TOO LONG WON'T READ: Planar>Ebspacher because same, same, but bigger heater for less monies.
Alright so cat's out of the bag that I have a few of these in my 109's.
-In my stage 1 I have the 44D-12 Planar Russian heater Planar 44D-12 Diesel Air Heater Truck/RV/Bus/Boat cabin | eBay
-In my Series IIa 109 I have an Eberspacher Airtronic D2: Eberspacher VW heater Airtronic D2 external mount VW T5 & T6 | 292199018351 | eBay
Both trucks are 5 door 109's, both trucks are super drafty, *so if your truck is actually nice your results may vary*.
I have installed them both the same way with the exception of the fuel tank location.
-Units mounted on the rear wheel arch of the tub (see picture)
-wiring and fuel line routed through existing (maybe bored out?) tail-light wiring hole in the rear tub, or a hole in the rear tool box.
-Wiring for controller gets snaked and fed through to wherever you want to neatly mount the controller (on the stage 1 its installed cleanly on the wiper motor cover, on the series 2a its dangling near the heater unit because i'm a lazy pos)
-power source: draw 12v from your choice location, the harness that comes with the unit has an inline fuse
-mount the fuel pump near the tank, the pump has to be mounted at a specified angle (in instructions) and the pump has to be mounted lower than the tank (its a weak pump)
---On the Series 2a I have a custom made stainless steel tank that sits under the passenger seat
---On the Stage 1 I used the tank that came in the Planar kit and have that mounted under the hood (*hasn't caught on fire yet, but really should be relocated*)
-Air intake for the heater: draws in air from the cab
-Exhaust for heater: I am not a fan of drilling holes through tubs, so what I did was cut a piece of steel the height of the rear window, approximately 4"-5" wide, drill a 1.5" hole, and weld in a right angle NPT bung. After grinding down the threads on the NPT bung the exhaust tubing from the unit fits right on. This way if I ever need to take the heater out I can do so without having an array of large holes throughout the tub.
--Series 2a: right from the unit into the cab
--Stage 1: no-shame dryer hose running from the unit right to the front of the cab (*most unsightly but also *most effective)
Its a pretty straightforward install, but takes a lot of time to devise an improvise a clean mounting system for the unit and route and mount everything.
-the 44d-12 is cheaper than an eberspacher that's half the size/output. So for less money you get a SERIOUSLY MONSTER HEATER. It says it heats up to 31 degrees Centigrade, and I can confirm that is true
-having installed both I can confirm that the quality of components (fuel pump, duct work, wiring harness etc) is the same as the eberspacher
-having the dryer hose duct work is supremely ugly, but it gets the heat where we need it and it gets WARM. My dad and I are looking into a better duct work system.
-that f**king controller that comes with it is worthless. I have literally no clue how to operate it after reading the instructions several times. I've had other parties read the instructions and attempt function of the controller with zero luck. Every time we want the thing to go on or off is pure luck after mashing all the buttons. I am looking into fitting an eberspacher controller to a Planar heater because ease of use would increase 1000%
-quality component with great reputation, and parts availability at most semi-truck repair shops (one here in Omaha has reconditioned units in stock on the shelf, and stocks, or can get most any other part for it)
-Its controller is actually logical. Theres one button to turn on/off the heat, another button if you just want the fan on, and a simple dial to adjust fan speed. Its great!
-The particular unit I have for the Series 2a is a little small for the volume and draftiness of the station wagon. This could be resolved by reducing drafts and/or adding ductwork.
Buying package or buying piece by piece?
-buy the package. All of these little components add up super fast! I cut a length of exhaust tubing too short, and to get a replacement from the semi-truck shop was expensive. By the time you locate the components, purchase them, and have them shipped you could have installed the whole shebang two times over.
-It's also VERY nice to have everything you need ready to go and in front of you. You have the parts that you know work with your unit and correspond with the instructions you have. There are a lot of models of these heaters and it would suck to waste your time realizing part Part A doesn't attach to Fitting 8, or that you forgot a crucial bit.
-if you don't want a new package, semi-truck shops, some marine/rv shops, and probably eBay might have complete kits that include a refurbished unit rather than just a used one. Thermo King Espar Heater from Thermo King Christensen
Attached I have a few pics of the eberspacher, it was a quick and dirty install before the winter of last year that I haven't bothered to clean up. You can see the mounting location of the unit, the exhaust routing, and the location of the fuel tank and pump.
Hope this helps!