Any one know how to run Espar heater off the auxiliary battery?

The Espar has a 25 amp fuse and runs it's little blower. It is a consumer. But you are right the fan and water pump can be put on the aux as well. Those lines are under the steering wheel. I forget which ones, but I posted it years ago.

gotcha.. the 25 amp fuse is mostly for the initial glow plug in the heater.. yes, the little fan requires between 1 and 2 amps depending on how fast its running.

I just wanted to make sure folks understand you want to route all components power consumption from house battery if your goal is to not draw down the the vehicle battery.

vanski said:

on my engine off espar system I simply ran properly gauged wire from my house bank to a fuse box which then runs the various components for the espar, atc, and auxiliary water pump. When I hit the switch my relays click over sourcing all power through the fusebox which is coming from my house bank compared to the oem circuit wiring

Good call on doing this... the system can draw close to 25 amps when the atc is in high and the system is ramping up (espar glow pins, the fan, etc) and if you really are going to use it as a heater it will drain the battery down if used for an extended period of time.

Click to expand...

Hey Vanski,

Can you give me a run down on how you did this please?

I also have the 7 day timer.

Do I just run a positive to the fuse box for the espar

A seperate one to the 7 day timer

And another the the Aux blower in the back?

Sure. I have a not so good, but functional wiring diagram I’ll post up when I get the chance, but the thousand foot level is using single pole double throw (spdt) relays to separate out all the circuits; t15, d+, heater power (forget what the wiring diagrams call this), aux coolant pump, interior hvac blower motor (some people activate the rest circuit which activates both the blower and aux water pump but I like going directly to these circuits), rear blower motor (for you), rear aux coolant pump (I think your system has this, correct????), etc (am I forgetting anything?). All of the oem wiring will be hooked into the normally closed configuration of the relays. Your 7dt will be the signal wire to a bus bar which will activate all the relays. I have also used simple 12v thermostats to also activate/deactivate the relays by sending 12v to that buss (although this isn’t he best way to do it because then you’re sending 12v back to the 7dt, but I’ve never had a problem.). So when either the 7dt, or whatever ‘switch’ is used, you are then running all power from the house bank (via properly fused AND properly gauged wires.

So to recap:

+ oem circuitry stays as is but runs through the normally closed contacts of spdt relays... all power comes from starter battery
+ when the switch is flipped via 7dt or thermostat or whatever, the relay coils are activated, and all power comes from the house bank

So that’s really it... implementing it of course takes some time. I still can’t do this project in under 10 hours and I’ve done it several times. But the results are worth it imo, especially for you having that rear heat exchanger.. jealous!!!

I’ll post my crude wiring diagram (which won’t have your rear heat exchanger info) when i get a chance.

Okay. Attached is a crude wiring diagram which has some errors (i cant correct it because I was using a trial version of the software and the trial expired long ago) and honestly Im really not proud of it but it will give you an idea on how to go about this project.

Notes:

+ The purple lines represent the OEM circuitry from the starter battery. So you would cut the wires on the signal side of the wire, not the component side, which then goes to the normally closed, pin 87a, on the relay.
+ The red lines represent the fused house battery side. So when you activate the relays via the 7dt, a 12v thermostat relay, whatever, all power will be sourced from the house battery and not the starter battery.
+ There should be a purple line from the harness to the Terminal 30 (primary espar power line) to pin 87A
+ Specific to your configuration you have a second plug on your Espar. This wire goes to the REST circuit on the back of the ATC (HVAC control panel) unit. So you only need to intercept this wire to activate the ATC
+ My key fuses are off.. terminal 15 and d+ dynamo really only need to be like 3 amps. Wires can be gauged accordingly. There are other errors.
+ Of course you will need to put in relays for the additional components per your configuration; rear heat exchanger fan and i believe rear aux coolant pump..

Understood this isn't perfect, but it should get you heading in the right direction....