View Full Version : Aux Heater Clicking, No Heat Output

03-06-2013, 04:30 PM
First, I am unsure exactly which aux heater I am dealing with. I have a 2004 118WB Passenger Van, that was a Costar research van set up as a mobile office. When I turn on the Aux heater from the 7 day timer, everything works as it should, except I don't get any heat. I do hear a clicking noise, that seems to get faster and faster, until it stops for a few minutes and then repeats the process. I'm sure this has been answered before, but a search turned up nothing, so if anyone can point me in the correct direction that will be greatly appreciated.

Bonus points if anyone can suggest why my front switches are not working with exception of door locks (front and rear window defroster and ASR off switch) Could this just be a fuse?


03-06-2013, 05:00 PM
The clicking is the fuel dosing pump working as it should. I would have thought you would hear the fan for the combustion air too since I'm sure the heaters onboard controller won't pump fuel unless it knows it has air. You should also hear the coolant pump.
Basically what you are hearing is the pre-programmed 2 attempts to start, when it fails to start after 2 attempt the ECU shuts it down.

Espar's website has a download section with loads of troubleshooting guides, yours is most likely a version of the D5W, I think its D5WZ in mercedes vans.

The unit has a flame sensor and an overheat sensor (or combined flame and overheat) so knows when it hasn't started or if it is overheating because the coolant pump is not running, it can also record fault codes like a modern car to allow a dealer to diagnose the problem, but most likely you have a blockage in either the air inlet or exhaust pipes, that seems to be listed as the most common cause for the double start failure and nees no dealer intervention....
The troubleshooting guides list several other checks you can do before taking it to a dealer.

03-06-2013, 05:02 PM
It's failing to fire up, so it stops trying for a few minutes and then tries again.
Could be glow plug failure, furnace fan failure, or lack of fuel flow (do you smell diesel in the driver's front wheel well)

It'll take me a while to look up what fuse might be common to the items you list... perhaps the Aux Heater is among them...


Boz Staggs
03-06-2013, 06:34 PM
My guess is a bad coolant pump based on my own experience with the same symptoms.

03-06-2013, 08:36 PM
Welllll... there is a common fuse for the defoggers and ASR switch (and hot water circulating pumps, so it could be the heater problem, too).
According to the schematic, it's Fuse Block 2, fuse 1 (10 amps)
But Fuse Block 2 is the one beside the driver's seat, so *your* position/size may/will differ.
On my 2005, it's actually a 15 amp fuse at position 7, labeled as "horn/air recirc solenoid valve/rear wind heater/optional equip 15"

Here's the 2004 service manual's take on what's hanging on that one circuit (does your radio work?):


But it could also be Fuse 7 in Fuse Block 1 (under the steering wheel), or fuse 20 (circ pumps)
Or the failure of the Optional Equipment Relay underneath the driver's seat.


03-06-2013, 10:36 PM
Thanks for the info. Radio does work, but this van has so much aftermarket wiring wouldn't surprise me if it was on a different fuse. I don't have rear defroster either, so the fuse box is where I will start. I was under the assumption that if it wasn't firing up, the fan would shut off automatically. Will post what I find.

03-07-2013, 03:07 AM
Ok, found the fuse box on the side of the seat. Looks like rear defroster is a relay, and I doubt thats gone bad? As for the aux heat, fuse is good. Located it under the battery and watched it try to fire up. I can smell fuel, and I'm guessing it's an air problem. When it tries to light, some smoke comes out almost like a backdraft. Doesn't seem to successfully fire. Any suggestions for cleaning out the air lines? Where does the exhaust line go? Thanks for the help

03-07-2013, 03:26 AM
This post suggests that it may be the coolant pump. Thoughts?


Boz Staggs
03-07-2013, 04:32 AM
Just to reiterate, mine had the exact same symptoms. The coolant pump was not working. It's a known problem part.

03-07-2013, 04:51 AM
I'll try a new pump, thanks for the help