Webasto heater heats well past set point?

A

Almanac

Well-known member
Joined
Oct 13, 2020
Messages
48
Fluid Motion Model
R-21 EC
Vessel Name
Fool's Mate
I have a 2021 C-28, I don't believe my Webasto heater has ever worked properly. It heats just fine, but the problem is when I set the temperature it heats past the temperature.

Tonight, I tested it by setting the temperature to 65 F. I checked back later and it was 88 F as read on the Smartemp display. Last weekend I set the temperature very low, like 50 F and I did see it turn off. So it is capable.. but if I set the temperature at anything reasonably 60 F or higher, it seems it just heats the boat continuously.

I recently replaced the Smartemp 2.0 controller with Smartemp 3.0 controller hoping that it would fix the issue, but it still happens. Diagnostics didn't return any failure codes.

Does anyone have any troubleshooting tips or know what's going on?

Below is a picture from the new controller's bluetooth app. Please note that I had the same problem on the Smartemp 2.0 controller before I upgraded to the bluetooth model. I was hoping this would fix the problem.

 
Hello Almanac -

I also installed the Webasto 3.0 SmarTemp controller replacing the 2.0 controller and encountered similar issues on my 2020 R-29 CB with a Webasto EVO 40 heater. However, my 2.0 controller did seem to read the correct ambient temp of the boat at the location of the controller.

In your display example of the 3.0 bluetooth app I see it's showing the ambient temp of 88 degrees F which is unlikely.....that reading should be the temp at the location of the 3.0 controller, that's where the sensor is located is my understanding. It appears the reading of the 88 degrees on the app is taking a reading near the Webasto heater, similar to what I was encountering.

I ended up sticking with the 2.0 controller, although everything else on the operation of the 3.0 controller worked fine (except ambient temp reading) and the bluetooth app and diagnostics are nice features to have.

Marc Doyle
2020 R-29 CB / Puffin
Port Ludlow, WA
 
Marc,

I had the same issue with my previous controller. I didn't have another thermometer on board to check the cabin temperature, but it felt very warm and I believed the 88 F reading. It is actually heating to 88 F.
 
Hi all,

Guess that's something I probably would never complain about. :lol: I like it warm...

But seriously though, looks like this might be an issue for Webasto to address. It is most likely a software issue and should be able to be handled with a software update. Make sure you have the latest version installed on your app and check for any updates. If that doesn't make any difference, it will be time to reach out to Webasto. Hope this helps for now.

Cheers,

Ralf
 
I have had the exact same problem with my Webasto Smartemp 3.0 with Blue Tooth as well. However, I do show an error message that states "The set point potentiometer circuit is faulty" When I email Webasto about this, I got the following email reply: When receiving this code “setpoint potentiometer” the issue is either a wiring problem or may be the controller itself. I replaced the original Rheostat controller last fall, with the new Smartemp 3.0. I have placed another thermometer next to the Smartemp, and can tell when the Smartemp is inaccurate. The webasto under control of the Smartemp seems to continue running past the temperature I have it set for. Colby
 
Another reply from Webasto when I told the rep about this thread and my problem again:

... this could be the mounting location of the SmarTemp within the space. There are no software updates available for the SmarTemp 3.0. I have attached the operation manual for the SmarTemp 3.0 for review. Please make sure that the yellow wire is plugged in and fully seated into the ECU next to the main connector at the heater. This yellow wire tells the heater to use the SmarTemp 3.0 for temperature reading rather than the internal sensor behind the fan inside the ECU.
 
Colby,

Thanks for the information. I think this will help us get somewhere that we are both having the same issue. Do you also have the Webasto AT 2000 STC heater?

Please make sure that the yellow wire is plugged in and fully seated into the ECU next to the main connector at the heater. This yellow wire tells the heater to use the SmarTemp 3.0 for temperature reading rather than the internal sensor behind the fan inside the ECU.
Click to expand...

I am going to be working on the boat today and I will see if I can find the Webasto ECU and check on this. Last night when I was working on the boat I set the temperature to 55 F and it was about 70 F in the cabin. Sometimes it does seem to stop, just much higher than the set point. I can believe that it is taking a temperature at the fan, especially if the intake is from below the mid-berth area, where it is cooler.

I had called Webasto tech support line yesterday, but I did not get the same information. The tech basically told me it was the controller or the ECU and if I replaced the controller it must be the ECU. I was hoping he would tell me something exactly like what you heard about checking the status of a specific wire.

- Alan
 
I didn't get to dig into the heater completely this weekend, only a little. First off, I was wrong, I do not have a Webasto AT 2000 STC. I have an EVO 40 heater, which is a bigger model than the 2000 STC. My Smartemp was incorrectly set to 2000 STC in the setup, so I updated it and ran another test.

I set the temperature to 72 because it was reading in the mid 60s, and turned it on. The Smartemp controller temperature climbed quickly to 72, 74, 80F, etc. I only have a laser infrared thermometer on the boat. It's a bit difficult to know the best way to measure the temperature as the surface temperatures of object in the cabin likely won't increase as quickly as the controller's temperature did. I was measuring in the high 60s on many objects after ~20 min. The heater kept running. I checked the diagnostic.

The diagnostic said the set temp point was 22 C (~72F) which is where I had it set. However it measured the Temperature as 17 C and never got higher than 20 C in about 20 minutes or so that I had time to test it. The Smartemp controller was reading something much higher 85 F. But, it didn't feel 85 F in the cabin. The laser infra thermometer was measuring high 60s surface temperatures and maybe 70 F. However, when I pointed it at the Smartemp controller the infrared thermometer measured the Smartemp's temperature at the same temperature as the controller was reading (~85F). There's nothing that should be generating heat near the Smartemp controller other than itself. Pointing the laser at the intake to the Webasto heater underneath matched the 17-20C temperature reported in the app.

I had gotten access to inspect the heater by removing a couple panels in the mid berth, port-side. Mainly, I just saw the body of the heater and the model number but I didn't have time to dig into it further. Later tonight, I found a video which shows the installation of this yellow wire for the external temperature sensor. I also found this on the wiring diagrams from Webasto:
https://www.youtube.com/watch?v=fXsVLpaZr2U

If I had known I could have popped off the cover and checked for whether this wire was plugged in, I would have done it. Unfortunately, I had to do some other work today and will have to check it another night this week.

If I had to guess right now, I believe that my yellow external temperature sensor is not plugged in and the unit is using the internal temp. I also believe the Smartemp controller is reading too high because it is somehow generating its own heat. I'm going to see if I can connect that yellow wire if it is not plugged in, and then run some more tests and potentially adjust the Smartemp's relative temperature down (which I believe is adjustable +- 10 degrees).
 
Re: Webasto heater heats well past set point?
Postby Almanac on Sat Mar 25, 2023 1:01 pm
Colby,
Thanks for the information. I think this will help us get somewhere that we are both having the same issue. Do you also have the Webasto AT 2000 STC heater?
...
I had called Webasto tech support line yesterday, but I did not get the same information. The tech basically told me it was the controller or the ECU and if I replaced the controller it must be the ECU. I was hoping he would tell me something exactly like what you heard about checking the status of a specific wire.
- Alan
Click to expand...

Hello Alan,
Yes, I do have the Webasto AT 2000 STC heater. I have found different techs give different answers. When I first installed my Smartemp 3.0BT, I was replacing the original Rheostat. So I also had to get the correct wiring harness. The harness I received had a different plug on it than what would fit the heater's harness. One tech told me that the harness was the correct one. I called back later, speaking to a different tech, and after telling me the same thing, with my continuing to explain the problem to him admitted that not all the heaters had the same plugs. In my case we decided I could cut the plugs off and "hard wire", connecting the proper wires together between the harnesses. I believe there were just two wires, and according to the tech one was the data wire, the other a common (ground) wire. However, there was a yellow wire with a separate plug, and those plugs between the two harness's mated. I did double check that connection and they are connected. However, due to my installation, I can not get to the ECU of the unit to see if that yellow wire is connected there. I will have to pull the heater out to get to the top to pull the cover off to check. Before I do that, I plan to use a heat gun on a very low setting to check the temp readout on the Smartemp 3.0, and on the app. (I will also place another thermometer right next to the smartemp to compare temperatures.) My heater seems to work sometimes as it should, but other times it'll continue running past the temp set. Colby
 
Colby,

I was able to get to the heater and remove the cover and sure enough, my yellow wire was not connected. I have connected it and I believe it is using the Smartemp Ambient Temp. sensor now. In addition, I have also adjusted the Smartemp Controller's relative temperature by about -8 F because I found the Smartemp Controller was higher temperature than ambient.

I don't have a video of the test I did afterwards, unfortunately, but I will continue to test it in the coming weeks.

Here's a video of some footage I took and plugging in the wire:
https://www.youtube.com/watch?v=nCo5VLzD93I
 
Alan -

Thanks for sharing video...very interesting and you're quite the acrobat to get access to the Webasto EVO 40...not sure why the 3.0 controller would register the high temp reading as displayed on your temp gun with surrounding temps well below....you said the controller was not warm to the touch.

Also, I believe in your initial post you had your SmarTemp bluetooth app set for the AT 2000 STC and not the EVO 40....have you changed the app setting?

Now with the yellow wire connected to the Webasto EVO 40 is the heater shutting off once you reach the set temp and is your 3.0 controller displaying the correct ambient temp with the adjustments you made on the app?

Marc Doyle
2020 R-29 CB / Puffin
Port Ludlow, WA
 
I'm assuming it's just poor design on the Webasto controller. The LEDs or electronic components near the ambient sensor must be giving off heat. I've adjusted the relative temperature on the controller to help compensate. It would be interesting to test it with a small fan, e.g. computer fan, blowing on the front of the device and see if that makes the temperature converge to ambient. I have updated the setting to the EVO 40.

The three changes I made:

1. Corrected the app to use the EVO 40 setting to match my heater model
2. Plugged in the yellow wire as shown in the video, behind the cover on the heater
3. Set the Smartemp temperature to -8 F to compensate for the higher ambient temps on the device.

I tested it afterwards and it was working better. I saw the unit cycle off as expected. I still want to run some longer tests where I leave the heater running for a couple hours.
 
Finally accessed my Webasto EVO 40 heater located on the port side under the NovaKool refrigerator which was removed to allow access to heater unit. Accessing the Webasto wire connection cover was a bit of a challenge.....once it was popped off I could see the yellow temp sensor wire/plug was not connected to the heater. Removed the gray plug cover and inserted the yellow wire plug.

Ran the SmartTemp 3.0 bluetooth controller and app and now started obtaining ambient temp readings in line with the actual cabin temperatures within 2 to 3 degrees.....made the adjustment on the app to reflect the difference. The Webasto performed appropriately and once the set temp was reached the unit seemed to cycle off to maintain set temp.

Here are pics of the Webasto EVO 40 unit on a 2020 R-29 CB:

https://www.icloud.com/iclouddrive/0fbk ... _40_Medium

https://www.icloud.com/iclouddrive/09f6 ... ire_Medium

https://www.icloud.com/iclouddrive/0f3X ... ensor_Wire
 
Nicely done, I wonder how many of these have been missed!
 
I pulled my webasto heater out a few days ago to not only check on that yellow wire, but to clean it as well. In my case, the yellow wire was plugged in. After cleaning it, putting it back together, and reinstalling it all, I did stop getting the error message about the potentiometer. However, the ambient temperature is still reading about 10 degrees high. That requires the maximum temperature offset in settings. I just don't think it should read off that far.
 
I don’t think I could call my control switch a thermostat. At best, it does low, medium and high. And really on off is all it’s really capable of. I will follow this thread, however, it’s unlikely needed given how little I use the heater, I can justify the effort. It would be great if someone would find the easy button fix. 😀
 
A follow up. I ended up getting a new controller as a warranty replacement. It seemed to work for a short time, but I'm back to getting the error message, "The set point potentiometer circuit is faulty". I pulled the heater and wiring harnesses all out of the boat so that I could access them. I have checked the continuity on smartemp 3.0 wiring harness, and there are no shorts. (Webasto tech said that with some other readings in the diagnostic readout in the app, this would indicate a short.) My webasto heater does not have the single yellow wire that plugs in next to the main wiring harness connector, but rather the yellow wire is in a pin on that main harness connector. Then on the other side of the heater where there are several plugs, there is one with two yellow wires going into the plug, and the other ends of both wires appear to go inside the intake chamber before the burner chamber. Sometimes the ambient temp readout on the smartemp controller is accurate (with an offset of -5), other times it's 10-15 degrees f hotter than actual temp. Webasto tech said that webasto allows a variance of 2-3 degrees centigrade, or 6-8 degrees F. I'm still working with Webasto Tech to try and figure this thing out.
 
Plus one for connecting the yellow wire. We have a June 2021 build R31.

I removed the fridge today to access the Evo 40 webasto unit. Remove the grey cover from the unit and found the yellow wire not connected. Next pried the black rubber plug out and plugged the yellow wire into the unit. Reinstalled the grey cover and fridge.
We have the smart 3.0 Bluetooth controller. Turned on the controller and adjusted the heat to 71. After the heat reached 71 the unit turned off and once the temp dropped one degree under set point the heater turned back on.The outdoor temp was 45 today.
I have the temp offset at -2 right now but may adjust it after we have an overnight trip.
So good to have this working so well now. In the past we would have to have the temp set to 58 or less at night otherwise it would be roasted out. Thanks for the the tugnuts that experimented with this before I did. Fix took less than an hour.
 
Plus one more for the yellow wire on a pandemic build '21 C-28. The Evo 40 unit was right there in the cave where you said it would be with the yellow wire just waiting to be plugged in. Thank you all for this most helpful thread. Hope to not cook guests again on chilly fall mornings.

One question about the install location. Where is the unit getting breathing air, that is for combustion and to blow on board? The panels were pretty snug in the cave.
I can only think of the loose fitting shower sump panel and the bow thruster panel. Am I missing something?

Fred Juhos
Blue J-2 C-28
Edmonds, WA
 
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