Webasto on old T5 - what’s “normal”?

[laeli]

Hello everybody, I just got myself a second hand T5 (2007) and I’m puzzled by the Webasto aux heating. I have read all posts about the earth shunt issue, but before claiming I have a problem I would like to better understand what would be considered “normal operation” as I lack a reference. I would appreciate if someone with a good functioning heater could share some voltage values/drain of their equipment when operating for hours.
Mine starts with large battery drain (I understand that this is normal), runs for 6-7h and then turns off. Completely, no light on the symbol in the control unit, neither red nor yellow.
Last weekend I took a picture when it stopped, it showed 12.2V and 40%. Fuel was above half, so plenty of it.Problem is that with this % it won’t kick off again, when I tried, the battery dropped to 10% (I didn’t take a picture, I think voltage was showing 11.8V) and, after few moments of clicking sounds, the whole system switches off again. I need to start the engine, just 5-10 minutes running, then the battery is showing 100% and I can immediately restart the heater. Note I only keep level 1-2 when it runs as it is warm enough.
Is this its normal way of working? Just 6-7h of hot air, so less than a night sleep? Is it normal that it stops at 12.2V?

Second question: I watched during (seemingly) proper functioning, some time after starting it with engine on, and there’s always a constant consumption of around -4.2A. Nothing else is on, no fridge, no lights, nothing plugged. Why is that? I thought that after starting it should just run on diesel, not the battery. Is this due to the fan of the webasto? Is -4.2A a normal value? (Then no surprise the battery drops to insufficient level in 6-7h I guess....)

Any tips to get it running longer are appreciated. Anything else I should check? (note both leisure batteries were recently replaced, they’re not as old as the van!)

Thank you very much.
Elisa

 

[flying banana]

It burns diesel to produce heat. Everything else is electric . The fuel pump,the air fans, the glow plug etc. Once burning the glow plug switches off. That is the moment the current draw should drop. Maybe one of your leisure batteries has a blown fuse so your running on 1 battery? The heater should run longer than that on a low heat.

 

[WelshGas]

Hello everybody, I just got myself a second hand T5 (2007) and I’m puzzled by the Webasto aux heating. I have read all posts about the earth shunt issue, but before claiming I have a problem I would like to better understand what would be considered “normal operation” as I lack a reference. I would appreciate if someone with a good functioning heater could share some voltage values/drain of their equipment when operating for hours.
Mine starts with large battery drain (I understand that this is normal), runs for 6-7h and then turns off. Completely, no light on the symbol in the control unit, neither red nor yellow.
Last weekend I took a picture when it stopped, it showed 12.2V and 40%. Fuel was above half, so plenty of it.View attachment 73209Problem is that with this % it won’t kick off again, when I tried, the battery dropped to 10% (I didn’t take a picture, I think voltage was showing 11.8V) and, after few moments of clicking sounds, the whole system switches off again. I need to start the engine, just 5-10 minutes running, then the battery is showing 100% and I can immediately restart the heater. Note I only keep level 1-2 when it runs as it is warm enough.
Is this its normal way of working? Just 6-7h of hot air, so less than a night sleep? Is it normal that it stops at 12.2V?

Second question: I watched during (seemingly) proper functioning, some time after starting it with engine on, and there’s always a constant consumption of around -4.2A. View attachment 73210Nothing else is on, no fridge, no lights, nothing plugged. Why is that? I thought that after starting it should just run on diesel, not the battery. Is this due to the fan of the webasto? Is -4.2A a normal value? (Then no surprise the battery drops to insufficient level in 6-7h I guess....)

Any tips to get it running longer are appreciated. Anything else I should check? (note both leisure batteries were recently replaced, they’re not as old as the van!)

Thank you very much.
Elisa

If the battery voltage, at anytime drops to 11.5 Volts approximately, the Heater and/or Fridge will Switch OFF to protect the Leisure Batteries . The heater uses electrical power to run the fan and the fuel pump.
If yours are the original Leisure Batteries then they are probably failing.
I had similar after 5.5 years. One battery failed and wouldn't hold charge . The heater wouldn't run over night when wild camping in Norway despite covering 200+ miles during the day. Would run fine on Mains Hookup.
Changed both Leisure Batteries and now it will run for 48hrs plus.

One thing to check before condemning the Batteries - Check that the 50 Amp cube fuse on the +tve pole of the rear Leisure Battery has not failed. If it has then you are running on only 1 Leisure Battery.

If that fuse is OK and these are the original batteries then they probably need replacing after almost 14 yrs.

 

[laeli]

If the battery voltage, at anytime drops to 11.5 Volts approximately, the Heater and/or Fridge will Switch OFF to protect the Leisure Batteries . The heater uses electrical power to run the fan and the fuel pump.
If yours are the original Leisure Batteries then they are probably failing.
I had similar after 5.5 years. One battery failed and wouldn't hold charge . The heater wouldn't run over night when wild camping in Norway despite covering 200+ miles during the day. Would run fine on Mains Hookup.
Changed both Leisure Batteries and now it will run for 48hrs plus.

One thing to check before condemning the Batteries - Check that the 50 Amp cube fuse on the +tve pole of the rear Leisure Battery has not failed. If it has then you are running on only 1 Leisure Battery.

If that fuse is OK and these are the original batteries then they probably need replacing after almost 14 yrs.

Thank you, both leisure batteries are from Oct 2020 (varta F21 silver dynamic 12V, 80Ah, 800A) and it helps me a lot to know that running 48h is a realistic expectation. I will check the fuse -after studying the forum to learn how -
Thank you!

If the battery voltage, at anytime drops to 11.5 Volts approximately, the Heater and/or Fridge will Switch OFF to protect the Leisure Batteries . The heater uses electrical power to run the fan and the fuel pump.
If yours are the original Leisure Batteries then they are probably failing.
I had similar after 5.5 years. One battery failed and wouldn't hold charge . The heater wouldn't run over night when wild camping in Norway despite covering 200+ miles during the day. Would run fine on Mains Hookup.
Changed both Leisure Batteries and now it will run for 48hrs plus.

One thing to check before condemning the Batteries - Check that the 50 Amp cube fuse on the +tve pole of the rear Leisure Battery has not failed. If it has then you are running on only 1 Leisure Battery.

If that fuse is OK and these are the original batteries then they probably need replacing after almost 14 yrs.

Thank you, the batteries are few months old, but I will check the fuse. Thanks for explaining that pump and fan use the battery, any idea whether -4A is a correct consumption for the electric needs of the heater?
Thank you!

It burns diesel to produce heat. Everything else is electric . The fuel pump,the air fans, the glow plug etc. Once burning the glow plug switches off. That is the moment the current draw should drop. Maybe one of your leisure batteries has a blown fuse so your running on 1 battery? The heater should run longer than that on a low heat.

Thank you, the batteries are few months old, but I will check the fuse. Thanks for explaining that pump and fan use the battery, any idea whether -4A is a correct consumption for the electric needs of the heater?
Thank you!

 

[WelshGas]

Thank you, the batteries are few months old, but I will check the fuse. Thanks for explaining that pump and fan use the battery, any idea whether -4A is a correct consumption for the electric needs of the heater?
Thank you!

It can be as the fan and fuel pump vary in speed, both slowing down as the temperature comes up. From my experience, if the temperature setting is low and the heater exceeds that set temperature despite lowering the burn rate of diesel then it switches Off, But the heater light on the Control Panel stays on and the Heater will restart when the cabin temperature falls. The heater fan stays on, but at a very, very low speed as the temperature sensor is in the air intake situated on the driver's step.

 

[laeli]

It can be as the fan and fuel pump vary in speed, both slowing down as the temperature comes up. From my experience, if the temperature setting is low and the heater exceeds that set temperature despite lowering the burn rate of diesel then it switches Off, But the heater light on the Control Panel stays on and the Heater will restart when the cabin temperature falls. The heater fan stays on, but at a very, very low speed as the temperature sensor is in the air intake situated on the driver's step.

Thank you. Very helpful to distinguish normal from faulty operation

 

[bvddobb]

I would still think -4A is a bit much...

To expand on @WelshGas' experience: since the air-intake is also the point where the temp is measured, and since it is located in the door step AND there is a blower outlet blowing towards the door step, if one has e.g. cushions or something on the turned-around chair blocking hot air rising from the footwell, or the room behind the chair is packed with stuff that has been put out of the way there, the temp sensor can think it is quite hot in the car and slow the heater down or turn it off, while the rest of the 'lounge' is still a bit cold.
In the thread on the german Caliboard re. the T6 aux heater being too cold/insufficient, there are people who have closed down the footwell outlet, blowing all the hot air towards the 'lounge', thus fooling the temp sensor in that it generally thinks the car is colder than is actually the case.
Our € 0.02

 

[WelshGas]

I would still think -4A is a bit much...

To expand on @WelshGas' experience: since the air-intake is also the point where the temp is measured, and since it is located in the door step AND there is a blower outlet blowing towards the door step, if one has e.g. cushions or something on the turned-around chair blocking hot air rising from the footwell, or the room behind the chair is packed with stuff that has been put out of the way there, the temp sensor can think it is quite hot in the car and slow the heater down or turn it off, while the rest of the 'lounge' is still a bit cold.
In the thread on the german Caliboard re. the T6 aux heater being too cold/insufficient, there are people who have closed down the footwell outlet, blowing all the hot air towards the 'lounge', thus fooling the temp sensor in that it generally thinks the car is colder than is actually the case.
Our € 0.02

Must have different heater vents then because on mine no heater outlet is directed forward from the B pillar . The output is across the rear of the front seats towards the kitchen or across the sliding door opening towards the bench seat.




As regards the Amps used during operation, it all depends when the measurement is taken, during what stage of heater operation, steady state, sudden drop in temperature when opening door or window. If in steady state mode and door opened then the heater output rises with increased fan speed and increased fuel pump activity momentarily to bring the temperature back up.

 

[bvddobb]

Must have different heater vents then because on mine no heater outlet is directed forward from the B pillar .

Interesting! Perhaps something to do with left hand/right hand drive? We have our passenger seat on the right hand side, and we definitely have a vent in the B-pillar towards the front. It is were we 'tap' the hot air for our air hose towards the 'attic' during cold nights.

I would still think -4A is a bit much...

Just fired ours up in the present cold and let it run for some time. Apart from the firing up sudden high drain, when the heater is heating steadily, our CU reads -3.5 A. So, perhaps in heating mode, -4.0 A isn't that unusual after all... With 2 x 80 Ah batteries, as is standard in a Cali, running down to 50% capacity you would still have 20 hours running of constant heating. It is never constantly heating, it switches off every now and then when the right temperature is reached (unless your thermostat is broken, or something), so you would indeed have 48-72 hours running constantly at least (as is also our experience).

It may still be that you have the shunt earthing issue, it happened in 2007-2008 builds, as it did in ours. Then all readings re. voltage, amperage, charge etc. in the CU are false, and the logic in it may go berserk. I remember us being cold when the heater would switch off in the middle of a winter's night. Since we repaired the shunt, that doesn't happen anymore.

Do your interior lights flicker when the heater fires up? That is a sure sign of the earth shunt issue!

 

[westfalia]

Two vents on mine, both blow out warm air.

 

[bvddobb]

Two vents on mine, both blow out warm air.

Yours is a left hand drive, too, I guess (Germany being your location). Perhaps that explains the difference, somehow.

 

[laeli]

I would still think -4A is a bit much...

To expand on @WelshGas' experience: since the air-intake is also the point where the temp is measured, and since it is located in the door step AND there is a blower outlet blowing towards the door step, if one has e.g. cushions or something on the turned-around chair blocking hot air rising from the footwell, or the room behind the chair is packed with stuff that has been put out of the way there, the temp sensor can think it is quite hot in the car and slow the heater down or turn it off, while the rest of the 'lounge' is still a bit cold.
In the thread on the german Caliboard re. the T6 aux heater being too cold/insufficient, there are people who have closed down the footwell outlet, blowing all the hot air towards the 'lounge', thus fooling the temp sensor in that it generally thinks the car is colder than is actually the case.
Our € 0.02

Thank you. I might be wrong on this but when it switches off due to reached temperature, I have the impression the symbol is still active on the control unit, it looks like a stand-by, the heater isn’t totally silent and it restarts on its own when needed. It does this few times over its 6-7h of “proper” functioning. But then it goes totally off and sure enough it doesn’t restart by itself (when battery is 40% not even when prompted by remote or control units. It tries but fails).
Does yours turn off completely due to the thermostat reading? That might be happening after all. The outlet was free but the car was comfortably warm...

 

[laeli]

Interesting! Perhaps something to do with left hand/right hand drive? We have our passenger seat on the right hand side, and we definitely have a vent in the B-pillar towards the front. It is were we 'tap' the hot air for our air hose towards the 'attic' during cold nights.

Just fired ours up in the present cold and let it run for some time. Apart from the firing up sudden high drain, when the heater is heating steadily, our CU reads -3.5 A. So, perhaps in heating mode, -4.0 A isn't that unusual after all... With 2 x 80 Ah batteries, as is standard in a Cali, running down to 50% capacity you would still have 20 hours running of constant heating. It is never constantly heating, it switches off every now and then when the right temperature is reached (unless your thermostat is broken, or something), so you would indeed have 48-72 hours running constantly at least (as is also our experience).

It may still be that you have the shunt earthing issue, it happened in 2007-2008 builds, as it did in ours. Then all readings re. voltage, amperage, charge etc. in the CU are false, and the logic in it may go berserk. I remember us being cold when the heater would switch off in the middle of a winter's night. Since we repaired the shunt, that doesn't happen anymore.

Do your interior lights flicker when the heater fires up? That is a sure sign of the earth shunt issue!

The earth shunt was my first guess from the age of the van, although the lights don’t really flicker in a noticeable way. I guess one could detect micro-flickering if one really wants to find it...but that is also the case during operation and not just at startup... I’m leaning towards the running on a single battery now...

Either way, all replies here help me to know what to expect from the heater performance once the issue (shunt, fuse, battery) is addressed, so I can tell if the fix worked

 

[laeli]

Must have different heater vents then because on mine no heater outlet is directed forward from the B pillar . The output is across the rear of the front seats towards the kitchen or across the sliding door opening towards the bench seat.

View attachment 73290


As regards the Amps used during operation, it all depends when the measurement is taken, during what stage of heater operation, steady state, sudden drop in temperature when opening door or window. If in steady state mode and door opened then the heater output rises with increased fan speed and increased fuel pump activity momentarily to bring the temperature back up.

Thank you. The -4.2A reading was after maybe 20 minutes of running smoothly, doors closed and -2 degrees outside, but I will look at that more closely at various stages of operation.

I have a vent at the foot of sliding door towards the bench and I have the impression it's the only one...

 

[Emil Silenhag]

First of all, check the sticker in the door, so we know what kind of heater you have. I assume it’s a Webasto AirTop 3500ST (?) which was normal in 2007, but it could be another heater.
4.2A is normal when going full effect (10 of 10).
As mentioned before by some one above, make sure both batteries deliver power to the system.
Then, finally, check the amp reading in the display when starting up. You will se bursts of amps when glow plug is glowing. It will typically start at 17-20 A for 2-3 seconds, the back to 3-4, and new burst slightly lower around 15, and back to 3-4, then new burst 10-15. Those bursts should come 12-15 times. I’ve seen it go bad for some reason. Then those bursts can come up to 30 times. And the heater frequently goes into “sleep mode” (reached the set temperature), and have to start over again and again with new bursts to the glow plug. This is a mail function and will drain batteries prematurely. In those situations I’ve replaced the glow plug and burner, but with no difference !?
Btw the sensor is not in the air duct by the foot well, it is on the control unit which is part of the webasto, in the air flow between the plastic housing and the internal components...I’ve tried a external temp sensor (in the cabin) but that’s another story...

 

[bvddobb]

Btw the sensor is not in the air duct by the foot well, it is on the control unit which is part of the webasto, in the air flow between the plastic housing and the internal components.

What I tried to say was: wherever it sits, it measures the temperature of the air taken in from the foot well.

 

[laeli]

First of all, check the sticker in the door, so we know what kind of heater you have. I assume it’s a Webasto AirTop 3500ST (?) which was normal in 2007, but it could be another heater.
4.2A is normal when going full effect (10 of 10).
As mentioned before by some one above, make sure both batteries deliver power to the system.
Then, finally, check the amp reading in the display when starting up. You will se bursts of amps when glow plug is glowing. It will typically start at 17-20 A for 2-3 seconds, the back to 3-4, and new burst slightly lower around 15, and back to 3-4, then new burst 10-15. Those bursts should come 12-15 times. I’ve seen it go bad for some reason. Then those bursts can come up to 30 times. And the heater frequently goes into “sleep mode” (reached the set temperature), and have to start over again and again with new bursts to the glow plug. This is a mail function and will drain batteries prematurely. In those situations I’ve replaced the glow plug and burner, but with no difference !?
Btw the sensor is not in the air duct by the foot well, it is on the control unit which is part of the webasto, in the air flow between the plastic housing and the internal components...I’ve tried a external temp sensor (in the cabin) but that’s another story...

Thank you. I watched carefully today and the startup of the heater (yes it’s the Webasto) works very much in line with your description which is reassuring: first -15A, then 12 times switching between -2.6A and -14A finally settling to 3.5 at first and steady 2.6 for the next 2 hours.
On the voltage side however it went from 12.8 to 12.3 just with the startup. Percentage going from 100% to 50%.
After 2h all indicators were still the same. Btw it was -2 degrees outside, very windy and I kept the roof up.

 

[laeli]

Now, update on the rear battery exploration: it didn’t go very far as I missed that the battery is screwed to the floor and I didn’t have the right tool with me However I measured across the fuse as in this picture with the arrows that I found here in another thread.
The measure was -0.14V (repeated few times, always same value). Is the fuse blown? Or is this within tolerance and counts as zero? (When I touch the 2 pins, the meter shows a clear 0 though..)

Other 2 elements I find concerning are:
1) the fuse and red terminal are kept in place with duct tape (see pic). this seems a DIY installation, not VW and I’ll try to get more info from the guy who sold me the van
2) I noticed that in other pictures of the control unit here on the forum both battery symbols (top center and bottom right) show identical consumption. In my control unit only the bottom right symbol decreases, the top one is always showing full. Could this be a clear sign of rear battery not being used/connected?

@WelshGas @bvddobb

Thank you all for your useful feedbacks

 

[2008 fresco]

Slightly off topic but I took out the fuse for the Webasto in my 2008 Cali. It turns itself on randomly when driving, once in 95 deg heat in Spain. Might not happen for months then bingo suddenly feels hot...presume it is a control panel problem, but everything fine otherwise with the panel. Tend to take a fan heater & timer switch as am usually hooked up....

 

[Emil Silenhag]

Thank you. I watched carefully today and the startup of the heater (yes it’s the Webasto) works very much in line with your description which is reassuring: first -15A, then 12 times switching between -2.6A and -14A finally settling to 3.5 at first and steady 2.6 for the next 2 hours.
On the voltage side however it went from 12.8 to 12.3 just with the startup. Percentage going from 100% to 50%.
After 2h all indicators were still the same. Btw it was -2 degrees outside, very windy and I kept the roof up.

Okay, then it’s confirmed that it works normally and doesn’t activate the glow plug abnormally often or hard.
Yes, the glow plug is a heavy load for the battery. It’s normal to drop from 12,8 to 12.4 immediately. Then perhaps recover to 12.5 V. But yours lingered on at 12.3 v...? That’s a sign of weak/old/worn battery, or only one battery working (check fuse on battery in the back).

 

[Emil Silenhag]

You need to check the fuse, the white cube-shaped thing on the battery terminal, on the battery under the wardrobe. It has a small window. You can measure it with a multimeter but keep in mind that the positive wire from the battery terminal will have 12 volt even if you remove it from the battery terminal (there’s another battery under the front seat, parallel)...
Check the window on the fuse, with a mirror or just pull out the battery so you also can check thwart they have done with the tape in the picture..?