e34 heater woes - no heat below

[DaveCN]

Ok,

I tried searching to no avail. Here is the problem I have.

I can get hot air blowing through the vents and the defrsoter vents, but cannot get any to blow out of the floor heat vents.

Looking at Bentley, I found it less than helpful. It merely says - there may be up to 10 stepper motors and very generally describes how to replace them. It does not show locations nor does it have any electrical etsting procedures suggested.

1994 525it US model.

Do i need to just rip the dash out and start guessing or does anyone have any suggestions?

I figure it has to be the flaps in some manner - either the controls are not working or the motors.

Anyone?

-Dave

[Tiger]

The heater valves are located on the driver side of the engine compartment right on the firewall ... You will see a black cover on the top and if you peek on the side, you will see all sorts of heater hoses.

I have had that happened once... The valves got stuck. What you need to do is take the cover off and whack each valve with a hammer to see if it is loose. You must do this with key in on position and heat set to max... Whacking it will loosen that stuck valves.

If it doesn't work, you are gonna have to loosen the covers... bunch of tiny torx screws... and do the procedure above... This however, will require the engine be cold or no pressure in coolant system. Tighen the screws back up once fixed.

[Tiger]

Ahh my mistake. Didn't read carefully. Center vent must be shut off completely to force heat out of the bottom vents properly. Defrost is normally shut unless you got icing problem and then just open half way or less.

Center vents are the least restrictive vent and thus the air wants to go with the path of least resistance.

[Robin-535im]

On my 1990 535, the defroster and mid-level vents are actuated with a cable, but the foot vents are electrically switched. Since you have hot air flowing through the car, I would guess it is a flap somewhere that is not opening. Unfortunately I don't have a magic bullet in mind besides good old investigative surgery armed with your multimeter.

The electrical schematic in Bentley is a good starting point, as is the factory service manual which you can probably get on Ebay. Comes on a CD and it's BMW's official manual. There is also an electrical troubleshooting manual that has all the info you'll ever need. Other than that, maybe someone else can post with a more directed answer...

[DaveCN]

Thanks for your response, Tiger. Not doubting you, but I am not sure we are comparing apples to apples.

I get plenty of hot air through the dash vents and the defroster, I just can't direct it to the floor vents.

Seems to me it is in the dash and how the flaps direct the air - not a lack of coolant going into the dash to the heater core.

[DaveCN]

Robin,

Thanks to you too. I am leaning towards your suggestion.

I have Bentley - and the HVAC section is unhelpful, but I have yet to review the electrical scematics. I also have the facotry electrical manual.

Looks like it'll take some exploratory surgery.

:-P

[Ross]

The good news is all those servo motors are the same as I recall, so easy to switch for diagnostic purposes.
The climate control module could be screwy too, often it's just bad solder joints.

[Robin-535im]

I've heard that some or all e32's had HVAC servos containing some kind of bearing lubricant that was corrosive to plastic. The servos would leak and the goop would get onto the plastic mounts and they would then fail - necessitating a replacement of major parts of the dashboard.

EDIT - back to the issue at hand, I tried my HVAC just now and the floor vents will respond to the heater controls regardless of the other vents but there is a delay in the action, it takes a few seconds for the air to get to full after you switch it over in the controls. Makes me think it's electrical and/or vacuum that makes the vents open.