Heater Won't Blow Hot

[BMWtyro]

With both HVAC dials turned clockwise and the top and bottom HVAC levers slid to the right, our 8/84-built 633 won't blow hot air out of either the floor ducts or the defroster ducts. Strangely, I seem to get a tiny bit of heat to the floor with the center lever slid to the right. The heater blower blows like a hurricane and the hot water hoses into and out of the heater core are very hot (even though I can't get the rebuilt heater control valve to "click").

Have I left anything out? if not, please offer some suggestions; it's gettin' cold 'round here.
Jeff

[bpoliakoff]

Is air coming through, just not hot maybe warm? If so. your fresh air vent is either not sealing or stuck open . Other possibility is maybe the diaphragm in your heater valve is shot.

[Brucey]

the first thing I would do to check that the heater valve is signalled to be 'open' when you want it to be hot. With the ignition on the valve should click (not very loudly, you won't hear it inside the car) when the heater dial is turned between hot and cold. If this doesn't happen there is a fault in the control circuit or a fault in the valve. You need to test the signal at the valve, with a meter, a (small) dummy load or a 'known good' valve.

If the heater valve is opening and you have hot water flowing (which seems likely from your description) then the lack of air in the cabin is probably to do with the flap controls; early cars had manual flap controls and later ones had electronic flap controls; either can go wrong in different ways. Both have a system for diverting the air when the AC is 'on' so that might be something to do with your problem.

cheers

[EmperorNero]

You'll want to verify that the heater valve is functioning. If it is, then you're gonna have to open up the dash and find whatever door/flap is binding or stuck.

[GCR]

the first thing I would do to check that the heater valve is signalled to be 'open' when you want it to be hot. With the ignition on the valve should click (not very loudly, you won't hear it inside the car) when the heater dial is turned between hot and cold. If this doesn't happen there is a fault in the control circuit or a fault in the valve. You need to test the signal at the valve, with a meter, a (small) dummy load or a 'known good' valve.

If the heater valve is opening and you have hot water flowing (which seems likely from your description) then the lack of air in the cabin is probably to do with the flap controls; early cars had manual flap controls and later ones had electronic flap controls; either can go wrong in different ways. Both have a system for diverting the air when the AC is 'on' so that might be something to do with your problem.

cheers

The heater valve is constantly open, unless voltage is applied to it, so unplugging it and checking for heat is how to test it.