Vehicle & Technical > Discovery

Webasto Pre Heater & Alarm sensors.

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Andy.:
Sometimes when I run my pre heater the alarm is activated by the blower once in operation. It seems to trigger off the overhead sensors by the blower.

I have the blower set to speed 2 as this is the best option.

I have seen this "Alarms, it maybe necessary to isolate the ultrasonics of the alarm, depending on type fitted. This generally involves using a change over relay to break the ultrasonic connection. The trigger wire to the relay can be taken from the fan relay signal. Use same type relay".

How do I go about wiring a relay in

Matt_H:
you'd need to work out if you can cut the feed to the sensor without setting the alarm off first.  

If you can and you can work out which one to cut (note you'll need to cut it from all sensors unless there is one main ultrasonic connector on the alram control) then you need a change over relay

you can find a 5 blade changeover here

http://www.vehicle-wiring-products.co.uk/VWPweb2000/relays/relays.html

using the diagram to go by wire the connectors as follows

30 sensor feed
85 fan + when running
86 ground
87 nothing (unless you want a nice warning light)
87a other side of sensor feed where cut

Paul:
Andy,

Try this... Cover the interior sensors with insulation tape so that they
can't see anything, Set the webasto to come on in say 5 mins and
lock it up using the alarm.

Doing this will tell you if the alarm is sencing the air movment in the
vehicle or the voltage drop when the heater motor starts up.

Andy.:
Cheers Paul will give it a go.

Andy.:

--- Quote from: "Matt_H" ---you'd need to work out if you can cut the feed to the sensor without setting the alarm off first.
--- End quote ---

How can I tell this  :?:  


--- Quote from: "Matt_H" ---If you can and you can work out which one to cut (note you'll need to cut it from all sensors unless there is one main ultrasonic connector on the alram control) then you need a change over relay
--- End quote ---

According to the work shop manual, there is one main ultrasonic sensor module connected to the alarm ECU.
The rest of the alarm is made up of a bonnet switch, door switches, the lock barrel and sill buttons.

If I can cut the feed :?: there are two sensor wires going to the ECU so these can be wired to the relay unit  :?:

There is a connection in the work shop manual wiring diagram for a Fuel burning heater unit to the ECU to I presume LR pre thought of this problem  :?:

And where is this ECU the manual has it down situated in the steering column is this correct  :?:

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