Webasto Intermittent Operation

[shahzadlateef]

Holiday season greeting all,

I have a 2003 Marathon H3-45 with intermittent Webasto operation. On a typical Las Vegas cold morning (30s), while testing the unit, I turn on 12 V Heat switch and call for heat from thermostats (double push on heat buttons). The unit comes on as it should and the coach starts heating. After about 1-2 hours, I check the coach and Webasto turns off with cold air blowing into the coach. When I try to turn the Webasto back on right away, it starts (motor whirring and cold air from exhaust pipe) but never ignites the diesel heat. After a few minutes the unit turns off as it should with no ignition. If I wait long enough to cool off, the unit starts over just fine, and sometimes stays on cycling on and off as needed for heating.

Same issue when turning on Webasto through 12 V Water Heater. It is a hit and miss.

I had it checked from Marathon in Coburg earlier this year in July, and they saw similar issues. They services the unit and changed out the igniters and it worked fine when they tested it. Next time I tried it after leaving the shop, same intermittent operation started again.

Sounds very much like a control box or sensor type problem. Just checking to see if any of you have thoughts on how to troubleshoot this.

Appreciate the responses.

Regards,

Shahzad Lateef
2003 Marathon H3-45, DS

[PrevostNewbie]

What model Webasto do you have? Check the high temp sensor.

[shahzadlateef]

Thanks Mike.

Should have thought to add the model number. The label is a bit warn out in the picture. I believe it is DBW 2010.74, 24V/60W, 132kW.

High temperature sensor is a good start. I just need to locate it. I don’t have schematics of the unit but I am sure can find it online somewhere. I know of the flame sensor. High temperature sensor makes sense as it runs well when it is cold outside.

Will try that out.

Regards, Shahzad Lateef
2003 Marathon H3-45, DS

[PrevostNewbie]

There are many manuals online, The sensors are easy to get to, i just replaced all 3 of mine.

[twslp]

MINE was coil. had been replaced once before.

[Fratto]

We have run into that before as well. Make sure the fuel pressure is right and if there was anything left in the fuel line or pump, etc. then it likely clogged the new nozzel as well. After we got the fuel pressure right and put in a new nozzle and temp sensors we were good to go. Also double check that they are using the right nozzle. When we picked up the Parliament, the previous serving firm put in the wrong nozzle and had the fuel pressure way to low.

If you keep the bus for awhile, you can buy the pressure gauge and the testing box for about the same money as an annual pm.

There are other threads on POG where folks have had bad bearings that heated up and slowed down the speed of the unit but fortunately that was not our problem.

[Fratto]

Here is an ebay link to a Louisville Engineering tester for $279.00 that will work. If you scroll down this page a little bit you will see the pressure gauge for $115.00. I have seen others in the past in a similar price range but I know this one works.

https://www.ebay.com/itm/26576719274...3ABFBMtuyR3Khh

[shahzadlateef]

Thanks all. I will get sensors changed out and see if that resolves it before buying the test apparatus. I figure that the test apparatus may not catch sensor issues as it completely bypassed the Webasto controller.

Pulled out three sensors and ordered new ones. I know it is not the overheat fuse because it had been shorted. I have included pictures below. There is no inspection detailed enough that will catch something like this. The sensor is $30, so I don’t know why someone will bypass this important feature.

Will let everyone know of the outcome.

Regards, Shahzad Lateef
2003 Marathon H3-45, DS

[PrevostNewbie]

Thanks all. I will get sensors changed out and see if that resolves it before buying the test apparatus. I figure that the test apparatus may not catch sensor issues as it completely bypassed the Webasto controller.

Pulled out three sensors and ordered new ones. I know it is not the overheat fuse because it had been shorted. I have included pictures below. There is no inspection detailed enough that will catch something like this. The sensor is $30, so I don’t know why someone will bypass this important feature.

Will let everyone know of the outcome.

Regards, Shahzad Lateef
2003 Marathon H3-45, DS

This is the test box I use. It doesn't bypass the Webasto controller it goes in it's place and allows you to control the system right there at the unit. There is a light that will tell you if your thermostats are bad.

https://www.suremarineservice.com/He.../5011070A.html

[shahzadlateef]

Thanks Mike. I will replace the sensors any way as they are fairly cheap and easy to replace. If that doesn’t solve the issue, I will get the test box and troubleshoot further. Just felt like the test box for end user is a fairly limited application tool.

Regards, Shahzad Lateef
2003 Marathon H3-45, DS