in order to bleed all remaining air from the heating system.

 

[Ohmess]

Two comments:

I use a little different bleed technique - see here: https://e9coupe.com/forum/threads/n...rsus-guage-reading-position.40069/post-348606

And there will never be hot air coming from the center vents (unless it is very hot outside). These bring outside air into the cabin. Cold air lever controls whether or not air is allowed in through these vents. All of this is separate from the heater.

 

[Wobdog]

I did get the heat coming out of the window vent so thank you for letting me know that no heat comes from the center vent

 

[Ohmess]

Moving the air distribution lever to the far left side does not give you any heat at the floor? This lever merely distributes the air flow. If you get heat in the defroster vents, you should be able to redirect that heat to the floor.

 

[eriknetherlands]

It is kind of strange that you do get heat to the windshield, but not at your feet.
I am a bit puzzled by the fact that you write that you get just a little heat to the defrost vent; it should be more then just a little. This to me is indicative of a system in need of a bleed.

If the bleeding doesn't help, then I am left with thinking about the more mechanical stuff:

The distribution of the air passing through the heat exchanger is done -logically- behind the heat exchanger. So if air can go to the defrost, and not to the feet, it could mean a number of things:
1. obstructed airflow to the feet would mean blocked ducts- i can think of two reasons:
1a. In the heater unit there are various foam pieces, even textile sheets; if they have come loose it may have obstructed airway?
1b. Perhaps the attachments of the cables have loosened? check: Could it be that when you move the selector lever, the feet flap(s) aren't changing position and simply remain closed? You can stick your finger in the outlets from below, and feel if the flaps move when you operate the selector lever. The feet vents are each closed with a plastic flap, operated by the rigid bowden cables. Pls refer to the DIY on the heater box (https://e9coupe.com/forum/threads/diy-heater-unit-rebuild.38896/post-333882) with images and explanations of the system to identify the lever that you can check: Lever #3 is connected to wire #3, which in turn is connected to a wire passing from right to left through the bottom of the box.
2. warm air leaking away before it reaches the feet (missing tube sections on the side as @Dick Steinkamp mentioned?)

some images of the routing of the bowden cables:

Erik