vanski
If it’s winter, I’m probably skiing..
Enabling full Fan (ATC) Airflow with Engine Off
Seeing folks talk about their Espars and getting them to work with the engine off has prompted me to upgrade the one final item I'm not super happy about with my heater booster engine off configuration: Having full air flow through the ATC (fan) compared to about 33% per the REST functionality.
I did a variation of Wiring Heater Booster to run from Switch but my 12v source is a house battery (most folks following this write-up run from the starter) and I routed everything SPDT relays without feeding 12v into any existing lines to light the line up (the write-up calls for splicing into existing wires). In the write-up there's a step where you feed 12v into an unused plug above the shifter. It's step 6 found at https://sprinter-source.com/forums/attachment.php?attachmentid=772&d=1169427461
Has this approached worked for me.. Absolutely, and on my ski trips I wake up to a toasty van with warm ski boots. BUT, the problem with this approach is that it essentially taps into the REST ATC functionality which only gives me three settings of air flow; low, medium, high. Most importantly the high is about 1/3 as high of air flow as you get when the vehicle ignition is on and you turn the ATC dial to high (4). I want 3/3. I want 100%. Am I being unreasonable?
I think I understand why Mercedes engineered it that way from the beginning; they wanted to limit the amperage draw folks were running so they didn't drain their starter battery.. Fine, I get it. But when I'm running my Espar for warmth I'm running from two 6v batteries (I might be going to 4 here shortly) in series which are completely disconnected from the starter battery and quite honestly it's not going to be the end of the world if I drain them. I haven't drained them yet....
So, I'd like to find the 100% power ATC line, route it through an SPDT relay, and have 100% ventilation capability.
Can anyone tell me where the ATC power line is that allows you to turn the fan on while the engine is running? Is there more than one wire for some reason? Has anyone worked through this or come across a write-up on this? I can't seem to find one.
As usual, thanks to all of those who contribute so much great information on this forum!
-Vanski
Seeing folks talk about their Espars and getting them to work with the engine off has prompted me to upgrade the one final item I'm not super happy about with my heater booster engine off configuration: Having full air flow through the ATC (fan) compared to about 33% per the REST functionality.
I did a variation of Wiring Heater Booster to run from Switch but my 12v source is a house battery (most folks following this write-up run from the starter) and I routed everything SPDT relays without feeding 12v into any existing lines to light the line up (the write-up calls for splicing into existing wires). In the write-up there's a step where you feed 12v into an unused plug above the shifter. It's step 6 found at https://sprinter-source.com/forums/attachment.php?attachmentid=772&d=1169427461
Has this approached worked for me.. Absolutely, and on my ski trips I wake up to a toasty van with warm ski boots. BUT, the problem with this approach is that it essentially taps into the REST ATC functionality which only gives me three settings of air flow; low, medium, high. Most importantly the high is about 1/3 as high of air flow as you get when the vehicle ignition is on and you turn the ATC dial to high (4). I want 3/3. I want 100%. Am I being unreasonable?
I think I understand why Mercedes engineered it that way from the beginning; they wanted to limit the amperage draw folks were running so they didn't drain their starter battery.. Fine, I get it. But when I'm running my Espar for warmth I'm running from two 6v batteries (I might be going to 4 here shortly) in series which are completely disconnected from the starter battery and quite honestly it's not going to be the end of the world if I drain them. I haven't drained them yet....
So, I'd like to find the 100% power ATC line, route it through an SPDT relay, and have 100% ventilation capability.
Can anyone tell me where the ATC power line is that allows you to turn the fan on while the engine is running? Is there more than one wire for some reason? Has anyone worked through this or come across a write-up on this? I can't seem to find one.
As usual, thanks to all of those who contribute so much great information on this forum!
-Vanski
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