Auxillary Heater problem

[Christer]

I have a Mazda 2007 that has an factory incorporated Webasto Engine heater (Webasto Thermo Top C is the model).

My problem is when I have the heater fuse connected, the heater blower start working when I park and lock the car.
It starts and stops at random and drains the battery.

I get the following DTC: B2454 Blower fan circuit open ( CPU detects Malfunction in blower fan circuit )

Anyone have any tips or tricks to resolve this? Some say the Control Board inside the Webasto may be the issue, still I see alot of theese problems with this car. Seems weird that the same issue happens to so many.

And the issue with the short circuit malfunction in the heater that triggers only due to activating the door locking mechanism.

Topic

[Vince]

Oh I worked on this exact model of heater at school very recently! 😛

Maybe the ECM detects the actual operation of the thermostat. I would guess the heater wasn’t part of the OEM equipment. Otherwise it sound like the normal operation of the device. They do use quite a bit of power (around 42W if I remember). The trucks that have one of those often have dedicated batteries with a disconnect to separate them from the other batteries when the heater is operating and reconnect them to the alternator to be recharged.

I can try to get my hands on the installation manual I had when I made the wiring for the heater I installed on a water tub (for EGR cooler leak tests). It was the exact model you mentioned, the Thermo Top C, but diesel instead of gas). I saw the manual still laying around last Friday.

Although I’m not sure how unit is supposed to operate in that particular application. Is there a timer control? I know there’s an optional timer that you can install.

EDIT: I was able to locate a PDF version of the installation manual right here: http://www.techwebasto.com/redirect/heater_main/907512.pdf

Should you attempt any troubleshooting, this will probably give you a place to start 😛

[Christer]

Yes, there is a timer control like the one in the picture.
The car is also Diesel and the heater runs on Diesel.

Would be nice to understand why the open door or door locks triggers the blower motor inside the heater though.
Could it be related to the BCM (Body Control Module)? I have another issue with the doors, there is a two cabled plug I pulled out from the actuator on the driver-side because the doors went crazy with the locking mechanism. And pulling that cable fixed my issue, think it is a double locking system or something, not sure.

I am looking for a used replacement BCM or Webasto device, in the meantime I will try to narrow it down by doing some testing with a multi-meter on the door lock timer unit, actuator and wiring harness to see if there is continuity and measure the resistance (ohm level).

I really hate those electronic bugs, I am not that good with wiring diagrams. :unsure:

Attachments:

• mini-timer-1533-webasto.jpg

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