Webasto Airtop 2000s Problems

S

SB24Svn

New Member
Hi,

I last turned on this heater (12v diesel) a year ago where it was working perfectly. However testing it today it's just blowing cold air.

The first time it was started up today the heater blew cold air and turned off after a few seconds, with error code f07. Realising this was the pump I disconnected the lead to the pump and reconnected it which seemed to fix it (I don't think I'd pushed it all the way in). The next few times the heater started up and stayed on with a good strong output of cold air, but I constantly got error f03. I checked the voltage from the heater and then at the fuse box and both showed 13.69v. Mostly the heater does stay on for a few minutes but then turns off on its own - however sometimes it starts and turns off after only a few seconds. Over the course of trying a few more times I got error f08 followed by f01, which seemed random. Then back to f03 which is the most consistent, but the voltage is fine.

One thing is I don't believe fuel is getting into the heater. However there is no blockage in the pipes (I have confirmed this), and the pump seems to be working fine (I also have a replacement pump which I've tried with no difference) - it clicks and when the output of the pump is disconnected the fuel is shooting out. With the pipe disconnected at the heater end (with heater switched on) fuel does not shoot out (should it?). Sometimes the pump stops clicking after a few seconds and other times it stays on.

One thing is the burner is never starting up. Why would this be? Because of the lack of fuel entering the heater?

Can anyone please offer any advice on what I can do as I am a bit lost?

Simon
 
Try priming the hose and pump as some facet pumps don’t like lifting fuel from dry
 
Has it been submerged?
maybe the nozzle is blocked?
 
Why has the heater not been run monthly as per the instructions in the manual? This is the main cause of failure!
Ignore the fact that the fuel pump is not working to begin with.
Common problem that people blame the fuel pump just because the fuel pump does not actuate - this is what it is supposed to do otherwise you will fill up the heat exchanger with fuel and risk an explosion or a stream of fire running out of the exhaust. The fuel pump will not start until the start up checks have all passed as OK.
F08 fan error could be brushes are worn out or it is shorted causing the voltage drop that is reported - what age is the heater? (year before the earliest date of the 3 on the label).
If there is a single error in the checks start up will fail. Do the voltage check at the heater plug to the ecu whilst the heater is trying to start.
Time the heater error using figure 502 in the workshop manual, this can aid diagnosis of the actual error.
 
Thanks for the response, it's appreciated. The date is 2005, which makes sense as the van is 2006. However it was a government vehicle and the heater has had regular services right up until the van was sold (2016) so it's in great condition (as far as I can see).

Had another go today. Every time it showed error f03 with no other errors showing. Took voltage at the ecu which before startup was 13.6. As soon as I turned heater on it dropped to 8.7 (varied each time between 8.7-9.8), and after about 17 seconds it then jumps from about 10.2 upto 13.6, then at 28 seconds shows error f03. It remains on 13.6 until 2 minutes 20 where the heater turns off.

I've double checked all connections and they are all perfect. I have no idea what could be causing this error. The pump was at least clicking yesterday but wasn't today at all. I'm really lost on what to do.
 
If the supply voltage to the heater drops to 8.7v then you have a power delivery problem, not necessarily a heater problem.
Unless I have misunderstood what you are measuring.

Pete
 
Have you checked earthing points, not teaching anyone to suck eggs but make sure you have no high resistances don't rely just on voltage don't forget you can have voltage and next to no current, check all connections
 
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As above, especially the earths which do tend to get overlooked in tracing faults,
but I would be concerned at the earlier fan error. The heater is now 15 years old so I personally would strip it as a matter of course and take a look at the brushes. They are not the easiest to work on though - not for the faint hearted, not as easy as a big domestic mains motor. There is also a more unlikely possibility that the glow pin has shorted leading to the voltage drop. The voltage should only drop to around 11v briefly when the glow pin is switched on rising to 12v/12.2v as the power is dropped so there is certainly a problem in that area. Ideally it needs the ecu read to see what other errors are stored.
Ignore the pump - that doesn't come into play until the checks are all passed first.
 
To give an update on this:

We re wired all the earth connections (even though they all seemed solid) which did get rid of the F03 and fixed the low voltage. We was then getting the no fuel error code even though we could hear the pump clicking and pumping fuel. To fix this we primed the hose, and after connecting again, the heater worked perfectly! Can't thank you guys enough for this advice!

However, after turning it on today (giving it its monthly run), the heater only got lukewarm and didn't seem to be blowing as fast as it did before. For a brief, brief moment the heater got too hot to touch, but then straight away when cold, then back to lukewarm again. I can hear the glow pin start up and everything seems to be working. Any idea what the issue may be? On one of the tries we got an F06 but on every other switch on no error codes were showing (even after running it for 10 minutes).

The only thing that has changed since it was working is screws have gone into the baseplate.

Any help appreciated guys
 
Hit and miss starting like that is usually the burner pad is clogged with carbon and needs changing. Any smoke on start up? Time for a strip down and service methinks ( I wouldn't count on a heater in a Gov vehicle being serviced regularly and correctly, you should see the state of some of the heaters that have come out of scrapped ambulances).
 
On the one occasion I got an F06 there was lots of smoke on startup. On other times none. Could it be the internal temperature sensor thinking its hot enough so its just sending out lukewarm air? Is there anyway I can bypass the sensor? (reading your posts on another thread I'm assuming its pins 8 and 9 on the controller)?
 
You say that this heater is a 2000S so instructions for a 2000ST do not apply as it is a completely different heater.
You are grasping at straws here! If you are satisfied that the voltage is remaining stable now during start up it is time to think of a service. That is the first thing to do with a heater that you do not know the service history of at all. To get an F06 is extremely unusual - the sensor is very reliable. I think that I have replaced only 2 in the last 15 years and one of those was physically damaged.
 
All great advice, thank you. So I took it all apart today to give it a good clean, I have to say it all looked pretty good (comparing it to the one on the guide I was following) - I barely needed to do anything apart from removing a tiny bit of carbon from the burner pad. It does have a service sticker on it for 2016 and it hasn't really been used since then so I guess if it was serviced properly that would make sense. One thing I was unsure about was the little wires on the bottom of the burner pad, is this normal? (I've attached a pic of the condition).

Started it all back up and it's exactly same, no errors and everything seems to work correctly with the glow pin starting up and fuel being burnt, but it only gets warm and it doesn't seem to be pushing the same amount of air out of the vent as it did before. The heater itself is boiling hot though you can barely touch it along with the exhaust pipe. Have you any more ideas of what it could be please or anything I could try for this type of fault?

Just a side question if I may with you saying instructions for the 2000st won't work on the 2000s, does that mean if I were to add an external sensor (which I was looking at doing anyway) I couldn't attach it to pins 8 & 9 on the controller? Is it a different process?

Thanks again for all of your help, it really is appreciated.

burnerpad.jpg
 
That burner pad is due for replacement, when you get it out you will find that the back of it has glazed black carbon across it going by the evidence of carbon building up to the side of the burner tube. For the sake of £4 change it. If you don't want to strip the burner tube and the pad holder you can get a Chinese replacement set for around £15 which are good enough but do not permit subsequent replacement of the burner pad alone due to welding being used to hold the burner pad holder in place.
New one
IMG_1631 (Copy).JPG

If you are not getting full throughput of air is there a blockage in the ducting or a closeable vent being used instead of a fixed one? Kid's sweet wrappers and fluff can build up behind the vent.

See my reply here regarding external temp sensor on a 2000S Webasto AT 2000 - Temperature Sensor? How Does It Work (as In Setup With Controller Etc)
 
Ok so bit of an update:

Replaced the burner pad, replaced the gaskets, fired it up and it worked perfectly. It got hot and stayed hot. The air is being pushed through normally after I found a gap in one of the joints in the ducting. What a relief!

However, after turning the heater off, half way through the shutdown phase, the fuse blew (10a fuse). Now, as soon as I turn the heater on the fuse blows instantly. I tried it with a 15amp fuse and the heater turns on but doesn't fire up, and checking my meter shows its pulling 31 amps! What has happened here? It's just one thing after another :(

I can't thank you enough for your help though as I'd be lost without it. I do hope you can help with this latest issue. Thanks.
 
With those amps you are looking at a direct short of the glow pin or motor, my money would be on glow pin as that is where you were working.
Check that you don't have one of the wires at the top of the glow pin positioned too close to the metal especially when inserting the holder into the burner tube. The indentation should prevent that but if the glow pin isn't inserted fully and at the correct orientation it can make contact.
Hopefully there is no damage to the ecu if this has occurred.
 
Last edited:
Ok it made sense that the glow pin would be touching the metal as I remember it feeling a tad restricted when I was putting the heater back together, thank you for suggesting that! So I took it apart, took out the glow pin and put it back in making sure it was pushed in fully. The heater went back together a lot easier so I knew it was fixed. Sure enough fired it up and amps were back to normal and it heated up and stayed hot for 20 minutes.

On a side note one issue I've always had is I've never been able to turn it off - I press the button on the controller and the fan does start to decelerate, and just as you think it's going to turn off, it fires back up again full blast, any ideas why this would be? I always just have to remove the fuse to turn it off, eventually I'll just install a switch if it carries on if I can't force the shutdown.

So after turning it off, I tried turning it on again. Within seconds got an F04. Strange. Tried again and the air sounded like it was chugging, with a F09 error showing. The amps were still normal. Every consecutive try since shows error F09. I took out the two plugs on top of the heater and put them back in again to see if that would reset anything, and now I get the F09 and chugging but the amps are back high into the 20s again (shows 25amps). It seems every time I fix something, a new error appears :( Is it still something to do with the glow pin, should I replace it?
 
The f04 would be because you interrupted the shutdown = you MUST NOT shut the heater down by pulling the power from it. It has to cool down properly otherwise the heat exchanger will overheat which can lead to overheat protection activating, heat exchanger warping, case melting etc. (It can take 8 to 10 minutes for the heater to shut off fully after switch off) It looks like you are bringing problems down on your own head here.
Have you not read the relevant manuals for the heater?
 
That's fair enough, I have read the user manual but admit to not seeing it took that long to shut down - what you say makes total sense.

I tried it again having cooled down and the amps have gone down to normal levels but I'm just getting revving/chugging of air for 3 seconds before the heater switches off and shows error F09. Is a new glow plug needed then? If so what could have caused that (because it's only since taking it apart this error has shown)?

Really appreciate all of your help
 
It could be the glow pin that is in error but equally it may well be the ecu has been fried with 30+ amps going through the glow pin circuits. The glow pin wire is correctly routed under the clamp and not free to chafe on the casing and/or rotating impeller? New glow pin is around £16 from ebay, Chinese ones are fine.
New ecu would be in the region of £220 - £250 if it came to that.
Glow pin resistance should be in this range:

6.3.1 Glow Plug Resistance Test
During electrical testing of the glow plug using a digital
multimeter, the following readings should be obtained:
Glow plug 12 Volt (red)
Resistance at 25 °C: 0.324 ... 0.360
Test current: < 5 mA

Ideally you need a 4 wire meter to read the resistances accurately.
 
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