Eberspacher 801 question.


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When i apply power to my eberspacher d2 with 801 controller, it defaults to heating off, you need to press the button to start heating. i have a gsm operated remote relay, so I would like it to go into thermostatically regulated heating mode as soon as it receives power, so when I text my van to turn the heating on for 30 minutes it is toasty for me getting in, but because you need to press the button every time this doesn't work if you wire it in the normal way.
1 way to bypass this is to apply 12v to the yellow wire, the problem is this bypasses the 801s temperature regulation, meaning sometimes you get into the van and its 35 degrees and you are sweating so the preferrable outcome would be to reprogram or rewire the 801 so that when you apply 12v to the small red wire it defaults to heating running, with the thermostat set to whatever we left it at.
Is this possible?
If it isnt the only other workaround I could think of would be wiring a seperate mechanical stat or battery operated domestic programmer and putting it in series with my gsm relays connection to the yellow wire.
Any thoughts or suggestions?


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I have the 801 with diagnostics and didn’t think it was programmable, at least not seen anything about programming them. I gather the controllers that come with the Chinese heaters are very programmable, was told the Eber stuff is like going iPhone and the Chinese more like Android.

I suspect Dave May have some ides but may be worth looking at one of the Chinese controllers


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I might connect one of these https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/163870018943 in series between my gsm relay and the yellow wire and set it to 27 degrees or thereabouts, just its extra gubbins, sometimes simpler is better.
The chinese controllers aren't compatible with the eberspacher data bus, much more of the processing happens on the controller on the chinese ones where most of the processing happens on the heaters pcb on the eberspacher, other than pulling codes the eberspacher one is mostly just an on-off call for heat type thermostat.
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Not got any experience with remotely controlling the Eberspacher Heaters, so can't help with that directly but have some ideas that could be thrown in for considerations.

A very good resource for Eberspacher Heaters is on the Letonkinois Varnish website, and there is a page on there that discusses potentially using two controllers on the same heater (see here - https://www.letonkinoisvarnish.co.uk/eberspacher_control_4.html). Now there is not a great deal of info there, and the Eberspacher info was developed on there by two brothers, one of which has sadly passed on. THe two brothers had different expertises in the heater so I don't know if the surviving brother knows the controller electronics or not?
However the above link might help spark some ideas?

Next idea - add in an external temperature controller that will control the 12v application to the yellow wire, so once the room temperature has hit the [external controllers] set temperature, the 12V to the heater is cut and the heater presumably will turn off. This could be the most straightforward option?

You would have something like the following:
  • GSM Remote Receiver ====> Enables 12V on wire ====> Relay on Temperature Controller ====> Yellow Wire to Heater
So the Yellow Wire will be at 12V if BOTH the GSM Receiver has got a ON command AND the Temperature is below the set value.

I have done the above kind of setup on a heater installation of one of the Chinese Clone Heaters with the most basic mechanical controllers....
Used a Remote Garage Opener fitted with a SIM card - That would go on and off in response to Texts;
The control output went to the relay input of a Temperature Controller (like this - https://amzn.to/2Fi9Fgj ), set to Heating Mode;
The relay output then went to the relevant wire in the Heater Controller loom that would tell it to turn on or off (on this particular heater controller, there was a specific wire that would allow this. The other more advanced controllers did not have that feature).

Something else I did in this setup but don't think you would need to bother with is fit a 3-way switch so the Remote Garage Opener could be bypassed when in the van. Essentially you have the secondary on/off controller with the yellow wire to turn on and off instead.
Question - applying and removing 12V to the yellow wire ... does this do a normal startup and - more importantly - a normal shutdown of the heater? You will know this already I am sure, but it is important that when the heater is turned off, it is able to go through the full shutdown routine as if all power is removed, it can both overheat and choke up - neither good over time.


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Yes, the yellow wire is just call for heat from the 801 to the d2, so the d2 still does all the pre heat and post heat cooldown cycle as normal, the d2 brain takes care of all of that.
Delighted with the eberspacher, it was a great find on a smashed waterboard van in the scrapyard.


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Eberspacher do make a controller that you can run remotely over the internet/gsm but it probably costs the earth

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