Webasto Smartemp 3.0 controller

colbysmith · Posted: Sun Oct 08, 2023 11:08 pm Post subject: Webasto Smartemp 3.0 controller

I am having issues with my Webasto's Smartemp 3.0 controller and wonder if anybody else has one and is experiencing this. Many times the controller will show a temperature 5 to 10 degrees warmer than what the ambient air temp is. Also, the heater will many times continue heating past the set temp. Ie, temp set for 64, but heater continues to heat the cabin to 70+. Running the diagnostics on my smartphones Smartemp app, I come up with an error code 9Bh and message stating: "The Set Point Potentiometer Circuit is Faulty." I had this issue earlier, and under warranty exchanged for a new controller. It seemed to work correctly for a short time, but now back to the same problem. I'll work with Webasto again on this, but didn't seem to resolve this issue last time I talked with them. Googling, some have talked about making sure the yellow wire is plugged in the controller board on the heater. I checked that, and mine is.

colbysmith · Posted: Sun Oct 29, 2023 10:14 pm Post subject:

Still having issues with my smartemp 3.0 controller for my Webasto heater. Have several messages into Webasto tech and hope they can end up making this an easy fix. I have pulled the heater out of the boat, along with all the wiring. I have gone through all the wiring harnesses, checking for continuity of each wire, and also making sure there are no shorts between wires. Again, the error code I am seeing is:

Error 1: The set point potentiometer circuit is faulty.
The element has an interruption or a short circuit to UB

Also with in the diagnostic report, it's showing:
Code 9Bh

In earlier conversation with Webasto tech, I was told that the error means there could be a short in the wiring, the Smartemp controller itself, or maybe even the ECU. Since this is the second smartemp (replaced under warranty), he said it would be highly unlikely that I had two bad controllers, but possible.

The wiring harness that was required to add the smartemp 3.0 to my Webasto Airtop 2000 STC heater has 4 wires. Red for power, brown for ground, yellow for the temp sensor in the smartemp, and yellow with a green stripe for data. The smartemp pigtail has two additional wires, a gray for brake input (not needed for the heater since it's not installed in a truck or RV), and black, for heater on/off signal. The main wiring harness at the heater, has the black wire in the connector to the smartemp harness, but the smartemp harness does not have that black wire. I'm wondering if that's part of the problem, but the harness is what's provided by Webasto.

Kind of out of ideas until I talk again with Webasto hopefully tomorrow!

Peter & Judy · Posted: Mon Oct 30, 2023 10:49 am Post subject:

I have the same system installed both in my C-Dory and in my truck Camper. I have never had an problems with them. They are excellent units and really well designed and made. But, my trouble shooting thoughts would go to the controller and then the wiring harness and finally to the heater itself. The controller should be easy to swap out and try again. Then the wiring harness would be my next step. I would try to install a new harness without all of the wire pulling through the various nooks and crannies of the boat. Finally if all else fails, then I would install a new heater onto the old harness and controller. This might be the only way that you can precisely determine if the problem is in one of these three components. It is quite possible with all the different wiring in your boat, vibrations from travelling and boating that a wire shorted out and is causing the problem.

I had a shorted wire harness on my tractor caused by vibrations. I could not solve the problem myself, so I took it into Case. The technician spent 16 hours at $125/hr looking for the problem and 1 hour fixing the problem. Part of the problem was that the short was at the back of the tractor and he started looking at the front.

After installing my Wabatso heater, new electronics, stereo speakers and other electrical upgrades in my boat, I have decided to buy a small monkey and train him to do any future wiring. I had considered having the bones removed from my arms, but my doctor recommended not doing this.

Best of luck trouble shooting the heater.

colbysmith · Posted: Mon Oct 30, 2023 11:26 am Post subject:

Hello Peter,
Yes, a trained monkey might be the answer. Very Happy

At this point, I don't believe it is in the wiring. I have gone through all the wiring between the webasto heater and the smartemp controller, and all wiring between the heater and the power fuses, and again in the original wiring from the heater to where the original rheostat plugged in. No shorts, and good continuity throughout. (The heater came with the rheostat initially. I upgraded it to the smartemp and have had problems since.) I replaced the smartemp once already under warranty. And may have to do that again. It is the easiest thing to get to and change out. But I have all the wiring and heater out now, so the harness would be the next best thing to change out, since it came with the first new controller and would be under that warranty I believe. The heater is no longer in warranty, but it appears to work just fine. The error code speaks to the smartemp controller, and the only part in the heater that could possibly have an effect would be the ecu, which could be changed out while I have the heater out. The rheostat seemed to be working in regards to the heater when I removed and upgraded it to the smartemp, but the rotary dial on it was failing. That leads me to believe it's in the wiring harness or the smartemp, and the wiring harness seems to be fine. (Assuming that the black wire for heater on/off signal is not needed and not suppose to be in the harness...) I'm too cheap to take it in to a Webasto dealer/shop to do what I think I can do myself. Sad

I've got the time after all, but the frustration level is building... Colby

Peter & Judy · Posted: Mon Oct 30, 2023 1:02 pm Post subject:

colbysmith · Posted: Mon Oct 30, 2023 4:56 pm Post subject:

The mercury bubble might work.. Mr. Green

I spoke with a different tech at Webasto today. He thinks that it's possibly an issue in the connections somewhere. He stated that they see a lot where the main harness is not seated all the way in at the ECU in the heater. I know mine is seated all the way in as there is a little plastic tab that has to snap into the indent. I added some electric grease at all the connections. I've had a few issues in other electronics where the humidity in the boat caused some corrosion. It was only 33 F (0 C) out mid morning, but with the sun shining and the cover bringing in some heat, I installed the heater and wiring back in the boat. I'll turn the heater on tomorrow and run it during the day to see if I get the error code again. (Waiting until tomorrow, so that the high temp silicone I used at the exhaust pipe fitting can set up.) Colby[/list]

Robert H. Wilkinson · Posted: Mon Oct 30, 2023 10:35 pm Post subject:

colbysmith · Posted: Mon Oct 30, 2023 11:44 pm Post subject:

Actually I used Ox Gard anti oxidant compound. Colby

colbysmith · Posted: Tue Oct 31, 2023 11:02 pm Post subject:

Ran the heater for 7 hours today, with no error codes. Before reinstalling the heater and wiring, I cut the wires in the harness to the original rheostat, since that is no longer hooked up and that harness was not being used. I did place connectors on both ends so that if I ever needed to hook that harness back up, I could. But it reduces the amount of wiring coiled up in the heater area. I also added some wires and moved the connectors between the smartemp harness and the main harness, so that they were accessible without pulling the heater out. All connectors had ox-gard anti-oxident compound used, and connections double checked for integrity. I'm hoping this solved the errors and occasional erroneous temp readings. Time will tell.... Colby