Current Draw - Instrument Cluster & Front Heater Blower

The past day I've been trying to figure out why my battery keeps dying. Step one complete, but now not sure where to go next. I might get told to use the search for this, but I'm not quite sure what to search for here on the forum.

Here is what I have found. It appears the current draw is coming from the Front Heater Blower and the Instrument Cluster... Any ideas from all you T1N vets?

Combined draw: .281amps

Front Heater Blower (Block1- Fuse21) Removed: .158amps

Instrument Cluster (Block 2 - Fuse6) Removed: .008amps

I'm sifting through the wiring diagrams now to try and make sense of it all. I'm no mechanic or electrician... could take a while. Any help is greatly appreciated!
I should probably add that the vehicle had an aftermarket security/keyless entry installed. This has since been "removed" but there remains some wiring under the dash. Will investigate what is connected down there tomorrow. Thats my first suspect for the instrument cluster draw. No ideas for the Front heater blower

Here is what i traced down with the wiring diagram.

Battery -> Block 1 -> Fuse 21(front heater blower) -> Automatic Temperature Control Module

-> Heater Timer Aux
-> Blow Motor Resistor Block
-> G203

Battery -> Block 2 -> Fuse 6 -> Instrument Cluster

-> Data link connector
-> Airbag control module
-> Fuel Level Sensor
-> Parking Brake Switch
-> Brake fluid level Switch
Last edited:


Erratic Member
Is the front fan actually blowing? (i suspect not, since that should take more power)
Perhaps the REST button is stuck "on" in some way?

Somewhere buried deep in Sprinter documentation is that the "idle" load on the Sprinter should be about 35 to 50 milliamps.
0.035 to 0.050 by your numbering.

Note that the instrument panel "wakes up" when you open the door, and doesn't drop to low current again until after a couple of minutes have passed.
If you have Remote Key Entry, there's going to be some (small) amount of current going there, too. (so it can listen).

The heater timer will draw a tiny amount, too (of course), but if the display has blanked it should be below 20 milliamps (i'd guess)

good luck
p.s. i just read mine, and i'm seeing 0.020 to 0.030 (i removed my 7-day timer when it died a year ago)
On another Sprinter that dropped by for DAD-sniffing, their "idle" current was 1.25 ... and he was also complaining about battery-dying problems.
Last edited:
Thanks Dick. I'll have to do some more readings tomorrow and will be sure to keep the door closed several minutes before taking them. Do you happen to know if all 4 doors have sensors that wake up the instrument cluster?

As for the front fan - it is not actually blowing. For testing the actual REST button, would I do this by removing the HVAC face and checking to see if there is current coming from the switch?


Erratic Member
Note that i've updated my message's footnote. Mine reads 0.02 amps on my meter.
The other visiting Sprinter was 1.25 amps (i had misplaced the decimal point during my first posting)

Only the front doors light up the Instrument Panel ... but opening any door will start the dash door lock button's red triangles running.

For testing the REST, i'd simply attach the meter, unplug the blower resistor, and then go push it.
That will start the fan (high draw), but if you can unplug the blower resistor (in engine compartment near cabin air inlet) that should take the fan itself out of the running.
There will still be one relay in the game (unplugging the 7 day timer should kill *that*), and that relay itself could be the draw. The service manuals give two possible blower/resistor arrangements:


How the blower motor figures into it:


The blower motor resistor block:


Last edited:


Active member
Here's another data point of quiescent current for chassis battery.

After the door timer settles out and dash lights go out, I measure 37 mA for my '06 3500 Winnebago MH.

I've isolated these currents:

Espar heater (fuse #1): 7 ma
Instrument panel (fuse #3): 5 mA
MH step controller: 22 mA
Unaccounted: 3 mA

Without the MH Kwikee step controller, chassis battery quiescent current is 15 mA.

Top Bottom