installation order - heater / ac

[rsporsche]

okay guys - its about time to start installing the heater + air conditioner. since i didn't take them out, i'm a little lost on order of install, and since my track record shows that i take 1 step forward / 2 steps back. and get to practice / remove + reinstall things a couple of times.

any advice would be appreciated

 

[Dlc]

Scott,
the heater box goes in first and is sitting at the firewall.
The AC evaporator box goes in second and sits in front of the heather box.

The AC box sits on a base plate bolted to the transmission tunnel.
The two systems, once in placem need to be connected via the infamous intermediate piece.
Before you put in the intermediate piece and the heather front/air outlet, remember to put the probe from the temp switch into the target location into the evaporator.

You have some nice pictorials here:

Thread 'DIY - Heater unit rebuild'

Sep 22, 2021

My pay back to the forum; here's my approach to rebuilding the heater box from my E9. Not sure how this compares to e3, but let me know and I can possibly merge.

I'll likely chop it in roughly three pieces; removal, disassembly, repair and rebuild. I haven't installed it yet myself, so i can't do any pics of that .
I will add sections in the coming days, depending on how boring my meetings in the office will be....

Cost & time estimation: About 450 euro and 30 hours.

- Re-cored heat exchanger: 231 euro
- Re-zinced parts (done with other parts, so I just take a part of it: ) 30 euro's...

• eriknetherlands
• Replies: 31
• Forum: DIY - Do It Yourself Articles

• 
• 

and here:

Thread 'Re-installing the AC evaporator'

Sep 13, 2022

Part 1: Preparation:

Here are the parts you will need:


Throughly clean the air box and reinstall fresh felt around all of its leading edges to ensure good air sealing. I got rid of the foam pad which had deteriorated and did not seem to do that much anyway.
I later added a few strips of dynamat to tone down the vibrations





Disassemble the Evaporator to clean it up, removing all rotting foam and accumulated dust



At this point I would highly recommend getting @Blinkling ‘s upgraded evaporator guts. It’s...

• Bmachine
• Replies: 9
• Forum: E9 Projects and Restorations

• 

Post in thread 'a/c drain not draining'

Aug 4, 2017

This rubber funnel only shows up on the E3/12/24/21 and 28. It perfectly seals and funnels that area to gather the condensate. Notice the nice cut-out in the front to allow the plastic drain protrusion of the AC box to slide over it and into its center. Still available as of 3 years ago. Also a foam cylinder interfacing between it and the tunnel sheetmetal. Although photos are from E3, all work well on the E9...

• Luis A.

Heater box:

AC base plate:

good luck with the install - a job that requires patience and persistence!

 

[rsporsche]

many thanks Dominik ... i will be using this in the next few days. i have the pieces, so this is very helpful

 

[HB Chris]

I drilled a small hole in bottom right corner for the probe and could feel it go into the fins. It will fall out in my experience.

 

[Dlc]

Scott - in this post you can see where the evaporator, intermediate piece and heater box sit:

Post in thread 'BMW 2800cs -> S38b36 project'

May 20, 2026

Progressing further, installed the interior heater housing and evaporator housing to see how the AC lines match up which are from an old AC installation and will be used as a reference only before installing new ones.

Was a bit surprised by the fact that the intermediate part on top of the evaporator housing was so much ‘blocked’ by the edge of the evaporator housing as you can see in the pictures. Should be normal I guess? And I still need to re upholster the edges of the intermediate part.

• BMW3.0CSi

•