Webasto external temp sensor

Submitted: Thursday, Aug 06, 2015 at 13:26
ThreadID: 129882 Views:4693 Replies:5 FollowUps:8
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Hi all,

Does anyone own a Webasto that has an external temp sensor fitted?

I have always wondered why our Webasto won't run flat out when on high temp setting, it continually fires up for a short while then only blows cooler air .. A while later it's pumping hot air fine again.

It points to me to be a thermostat issue and upon reading the Webasto online manual there is mention about the external sensor. I'm doubting mine has one fitted as there is a plug exiting the Webasto that is not connected to anything and it looks to be the same connection the sensor uses.

Before I order the part it would be good to know if I'm on the right track. Any help given much appreciated.


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Mick & Vickie

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Reply By: Turist - Thursday, Aug 06, 2015 at 16:36

Thursday, Aug 06, 2015 at 16:36
Mick the standard sensor is located in the input throat of the Webasto.
Bushtracker installed some with the cool air intake close to the hot air duct, result is that the heater sucks in hot air and turns down the power.
Worth checking the duct locations first.

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Bob
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Follow Up By: NIK `N` OFF - Friday, Aug 07, 2015 at 08:59

Friday, Aug 07, 2015 at 08:59
Thanks Bob, I've been on the phone to Webasto who put me in contact with their service agent here in the West, they were very helpful and told me that the plug I was looking at was for diagnostic purposes and not for an external sensor. They also asked about the positions of the inlet vent. I don't think the positioning is the problem, they are both fitted along the back wall approx 1.5mtr apart, not facing each other plus we had the door and window open.

With the help of a mate I will remove it on Monday and take it in and have it bench tested. If it tests out ok then I will look at changing the inlet position.

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Reply By: Flavs - Friday, Aug 07, 2015 at 12:48

Friday, Aug 07, 2015 at 12:48
Hi Mick
You may have to do a service on it Mick.
In the BOG Bible there is a PDF on Decoking created by Bob. It is quite easily done following the instructions and pictures (for you! lol). The flame detector ("S" model) may need replacing. If you do the service you would be best doing all the parts (see Bob's PDF for the list).

Good luck
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Noel
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Follow Up By: NIK `N` OFF - Friday, Aug 07, 2015 at 13:03

Friday, Aug 07, 2015 at 13:03
Noel, Is the BOG Bible accessible on this web site?
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Reply By: Flavs - Friday, Aug 07, 2015 at 14:07

Friday, Aug 07, 2015 at 14:07
Hi Mick,
The BOG Bible is not yet accessible, but will be.

I have emailed you the PDF

and posted the file here


Hope this helps
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Noel
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Reply By: Col & Diane - Friday, Aug 07, 2015 at 23:16

Friday, Aug 07, 2015 at 23:16
G'day Mick,
Just as a matter of interest I have just done a service on mine (Air Top 2000ST) and the cost of the bits from CRS in Brisbane were:
Burner Cartridge: $88.00; Glow Plug: $95.00; Gasket Set: $16.00; Fuel Filter: $19.00; Air Intake Silencer: $20.00. (All GST inclusive)

My model is a little different than the one in BOG Bible article which was very useful. (thanks Bob for putting in the effort to produce that article) The Service Manual available online also has detailed descriptions of the repair procedures (although the bloke in the white shirt doesn't get a mention).

I don't understand the reference by others here to a sensor in the input to the Webasto. (Maybe earlier models). On my model the thermostat is in ON/OFF control switch. The external temperature sensor that you mention actually plugs into the control unit, and is used if the main control unit is unable to be placed in the area that is usually occupied.

The unused connector coming from the loom at the main unit can be used to connect a CO2 sensor according to the Service Manual.

Sorry that I can't help with your specific problem, but hope some of this is of use.

Col
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Follow Up By: NIK `N` OFF - Sunday, Aug 09, 2015 at 17:14

Sunday, Aug 09, 2015 at 17:14
Thanks Col, every bit of info is a help. I will with the help of a mate remove the Webasto tomorrow, I will probably take it to the service agent and have them bench test it 1st, hopefully it exhibits the same as it's been doing.

We just spent two nights in the van in freezing conditions, car and van covered in ice in the morning. The Webasto barely warmed the van, it continually fired up for a short while then went into a cool period before firing up again.
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Follow Up By: Turist - Monday, Aug 10, 2015 at 16:06

Monday, Aug 10, 2015 at 16:06
Confusing info Col.
Below is an extract from the Webasto manual.
The external sensor is an option not normally fitted to caravans due to the "open space" uncluttered design that does not inhibit air flow.
The conventional rotary selection switch is a selector only, it does not contain a temp sensor.
Your installation has me puzzled.
There is further reference to the purpose of having the temp sensor on the return air side in the FAQ section of Webasto's web page.

Regards
Bob

During operation the combustion exhaust gasses flowthrough the heat exchanger charging its walls with com-bustion heat, which in turn is taken up by the heating airdelivered by the heating air fan to be routed to the ve-hicle interior.The temperature of the heating air sucked in ismeasured by means of a temperature sensor fitted tothe air intake side of the air heater or by means of an ex-ternally located temperature sensor.A temperature below the one set with the control ele-ment increases the heater performance up to maximumheat. In order to extend the burner idle period of Dieseloperated heaters during permanent operation with aheating performance in excess of 1.1 kW, the fuel dos-ing pump delivery rate is reduced every 15 minutes for20 seconds.
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Follow Up By: NIK `N` OFF - Monday, Aug 10, 2015 at 17:48

Monday, Aug 10, 2015 at 17:48
Ok, I took my Webasto to the service agent this morning and it was bench tested. I was shown the computer program testing my unit and the technician is convinced it's the ecu is the problem. It was producing over exaggerated figures of usage around 2000 hours and upon running the Webasto it gave the same problems I have been having with it.



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Follow Up By: NIK `N` OFF - Monday, Aug 10, 2015 at 17:54

Monday, Aug 10, 2015 at 17:54
I pushed submit before attaching the 2nd photo. They are of the heat sensor, it is clipped to the side of the body and has the blue wire going to it.
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Follow Up By: Col & Diane - Monday, Aug 10, 2015 at 21:19

Monday, Aug 10, 2015 at 21:19
Confusion indeed! Maybe due to us discussing different models of Webasto heaters. That photo of yours Mick looks (I think) the same as mine, an Air Top 2000ST. That sensor is indeed a heat sensor, but an overheat sensor. If for example you block the air inlet, the machine will overheat, the sensor will detect it and turn the machine off. It is not involved in controlling the temperature during normal operation.


Bob, I'm not disputing what you say but we need to state what models we're discussing. Mine was fitted in 2008, and is an AirTop 2000ST.

This is what my controller looks like:


As you can see it is not just an ON/OFF switch.

In our van the controller is situated near the east-west bed at the front of the van. When not in bed we block this area off with a curtain, which is not ideal because the thermostat (in the controller) is effectively outside the area where we are sitting. Thus I intend to fit an external temperature control, which will be in our living area. This external control attaches to the main controller and then effectively become the thermostat.


This is what I was looking into when Mick submitted his post. It has only taken me 7 years to get around to it.

I hope this clears up any confusion. If not, I'm happy to be proved wrong. (It wouldn't be the first time).

Col
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Follow Up By: NIK `N` OFF - Monday, Aug 10, 2015 at 22:51

Monday, Aug 10, 2015 at 22:51
Col, I'm not exactly sure if it's a heat overload sensor or temperature limiting sensor, from what the Tech said I'm guessing the latter. He did disconnect it when testing my Webasto.

My Webasto is the Airtop 2000ST which looks a different model to Bobs PDF file
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Reply By: NIK `N` OFF - Tuesday, Sep 01, 2015 at 17:45

Tuesday, Sep 01, 2015 at 17:45
A follow up on my Webasto,

After initially thinking the problem lay with not having an external temp sensor I decided to have the unit bench tested whilst plugged into the diagnostic plug. It turns out the problem was the ECU, I had the Webasto agent Care-A-Van in Canningvale WA order in the part and fit it and retest the heater. Everything worked and pleased to say the Webasto is working perfectly, blasting out the heat we have never felt before. I'd go as far as to say we had the dodgy ECU problem from new because it never blew hot air longer than 10 minutes, I wish I had of picked up on this whilst if was still under warranty as it was a $710 repair bill. $400 was the cost of the ECU the rest labour and freight.
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