Strange HVAC issue onmy 98

[BlackIceLSC]

I know on my Dad's BMW, and another customer's 3 series, the HVAC system would not work if the Ambient Air Temp sensor was not working.
We found on the 3 series it was unplugged, and on my dad's BMW, it was hanging down from a parking block incident. When they were repaired, the HVAC worked.
Thinking I might try this.

My AC blows ice cold in summer, just no dang heat.... now, more than necessity, it's a matter of a challenge to solve the mystery.

Anyone else ever have the AMBIENT AIR TEMP SENSOR cause their HVAC to not work?

ALSO...when I run a EATC self-test, it stops after about 20 seconds and displayed ALL functions (the digital image) but never shows the "888" for complete, or any codes.

 

[BlackIceLSC]

after some thinking, I realize that it is unlikely a faulty ambient air temp sensor since my EATC seems quite accurate when displaying the "outside air temp".

Just looking for your thoughts.

I received my new gray arm from Ford for $8.50 yesterday. Can this be changed without removing the dash?

 

[steve]

the outside and inside temp sensors are separate.

 

[billcu]

There is no valve that stops the coolant flow into the heater core on this system (my 78 MGB has one though). That's why it uses 2 doors to close off the heater core during AC operation.

The temp sensors have nothing to do with your problem if you can make and see the blend door actuator move in both directions from stop to stop.

If you think the top door might be broken internally, you can remove the blend door actuator and put a 1/4" drive extension in where the actuator goes, and turn it, to open and close the door. You should feel it and hear it, open and close like the lower door, against gravity, but this one has a little more travel.

Edit: I meant 1/4" drive extension, not socket.

 

[BlackIceLSC]

Can I replace the gray arm without removing the dash?

I am trying to find out as best as possible WHAT is broken before yanking the entire dash, so I can *hopefully* avoid yanking it twice.

- - - Updated - - -

the outside and inside temp sensors are separate.

Thanks Steve

I have narrowed it down to the black door actuator possibly being stripped INSIDE the HVAC box, since I can see the OUTSIDE of the actuator and black arm make full movement/sweep when temp is changed, yet still no HEAT

 

[driller]

I wonder if you could get a cheap USB video borescope camera in there to see if the door is moving???

 

[BlackIceLSC]

This is brilliant....I have one at the shop. I'll try to journey inside the HVAC BOX and SEE if I can see.

 

[BlackIceLSC]

update:
I ventured back in yesterday with help from my brother -in -law for an extra set of hands and eyes.

took the instrument panel trim, message center button tray and screen out and lowered the glove box.

YES, they gray arm just pops out with a pry-tool.
since the black arm appears to rotate normally and is not broken, we surgically attached the metal rod to the black arm and lowered it down to the gray arm...while trying to attach it to the gray arm, we noticed the angle was off...the metal bar was not parallel to the HVAC box.
closer inspection showed the blend door actuator is actually pulled away from the HVAC box...I can move it in and out 1/8"...seems it broke off the HAVC box and must not be closing the top door all the way.

I re-assembled the trim/message center and realized I now need a replacement HVAC box on stand-by for when I yank the dash in case the box is damaged.
I am not pulling the dash twice.
every time I remove trim pieces, something else breaks(little tabs, cracks, etc)

I'll go without heat until I find a complete used Gen 2 HVAC box, build my set up like Jeremi showed, and then just swap the whole thing with new heater core and all.

 

[Lvnmarks]

I'm sure Carlos (racebronco2) has a few.

 

[BlackIceLSC]

I've bought from him before...I'll inquire.