Technical Heater Fan on Full, won't turn off.

[DucatoAmb]

Hi everybody.

Got an issue with the works Ducato that I hope somebody can assist with.

Apart from this annoying issue it has been a reliable workhorse.

Its a 2016 ex NHS Ambulance, manual gearbox, Euro 6 without AdBlue with Climate Control rather than just AC

The issue is the fan is stuck on full, you can't turn it down or turn it off, even turning the HVAC unit "off" does nothing, the fan still keeps going on full blast.

Has anybody else had this issue?

Did a code scan and got a random trouble code that gave no results on Google.

:B191912 Cabin Fan (SC to VBatt) circuit short to battery"

I was thinking an internal fault inside the Climate Control Unit on the dash.

Any hints or advice welcome before I start to strip the dash?

Can find the part used for just over £100 on the Bay or E, so not the end of the world

Thanks

 

[the green vanper]

Hello,

I wouldn't say the error code is random. I'd say at least it's related...

Find the fuse / relay and take each of them out, one at the same time. It should stop.

Relays like to get shorted... You could also put another relay with same parameters in the place of the original one. That could help you to exclude the relay itself from the possible causes list.

The x250 and x290 Ducatos electronic modules like to get wet through the system that (should) evacuates water from the windshield.

 

[Communicator]

The following are my thoughts only, and not based on actual experience of the problem. My PVC is an x244 and does not have a BCM.

I do not think that the BCM can monitor the fan curent, as it can only "see" what is directly connected to it, which is the relay coil, So how could the BCM detect welded contacts on a relay? Relays are rarely the prime cause, but the cabin fan is one of the larger loads controlled via a relay. As suggested, they are easy to eliminate by substitution.

If the relay is removed, the fan should not run, but the BCM may detect the missing relay, and report an open circuit, if the fan is switched ON.

I do not know what resources are available, but with the relay removed, can you test for 12V across the two smaller sockets (85 & 86). Is any leakage sufficient to operate the relay?

If @the green vanper 's very sensible comment about electronic modules getting wet is expanded to include the engine bay fusebox (B001), then we may have another possible cause. There have been several reported failures of this fusebox. Also there is the known problem where a wiring loom under the LH headlamp can abrade against a tubular frame member. but I do not have any info or the wire routing.

 

[koivula]

Hello, have you found a solution for this issue? I am experiencing the same problem at the moment…