Eberspacher Diesel Heater 801 controller wiring explained. 

Glad to help

Something along the lines of one of these would work uk.rs-online.com/web/p/toggle-switches/0316995/?cm_mmc=UK-PLA-DS3A-_-google-_-CSS_UK_EN_Switches_Whoop-_-Toggle+Switches_Whoop-_-316995&matchtype=&pla-307379923620&gclid=CjwKCAjwvMqDBhB8EiwA2iSmPCiw0OtoC9N2MqkA_vl_R1A5Su5oH7qnAIBOOkpJKcqwAcqeWCe6LxoC46kQAvD_BwE&gclsrc=aw.ds

Alternatively leaving the 801 heating demand on all the time so it acts as a permanent thermostat and putting a simple timer in series with the output (yellow) wire would probably be a lot cheaper and simpler. The timer would need a manual override switch though Loads of choices for simple 12v timers on eBay

Good evening. The rotary controllers are not very linear so can be a bit vicious, it's definitely a case of minute turns at a time! If you watch my longer video on how modulation works you will see it is done via comparing a relatively low voltage which is incremented based on the actual and required temp. The Chinese clone would have to emulate that to be compatible. I haven't played with any of the Chinese ones sorry.

@@CriftinsCampers OK, thanks Keith.

Ironically I had watched your video only a few days ago as I will be installing a d5 or a webasto thermo top in my Crafter for my calorifier as well eventually! These things can be a sod to bleed! Fyi I ruled out using mine for vehicle heating as well though when parked because of the power use needed by the heater and a manifold blower unit so for that I have a D4, you could consider using a PWM controller for yours though instead of that potentiometer which would save a fair bit of current and allow you to run it at a quieter speed. I think your Heater should fire up via a thermostat if it’s acting in the same way the controller does, afaik it is only the yellow wire that controls the on off of these heaters. I am not familiar with your particular controller does it have the blue/white wire for the diags function? it sounds as if the heaters going into lockout if you are having to do a power off reset maybe there’s some switch bounce in the thermostat somehow upsetting the heaters electronics, does the same problem occur if you try a simple on off switch instead of the thermostat? The hydronics heaters are fairly simple they are either on or off the only internal control is the power use once the water is up to temp, then they throttle back output from 5kw to 2.5kw. Eberspacher do sell a 701 controller for use with a hydronics heater but I am pretty certain the thermostat part is redundant other than to control the optional ventilation mode which is typically the vehicles heater blower fan. I have a heater matrix out of a black cab with a two speed motor and if I can make room for it plan to use it under the bed to heat the rear of the van however I will operate that via a thermostat and PWM controller I will simply be leaving the hydronic heater to do its thing I.e run constantly to keep the water at 80c, the idea being because of the excess noise and power use the heater, matrix blower and water pumps etc have I will probably only be using them whilst driving or during the daytime for water heating. Having experimented a lot in my workshop I couldn’t put up with the noise all evening. Hopefully your underfloor heating will however mean you won’t need the blower fan on very often. It’s worth mentioning the air heater controllers like the 801 use voltage comparison to control temperature modulation they aren’t really suitable for use with hydronics heaters there’s no actual on off switching going on, the yellow wire remains live all the time that the heater is commanded on and the difference between the preset voltage from the chosen thermostat output and the measured voltage from the internal or external temp sensor controls the blower speed and diesel pump I explain that in another video around 8 minutes in here ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ZhW1uscoy0Y.html

Thanks for the reply ,turns out you can’t control the boiler with a thermal switch , it needs to run off its own internal one. So I can only control what the water runs through ,let the boiler do it’s own thing

Hi Dave try unplugging the controller and plugging it back in but hold down both the arrow then select n0 think that’s the one you want and press the power button should stay on till you ture it of good luck

The 801 is clipped together so I guess you could rewire it directly, personally I wouldn’t bother, I would use the existing wires joined using solder and heat shrink sleeves or these things which are pretty good www.ebay.co.uk/itm/293992393392

Your welcome

I am not sure what or where you mean by a3 and a8, the standard oem harness should only have one blue/white wire and doesn’t have a blue/yellow wire afaik, it might be worth checking the wire colours in the harness at the heater end where the large connector is to see if they are still the same colours. Maybe the cables been extended with different colours used?

@@CriftinsCampers a3 and a8 is the pin numbers on the main plug on the heater I think i am sorted I just made sure the blue and white wire landed on the blue and white of the 801 controller thanks

The pump does not have a brown and white wire afaik, it’s brown wire goes to standard battery ground, look at page 39 here www.butlertechnik.com/downloads/Airtronic_D2_D4_workshop_manual_2.pdf

Possibly, read this but if not then a non timed version costs about £60 new and you will get a reasonable amount back for your version secondhand. www.butlertechnik.com/downloads/Eberspacher_80110003_controller_Installation_instruction_manual.pdf

Sorry no I don't but at a guess it uses a single wire Lin/Can bus to control the newer models of heater rather than separate cables, as the 802 is apparently not backwards compatible with the 801